understanding engineering geology

Luwalaga John Groover

MSc.PH (IHSU); B.Eng. Civil (KYU); H.Dip. Civil (KYU); Dip. Arch. (UPK)

2010 Edition

2 KYU, DCBE, BENG. CBE 2 & BEEEM 2, Engineering Geology Notes, for Sem.2,

2010/2011.

©Luwalaga John Groover (Mob: 0772450847; E-mail: [email protected])

KYAMBOGO UNIVERSITY

FACULITY OF ENGINEERING

DEPARTMENT OF CIVIL AND BUILDING ENGINEERING

CE 225: ENGINEERING GEOLOGY

FOR

B.ENG. CBE II AND BEEEM II

FEBRUARY 2011


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Table of Contents

CHAPTER ONE ................................................................................................................................... 9

1.0 INTRODUCTION ............................................................................................................... 9

1.1 Brief Description of the course ................................................................................ 9

1.2 Objective of the course ................................................................................................ 9

1.3 Geology ............................................................................................................................... 10

1.4 Work of Geologist ....................................................................................................... 10

1.5 The Scope of Geology .............................................................................................. 10

1.5.1 Physical geology ........................................................................................................ 10

1.5.2 Historical Geology .................................................................................................... 11

1.6 Civil Engineering ......................................................................................................... 12

1.7 Engineering Geology ................................................................................................. 12

1.8 Why study Geology .................................................................................................... 12

1.9 Activities of Engineering Geologists in Civil & Building Engineering

Industry ............................................................................................................................ 13

CHAPTER TWO ................................................................................................................................. 14

2.0 THE PLANET EARTH AND ITS SURROUNDING .............................................. 14

2.1 Universe ........................................................................................................................... 14

2.2 The Solar System ........................................................................................................ 14

2.3 The Planet Earth ......................................................................................................... 19

2.4 The Age of the Earth ................................................................................................ 20

2.5 The Internal Structure of the Earth .................................................................. 20

2.5.1 Crust ................................................................................................................................. 22

2.5.2 Mantle .............................................................................................................................. 22

2.5.3 Core .................................................................................................................................. 22

2.6 The Theory of Plate Tectonics ........................................................................... 23


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2.7 Continental Drift ........................................................................................................ 23

2.7.1 Evidence Supporting Continental Drift .......................................................... 24

2.8 Sea-Floor Spreading ................................................................................................. 25

Formation of an Oceanic Ridge ............................................................................................. 25

2.9 Geological Time Scale ........................................................................................................... 26

CHAPTER THREE ............................................................................................................................ 28

3.0 MINERALOGY .................................................................................................................. 28

3.1 INTRODUCTION ........................................................................................................... 28

3.2 SUMMARISED UGANDA MINERAL INVENTORY AND THEIR USES .. 29

3.3 Identification of Minerals and their Properties .......................................... 36

3.3.1 Physical Properties of Minerals .......................................................................... 36

3.3.2 Microscopic Optical Properties of Minerals......................................... 42

3.3.3 Chemical Properties of Minerals ........................................................................ 44

CHAPTER FOUR .............................................................................................................................. 50

4.0 PETROLOGY ...................................................................................................................... 50

4.1 Definitions ...................................................................................................................... 50

4.2 Rock Cycle ..................................................................................................................... 50

4.3 Types of Rocks ............................................................................................................ 52

4.3.1 Igneous Rocks (Eruptive Rocks) ....................................................................... 52

4.3.2 Sedimentary Rocks/Stratified/Secondary Rocks .................................... 56

4.3.3 Metamorphic Rocks .................................................................................................. 60

CHAPTER FIVE ................................................................................................................................. 63

5.0 STRUCTURAL GEOLOGY ............................................................................................ 63

5.1 Definitions ...................................................................................................................... 63

5.2 Folds .................................................................................................................................. 64

5.2.1 Causes of Folding ...................................................................................................... 64

5.2.2 Parts of a fold and connected terminology ................................................. 65


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5.2.3 Types of Folds ............................................................................................................. 68

5.2.4 Engineering Considerations involved in Dealing with Folded

Rocks ............................................................................................................................................ 70

5.3 Fractures in Rock ...................................................................................................... 71

5.3.1 Joints ................................................................................................................................ 72

5.3.2 Faults ............................................................................................................................... 73

CHAPTER SIX ................................................................................................................................... 77

6.0 EARTH QUAKE ................................................................................................................. 77

6.1 Definition ......................................................................................................................... 78

6.2 Causes of Earthquakes and their types ......................................................... 78

6.3 Seismic waves ............................................................................................................. 79

6.4 Types of seismic waves................................................................................. 80

6.4.1 Body waves: .................................................................................................................. 80

6.4.2 Surface waves .............................................................................................................. 80

6.5 Measuring of the size of an Earthquake ......................................................... 81

6.5.1 Intensity: ......................................................................................................................... 81

6.5.2 Magnitude: ...................................................................................................................... 81

6.6 Effects of earthquakes ............................................................................................ 83

6.7 Tsunami: .......................................................................................................................... 85

CHAPTER SEVEN ............................................................................................................................ 86

7.0 GEOTECHNICAL METHODS OF SITE INVESTIGATION .............................. 86

7.1 Definitions ...................................................................................................................... 86

7.2 Objectives ....................................................................................................................... 86

7.3 Steps involved in Site Investigation ................................................................. 87

7.3.1 Desk study ...................................................................................................................... 87

7.3.2 Site reconnaissance. ................................................................................................ 88

7.3.3 Ground investigation ................................................................................................ 88


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CHAPTER EIGHT ............................................................................................................................. 91

8.0. TUNNELING .............................................................................................................................. 91

8.1 Definitions. ..................................................................................................................... 91

8.2 Merits and demerits of tunnels. ......................................................................... 91

8.3 Tunnel approaches .................................................................................................... 92

8.4 Shape and size of tunnel cross-sections. ...................................................... 93

8.4.1 Shapes of tunnel cross-section ......................................................................... 93

8.4.2 Size of Tunnel cross-section. ..................................................................... 96

8.5. Types of tunnels ................................................................................................................ 96

a) Traffic tunnels. ................................................................................................................... 96

b) The Hydro power tunnels. ............................................................................................ 97

c) The Public Utility Tunnels ............................................................................................ 98

8.6 Geological considerations required for successful tunneling

operations in consolidated and unconsolidated rocks. ......................... 98

8.6.1 Tunneling in consolidated rocks ....................................................................... 98

8.6.2 Tunneling in unconsolidated rocks ................................................................. 99

CHAPTER NINE .............................................................................................................................. 100

9.0. PROCESS OF WEATHERING AND DENUDATION ................................................ 100

9.1 Introduction: General, sources and definitions ........................................ 100

9.2 Types of weathering. .............................................................................................. 101

9.2.1 Mechanical weathering or disintegration ................................................... 101

9.2.2 Chemical weathering. ............................................................................................ 103

9.2.3 Biological Weathering ............................................................................................ 107

9.3 Agents of erosion ...................................................................................................... 108

9.3.1 Water ............................................................................................................................... 108

9.3.2 Wind ................................................................................................................................. 108

9.3.3 Erosion by moving ice. .......................................................................................... 108


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9.4 Factors affecting rate of Weathering ............................................................. 109

9.5 Importance of weathering ................................................................................... 110

9.6 Short coming of weathering ............................................................................... 110

CHAPTER TEN ................................................................................................................................ 111

10.0 GEOLOGICAL ASPECTS OF BUILDING STONES AND

AGGREGATES. ............................................................................................................................... 111

10.1 Introduction ................................................................................................................ 112

10.1.1 Rock ........................................................................................................................ 112

10.1.2 Stone ....................................................................................................................... 112

10.2 Uses of stones .......................................................................................................... 112

10.3 Seasoning of stone ................................................................................................. 113

10.4 Characteristics of stones ................................................................................... 113

10.5 Decay or degradation of Stones ...................................................................... 114

10.6 Preservation of stones ......................................................................................... 115

10.6.1 Examples of preservatives ................................................................................ 115

10.7 Quarry and Quarrying ............................................................................................ 116

10.8 Selection of Quarry site ....................................................................................... 116

10.9 Different methods used in stone Quarrying .............................................. 116

CHAPTER ELEVEN ....................................................................................................................... 118

11.0 GEO-HYDROLOGY ....................................................................................................... 118

11.1 Origin of ground water. .......................................................................................... 118

11.2 Definition...................................................................................................................... 119

11.3 The hydrologic cycle. ............................................................................................ 119

11.4 Occurrence of Groundwater .............................................................................. 120

Porosity ...................................................................................................................................... 121

Permeability ............................................................................................................................ 122

Water table .............................................................................................................................. 124


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Perched water table ........................................................................................................... 124

Drainage of Ground water ............................................................................................... 124

Specific yield .......................................................................................................................... 124

Specific retention or field capacity ............................................................................ 125

11.5 Wells ................................................................................................................................ 125

11.5.1 Types of wells .................................................................................................... 125

11.6 Aquifers. ........................................................................................................................ 127

11.6.1 Types of Aquifers ............................................................................................. 128

11.7.1 Formation and types of springs ................................................................ 131

11.8 Isotropy and Anisotropy ........................................................................................ 132

11.8.1 Isotropy (KV = KL) ................................................................................................ 132

11.8.2 Anisotropy (KL >>>>> KV) ..................................................................................... 132

11.9 Potentiality of different Rocks as Aquifers ............................................... 132

11.9.1 Sedimentary rocks as aquifers. ................................................................ 132

11.9.2 Metamorphic Rocks as Aquifers. ............................................................. 133

11.9.3 Igneous Rocks as Aquifers.......................................................................... 133

11.10 Groundwater Prospecting .................................................................................... 133

11.10.1 Objectives of hydro-geological investigation ................................ 134

11.10.2 Methods of exploration ............................................................................. 134

11.10.3 Logs or recording of Bore-hole Data .................................................. 136

BIBLIOGRAPHY ............................................................................................................................. 149


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CHAPTER ONE

The ancient Romans had a tradition: whenever one of their Engineers constructed an arch, as the capstone was hoisted

into place, the Engineer assumed accountability for his work in the most profound way possible: he stood under the arch.

Michael Armstrong. U.S. business executive, speech

1.0 INTRODUCTION

1.1 Brief Description of the course

Introduces the fundamental aspects of geological processes and materials.

Examines the close linkage with our everyday life as well as with civil and water engineering

constructions of common good.

1.2 Objective of the course

By the end of this course (Engineering Geology) students should be able to:

Describe and identify the different types of rocks in order of formation and their physical

properties;

Observe and record geological information and then translate this data to practical

engineering design, construction and maintenance of civil engineering projects;

Explain the rocks’ contributions to groundwater quality purification and deterioration;

Identify the chemical, mineralogical composition and structures of these rocks and their

effects to construction structures;

Identify groundwater flow pattern within the different types of rocks in the world;

Describe fully and identify the biological properties the rocks offer to weathering processes.

Definition of Geology

Work of Geologist

The Scope of Geology

Definition of Civil Engineering

Definition of Engineering Geology

Why study Geology

SUMMARY


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1.3 Geology

The term Geology comes from the Greek words Geo + Logos. Geo means Earth, and

Logos means study or science. Geology therefore, deals with the study of the planet

Earth on which we are living. The science of Geology tells us about the origin, structure

and history of the Earth and its inhabitants, as recorded in the rocks. Without its

study, one remains ignorant about the same planet on which we are living.

Geology is a branch of natural science devoted to the study of the physical features of

the earth, the composition and structure of the rocks composing it, the forces at work

in altering it, and the record of the animals and plants that have lived on its lands and

inhabited its seas.

1.4 Work of Geologist

Geologists seek to understand how the earth formed and evolved into what it is today,

as well as what made the earth capable of supporting life.

A geologist is concerned with every aspect of the composition and structure of the

earth’s crust. His/her sphere of work is therefore world-wide; his/her main laboratory

is the great out-of-doors where he/she examines rocks as they actually occur in

nature. His/her considerations range from the beginning of time and into the future,

even to that time when man will no longer be on earth. He/she studies all that

composes the crust of the earth sphere and especially those materials of use to his/her

fellow man.

1.5 The Scope of Geology

The scope of geology is so broad that it has been split into two (2) major divisions:-

1. Physical geology

2. Historical geology

1.5.1 Physical geology

It deals with the Earth’s composition, structure, the movements within and upon the

Earth’s crust, and the geologic processes by which the Earth’s surface is, or has been

changed. This division of geology includes in itself, the following branches:-

Mineralogy: - This deals with the study of minerals. Minerals are basic constituents

of rocks, and thus, influence the properties of the rocks. Hence in order to know the

properties of the rocks, one has to study the properties of the minerals.


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Petrology: - The term Petrology is derived from the Greek word, Petro + Logos. Petro

means rocks and Logos means study. Hence Petrology means the study of the rocks.

Since the Earth’s crust, also called lithosphere (solid outer layer of the Earth above

the asthenosphere, consisting of the crust and upper mantle), is composed of different

types of rocks, their study is done under this branch, which deals with the study of

mode of formation, structure, texture, composition, occurrence, types, etc. of the

various rocks of the Earth’s crust.

Structural Geology: - The rocks which constitutes the Earth’s crust, have undergone

and continues to undergo various deformations, dislocations under the influence of

tectonic forces; causing formation of geological structures like folds, faults, joints, etc.,

in the rock masses. The details of their mode of formation, causes, types, classification,

importance, etc, are studied in this branch of physical geology.

Geomorphology: - This branch of geology explains and studies the origin of various

surface features of the Earth.

Economical Geology: - This is a specialized division of mineralogy and petrology,

wherein the products of the Earth’s crust having good economic value, are studied.

Valuable ores containing metals, like coals, petroleum, etc, do come under the domain

of this specialized study. It includes the study of their occurrence, search, and

exploitation for commercial and industrial uses.

1.5.2 Historical Geology

This deals with the study of the origin and evolution of the Earth and its inhabitants.

The various sub-divisions of this branch of geology includes:-

Stratigraphy: - The term stratigraphy comes from the Greek words: Strata + Graphy.

Strata mean the sets or beds of sedimentary rocks; while Graphy means the

description. Stratigraphy deals with the study of the beds of the sedimentary rocks.

The study thus helps in identifying the ages of the rocks of the various regions and

areas, thereby assisting in describing in detail their general civil engineering uses. The

study of these rocks involves extraction of fossils, i.e. the remains of plants and

animals of the past geological Eras.

Palalentology: - Deals with the study of the ancient organisms, plants, and animals,

etc; as revealed from their remains and remnants (i.e. fossils), the study helps in


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providing a background to the development of life on Earth, over the past geological

Eras.

Palaeogeography: - This branch of science deals with the study of the geographic

conditions of the past times. It, thus deals with the reconstruction of the relations of

the ancient lands and seas, and the organisms that inhabited them.

1.6 Civil Engineering

Civil Engineering is defined as the art that includes the design and construction of all

structures other than simple buildings, and the investigation, design, and

construction of all systems of transportation, natural power development, water

supply and sewage disposal, as well as the direction of natural forces for the use and

convenience of man. Every branch of civil engineering has some contact with the

surface of the earth. For instance, the works designed by the civil engineer being

supported by or located in some part of the earth’s crust. The practice of civil

engineering includes the design of these works and the control and direction of their

construction.

1.7 Engineering Geology

Engineering geology is the application of engineering principles to geologic problems.

Two fields of Engineering that use geology extensively are civil Engineering and Mining

geology Engineering. For example, the stability of a building or bridge requires an

understanding of both the foundation material (rocks or soil) and the potential for

earthquakes in the area.

1.8 Why study Geology

To classify and know the types of rocks

To differentiate the types of minerals and their properties

To appreciate geological structures such as faults, folds, joints, bedding, etc

To determine the strength and behavior of geological materials

To be able to understand and carryout ground investigations

To understand the earth’s endogeonetic and exogeonetic processes e.g. weathering,

erosion, failure of slopes, etc

To be able to interpret Geological Maps

To understand characteristic of ground water bodies


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To facilitate excavations in rocks and soils during mining, tunneling, etc

To be able to determine foundations and embankments for reservoirs, dams, etc

To help identify suitable locations for landfills

1.9 Activities of Engineering Geologists in Civil & Building

Engineering Industry

Investigation of foundations for all types of major structures, such as dams, bridges, power plants, airports, large buildings and towers; Evaluation of geological ground conditions along tunnels, mines, pipelines, canals, railway, and highway routes; Exploration and development of sources of rock, soil and sediment for use as construction material; Investigation and development of surface and groundwater resources; groundwater basin management; protection and remediation of groundwater resources; Evaluation of geological hazards such as landslides, faults and earthquakes, seismic hazards, radon, asbestos, subsidence, expansive and collapsible soils, expansive bedrock; The evaluation of geological conditions affecting residential, commercial, and industrial land use and development; Foundation investigation, slope stability and excavatability; The safe disposal of waste to the Earth; In cooperation with the civil engineers, Engineering geologists have a big role in ensuring public safety, health and welfare in relation to engineering works. In some countries like the US, the profession laws require participation of engineering geologists in approving construction plans. Geology is pro-people. It exists because people want to modify the geological environment for their use and convenience; they want to work and live safely in harmony with the environment. Geologists can determine which geological environment is good and safe for construction.


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CHAPTER TWO

John 1:1-4

In the beginning the Word (Jesus Christ) already existed. The Word was with God, and the Word was God. He existed in

the beginning with God. God created everything through Him and nothing was created except through Him. The Word

gave life to everything that was created, and His life brought light to everyone.

2.0 THE PLANET EARTH AND ITS SURROUNDING

2.1 Universe

The Universe is the totality of all matter and energy that exists in the vastness of

space, whether known to human beings or not.

2.2 The Solar System

The solar system (sun and bodies orbiting it) is the sun and all the planets,

asteroids, meteors, and comets that are subject to its gravitational pull.

The Solar System

The Planet Earth

The Age of the Earth

The Internal Structure of the Earth

The Theory of Plate Tectonics

Continental Drift

Sea – floor spreading

Geological Time Scale

SUMMARY


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The Solar System consists of nine major planets (including the earth) moving around

a central body – SUN.

These planets includes:-

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.

The nine major planets and their moons (32) are revolving in nearly the same plane

around the sun. In addition to this movement around the sun, these planets are

undergoing constant rotation about their own axis. Among the nine planets, only the

earth is the only planet which is certainly known to support life.

2.2.1 Important Facts about the Solar System

No. Name of the

Planet

Average distance

from the sun

(million Km)

Equatorial

Diameter (Km)

No. of

Moon

Length of time

for 1 trip around

the sun

Length of time for 1

revolution about the

own axis

1 Mercury 57.91 4878 0 88 days 59 days

2 Venus 108.2 12100 0 224 days 243 days

3 Earth 149.6 12756-

12714

1 365 ¼ days 23hrs, 56min,

1sec.

4 Mars 227.94 6793-6753 2 1.9 years 24hrs, 37min

5 Jupiter 778.33 142880-

133540

12 11.9 years 9hrs, 50min

6 Saturn 1426.98 120000-

106900



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7 Uranus 2871 50800-

49400

5 84 years 10hrs, 49min

8 Neptune 4497 48600-

47500


9 Pluto 5914 5500 0 248 years 6.4 days

Mercury orbits closer to the Sun than any

other planet, making it dry, hot, and virtually

airless. Although the planet’s cratered surface

resembles that of the Moon, it is believed that

the interior is actually similar to Earth’s,

consisting primarily of iron and other heavy

elements. This composite photograph was

taken in 1974 by Mariner 10, the first probe to

study Mercury in detail.

Venus is the brightest object in our sky, after

the sun and moon. Swirling clouds of sulfur

and sulfuric acid obscure Venus’s surface and

inhibited study of the planet from Earth until

technology permitted space vehicles, outfitted

with probes, to visit it. These probes

determined that Venus is the hottest of the

planets, with a surface temperature of about

460° C (about 860° F). Scientists believe that

a greenhouse effect causes the extreme

temperature, hypothesizing that the planet’s

thick clouds and dense atmosphere trap energy

from the sun.


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Earth. An oxygen-rich and protective

atmosphere, moderate temperatures, abundant

water, and a varied chemical composition

enable Earth to support life, the only planet

known to harbor life. The planet is composed

of rock and metal, which are present in molten

form beneath its surface.

Mars. The most detailed information available

about Mars has come from unpiloted

spacecraft sent to the planet by the United

States. From this data, scientists have

determined that the planet’s atmosphere

consists primarily of carbon dioxide, with

small amounts of nitrogen, oxygen, water

vapor, and other gases. Because the

atmosphere is extremely thin, daily

temperatures can vary as much as 100 Celsius

degrees (190 Fahrenheit degrees). In general,

surface temperatures are too cold and surface

pressures too low for water to exist in a liquid

state on Mars. The planet resembles a cold,

high-altitude desert.

Jupiter is the largest of the planets, with a

volume more than 1,300 times greater than

that of Earth. Jupiter’s colorful bands are

caused by strong atmospheric currents and

accentuated by a dense cloud cover. The

massive planet, upper right, is shown here

with its four largest satellites: Io, upper left,

Ganymede, lower left, Europa, center, and

Callisto, lower right.


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Saturn, distinguished by its rings, is the

second largest planet in the solar system. This

processed Hubble Space Telescope image

shows the planet’s cloud bands, storms, and

rings as they would appear to the human eye.

Uranus. Uranus’s blue-green color comes

from the methane gas present in its cold, clear

atmosphere. The dark shadings at the right

edge of the sphere correspond to the day-night

boundary on the planet. Beyond this boundary,

Uranus’s northern hemisphere remains in a

four-decade-long period of darkness because

of the way the planet rotates.

Neptune. This image of Neptune, taken by the

Voyager 2 spacecraft, shows the planet’s most

prominent features. The large, dark oval

surrounded by white clouds near the planet’s

equator is the Great Dark Spot, a storm similar

to Jupiter’s Great Red Spot. The smaller dark

oval with a bright core below and to the right

of the Great Dark Spot is another storm known

as Dark Spot 2.


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2.3 The Planet Earth

Earth (planet), the third planet in distance from sun in the solar system, the only

planet known to harbor life, and the home of human beings

Nearly two-thirds or about 71% of earth’s surface is covered by water, which is

essential to life. The rest is land, mostly in the form of continents that rise above the

oceans.

Pluto is farther from the Sun than the

major planets in the solar system,

although it occasionally moves in closer

than Neptune due to an irregular orbit.

The small, rocky, and cold world takes

247.7 years to revolve around the Sun.

This artist's rendition depicts Pluto,

foreground; its moon, Charon,

background; and the distant Sun, upper

right.


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Illustration of the earth

North Pole

Polar (12714 Km)

Equator (12756 Km)

Circumference (40, 000 Km)

South Pole

The earth has a Polar diameter of 12714 Km, Equatorial diameter of 12756 Km,

Circumference of 40,000 Km; surface area of about 510 x 106 Km2, volume of about

1042 x 109 Km3, mass of about 5.97 x 1021 tones; average distance from the sun is

150 x 106 Km, length of time for one trip around the sun is 365 ¼ days, length of time

for one revolution about the own axis of about 24 hours and average temperature of

14oC. In shape, the earth is like an oblate spheroid, i.e. with the exception of a slight

flattening at the poles, the earth is nearly spherical or ball shaped.

2.4 The Age of the Earth

Geochronologists are responsible for determining the age of the earth using

radioactivity technique (radiometric dating technique). This can be achieved by using

modern estimates of the age of rocks which form the earth’s crust and are based on

determinations on radioactive minerals contained in the rocks. The age of the earth

has been estimated to be about 4.55 billion years.

2.5 The Internal Structure of the Earth

The known volume and mass of the earth gives its mean density to be 5.5 g/cm3, yet

the mean density of rock forming the outer part is 1.126 and 3.1 g/cm3. Thus its

greatest mass is concentrated towards the centre.

Evidence from seismic waves shows that the earth is layered. The earth basically

consists of 3 layers:-

1) Crust

2) Mantle

3) Core


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The Earth is made up of a series of layers that formed early in the planet’s history, as

heavier material gravitated toward the center and lighter material floated to the

surface. The dense, solid, inner core of iron is surrounded by a liquid, iron, outer core.

http://upload.wikimedia.org/wikipedia/commons/e/ee/Earth-crust-cutaway-english.svg


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The lower mantle consists of molten rock, which is surrounded by partially molten

rock in the asthenosphere and solid rock in the upper mantle and crust. Between

some of the layers, there are chemical or structural changes that form discontinuities.

Lighter elements, such as silicon, aluminum, calcium, potassium, sodium, and

oxygen, compose the outer crust.

2.5.1 Crust

This is a solid rock which is the topmost thin layer of the earth’s body, having a solid

thickness of about 30 to 40 Km in continents and 5 to 6 Km in the oceans. In fact, it

has been concluded that in the continents, the total depth is about 35 Km, out of

which the bottom 5 Km depth consists of denser Basalt rock (density of 3.0 g/cm3);

and the top 30 Km consists of lighter Granite rock (density of 2.7 g/cm3).

The granitic rocks of the continents and the basaltic rocks of the oceans are covered

by a top layer of unconsolidated sediments (about 1 Km thick). The earth’s crust

provides hard and soft rocks, and is classified as igneous, sedimentary and

metamorphic rocks which are to be discussed later.

2.5.2 Mantle

This is a region surrounding the heavy core. The mantle consists of upper mantle

which is generally solid and the lower mantle which is semi-solid and can flow; and

this is the focus of most earthquakes.

The crust and the uppermost part of the mantle are relatively rigid and collectively

they make up the lithosphere. The lower mantle which is below the lithosphere is

called the asthenosphere, which is soft and therefore flows more readily than the upper

mantle. It provides a lubricating layer over which the lithosphere moves.

2.5.3 Core

This consists of 2 layers (inner and outer core). The inner core is solid and is composed

of heavy metals mainly iron (Fe) and Nickel.

The outer core consists of the same metals but in a fluid state.

Magnetism is generated by the electric currents flowing through the liquid iron (Fe).

Therefore the earth has its own magnetic field.


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http://www.youtube.com/watch?feature=endscreen&v=0mWQs1_L3fA&NR=1

2.6 The Theory of Plate Tectonics

The term Plate Tectonics came to be used to denote the process involved in the

movements and interactions of the plates (“tectonic” is derived from Greek “tekton”,

meaning a builder).

Plate Tectonic is a theory that outer shell of the Earth’s surface is divided into large,

thick, rigid plates that are slowly moving relative to each other, and changing in size.

The plate tectonic theory is a unifying theory that accounts for many seemingly

unrelated geological phenomena. Some of the disparate phenomena that plate

tectonics explains are where and why we get earthquakes, volcanoes, mountain belts,

deep ocean trenches, and mid-oceanic ridges.

Plate tectonics regards the lithosphere (crust and upper mantle) as broken into plates

that are in motion. The plates, which are much like segments of the cracked shell on

a boiled egg, move relative to one another, sliding on the underlying asthensphere

(lower mantle).

According to plate tectonics, divergent boundaries exist where plates are moving apart;

transform/conservative boundary occurs where two plates slide past each other,

earthquakes along the fault are a result of plate motion; and convergent boundary

occurs where plates move toward each other.

http://www.youtube.com/watch?v=1-HwPR_4mP4&feature=related

http://www.youtube.com/watch?v=KCSJNBMOjJs&feature=related

2.7 Continental Drift

The planet Earth is composed of about six continents namely, Africa, North America,

South America, Asia, Europe, and Australia.

http://www.youtube.com/watch?feature=endscreen&v=0mWQs1_L3fA&NR=1

http://www.youtube.com/watch?v=1-HwPR_4mP4&feature=related

http://www.youtube.com/watch?v=KCSJNBMOjJs&feature=related


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The continents at one time about 220-250 million years (my) ago, formed one super-

continent called “Pangea” or “Pangaea”.

Continent drift is the idea that continents move freely over Earth’s surface, changing

their positions relative to one another.

From the study of magnetism in the rocks of the earth’s crust and from the detailed

surveys of the ocean floor; it was concluded in 1960s that continents

drifted/drift/move away from one another.

2.7.1 Evidence Supporting Continental Drift

1) Palaeo-climatology: The past climates which are inconsistent with their modern

locations.

2) Palaeontology: Patterns of present day animal life, similarities among fossils across

continents.

3) Geometric fit of the different continents e.g. if South America and Africa are fitted

together, the identical contacts are found in precisely the right position on the

shore of South America.

4) Matching Stratigraphy and Truncated structure: The Mountains of North Eastern

America, Western Europe and Northern Africa, their compositions are the same

and this is a proof that the world was one.


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2.8 Sea-Floor Spreading

Sea-floor spreading is Hess’s 1962 proposal which is a hypothesis (concept) that the

sea floor forms at the crest of the Mid-oceanic ridge, the moves horizontally away from

the ridge crest towards an oceanic trench. The two sides of the ridge are moving in

opposite directions like slow conveyor belts.

Mid-ocean ridges occur along boundaries between plates of Earth’s outer shell where

new seafloor is created as the plates spread apart. As plates move apart under the

ocean, molten rock, or magma, wells up from deep below the surface of the seafloor.

Some of the magma that ascends to the seafloor produces enormous volcanic

eruptions. The rest solidifies on the edges of the plates as they spread apart, creating

new rocky seafloor material.

Formation of an Oceanic Ridge

An oceanic ridge develops on the ocean floor where the boundaries of tectonic plates

meet. Molten rock is forced up at these boundaries and pushes the oceanic crust up

and outward, creating the ridge.

Magma Upwelling

Mid-ocean ridges occur along boundaries between plates of Earth’s outer shell where

new seafloor is created as the plates spread apart. As plates move apart under the

ocean, molten rock, or magma, wells up from deep below the surface of the seafloor.


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Some of the magma that ascends to the seafloor produces enormous volcanic

eruptions. The rest solidifies on the edges of the plates as they spread apart, creating

new rocky seafloor material.

2.9 Geological Time Scale Geologic time is the time scale that covers earth’s entire geologic history from its origin

to the present day.

Geology involves vastly greater amounts of time, often referred to as deep time. The

earth is estimated to be about 4.55 billion years old. Humans have been here only

about the last 3 million years.

Geologic time scale helps scientists think about the history of the planet in

manageable section of time. Geologists can use fossils in rocks to refer the age of the

rock to the standard geologic time scale (below), a worldwide relative time scale. Based

on fossil assemblages, the geologic time scale subdivides geologic time.


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Geologic Time Scale

EON ERA PERIOD EPOCH BEGINNINGLIFE FORMS

ORIGINATING

(YEARS AGO)

Neogene Holocene (Recent)…11500……………………………………………

(Quaternary) Pleistocene…………..1.8 million……………Human…………………. Cenozoic Paleogene Pilocene………………5.3 million…………………………………………. (Tertiary) Miocene……………….23 million……………Grazing and…………. Oligocene……………..34 million……………Carnivorous………… Eolene…………………..56 million…………..Mammals………… ………………………….Paleocene………………65 million………………………………………. Phanerozoic Cretaceous…………………………………145 million….Primate, flowering, plant Mesozoic Jurassic…………………………………………200 million……………..Birds………………… Triassic …………………………………………251 million………Dinosaurs, Mammals Perimian…………………………………….299 million……………………………………….. Carboniferous Pennsylvanian…….318 million………………Reptiles……… Paleozoic Mississippian……359 million………..Fern Forests…………. Devonian………………………………………416 million….Amphibians, Insect……. Silurian……………………………………….444 million..Vascular land plants……. Ordovician…………………………………….488 million….Fish, Chordates…………. Cambrian………………………………………542 million….Shell fish, Trilobites…… Proterozoic………………………………………………………………………………..2.5 billion…….Eukaryotic cells……….. Archean ………………………………………………………………………………………… 3.8 billion? ....Prokaryotic cells…….. The geologic time scale, representing an extensive fossil record consists of three eons

(Archean, Proterozoic and Phanerozoic). Each eon is subdivided into eras. Each era is

made up of periods, which are further divided into epochs. The Archeon and

Proterozoic eons are collectively called Precambrian time. Precambrian denotes the

vast amount of time that proceeded the Paleozoic era (which begins with the Cambrian

period). The Paleozoic era (meaning old life) began with the appearance of complex life,

as indicated by fossils. Rocks older than Paleozoic contain few fossils. This is because

creatures with shells or other hard parts, which are easily preserved as fossils, did not

evolve until the beginning of the Paleozoic. The Mesozoic era (meaning middle life),

followed the Paleozoic. We live in the recent (or Holocene) epoch of the Quaternary (or

Neogene) period of the Cenozoic era (meaning new life).


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CHAPTER THREE

The Lion looked at Alice wearily. “Are you animal – or vegetable – or mineral?” He said, yawning at every other word.

Lewis Carroll (1832 - 1898), British writer and mathematician.

3.0 MINERALOGY

3.1 INTRODUCTION

Mineralogy is the study of minerals.

Minerals are the basic constituents of rocks, and thus influence the properties of the

rocks.

A mineral is a naturally occurring homogeneous solid with a definite chemical

composition and highly ordered atomic arrangements.

A mineral is a body produced by the process of nature, having a definite chemical

composition and, if formed under favorable conditions, a certain characteristic,

molecular structure which is exhibited in its crystalline form and other physical

properties.

Definitions

Summarized Ugandan Minerals Inventory and their uses.

Identification of Minerals and their properties.

Physical properties

Microscopic Optical properties

Chemical properties

SUMMARY


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3.2 SUMMARISED UGANDA MINERAL INVENTORY AND THEIR USES

Map of Uganda showing all districts


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ITEM MINERAL

COMMODI

TY

DISTRICIT LOCATION USAGE

1 Aggregates

and Crushed

Stones.

All Districts Construction of Houses, Roads and other Civil works.

2 Asbestos Arua

Anzaiya

Roofing, Brakes and Friction, Ceramics, Chemicals and Fertilizers,

Paint, Coatings Vanish, Gaskets, Insulation Mats.

Moroto

Morungore

Nakapiripirit Nakiloro

3 Beryllium Busheny

Kaharoro, Murali, Mutaka.

Beryllium – Copper Alloys with great fatigue resistance nuclear field,

Aeronautic Industry.

Mbarara

Kihanda

Mukono

Lunya

Rukungiri Bugangari, Bulema,

Kyanymphiha, Ishasha,

Nyabushoro,

NyabuKarina.

4 Bismuth Rukungiri Muramba, Kayonza, Rwanzu,

Kyambeya, Kitwa, Rwenkuba,

Kitawulira.

Medical, Cosmetic, Low – Melting point alloys when combined with

Lead, Tin, Cadmium and Antimony, Bearing Alloys with Brass and

Bronze.


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5 Chalcopyrite Kasese Kilembe Copper wires, Coins, Alloys like Brass and Bronze production. Copper

Salts used in Industries like treatment of Timber and Fungicide.

6 Kyanite Rukungiri Ihunga Hill

Nebbi Azi

7 Clay Widely spread in the country

close to swamps river valleys

and rift valleys.

Bricks, Tiles Ceramic Ware.

8 Cobalt Kases Kilembe Used in the form of Ferrous and Non – Ferrous Alloys, special Steels,

also as the oxide and in Salts, Glass and Ceramics, Chemical and Bio

Chemical Industry.

9 Copper Kasese Kilembe Wide applications in Electrical and Metallurgical Industries.

Karamoja

10 Chromites Moroto Nakiloro Manufacture of Metallurgical products, Refractory used in

Metallurgical Plants. Cements and Plastics used in the construction of

Furnaces, Chemical Products such as Chromates and Pigments. Kitgum Burukung and Abora Rivers.

11 Diatomite Nebbi Panyango, Alui, Atar. Chemicals and Fertilizers, Filter Medial e.g. Brewing Industry,

Ferrites, Insecticides, Herb/Fungi. Pakwach

12 Feldspar Mukono Lunya Ceramics, glass, Glazes, enamels, pottery, poultry grit.

Bushenyi Mutaka

13 Glass Sand Masaka Bukakata, Diimu. Glass ware, Enamel ware, Refractories, Scouring and Polishing Media,

Plastics, Rubber, Dental Products, Construction etc.

Wakiso Entebbe

Mpigi Nalumuli, Kome Island

Mukono Nyimu

14 Graphite Kitugum Omia, Orom Hills Lead pencils, Batteries Crucibles, Finer Grade used as Lubricant.

Nebbi Zeu

Moroto Ekuyen

15 Gold Bushenyi Mashonga, and Buhweju.


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Busia Amonikakinei, Makina, Alupe,

and Nanguke.

Jewellery and Decorative, Electronics, Bullion, Monetary, Dental,

Medical, and Industrial Supplies.

Mbarara Ibanda, Mabonwa – mpasha,

Rukiri, and Katenure.

Kanungu Kanungu

Moroto Rupa

Kotido Lopedo, and Alerek.

Arua Most Streams at DRC Boarder.

Nebbi Nyagak River, Goli hill.

Bugiri Bude – Kitojha.

Moyo Most Streams at Sudan Boarder.

16 Gypsum Mbarara Mburo Ceramics, Glass, Glazes, Enamels, Chemicals Cement Manufacture,

Building wall and Wall Board, Soil Container, Textiles, in Casting and

Moulds. Bundibugyo Kibuku

Kasese Muhokya

17 Nickel Mbarara Kajunzo

Ntungamo Rugaga

18 Kaolin Bushenyi Mutaka Ceramics, Chemicals, Construction, Glass, Glazes, Enamel,

Insecticides, paint, coatings, Vanish, Paper, Leather Tanning,

Refrectories, Welding Electrodes. Rakai Kisai (Koki)

Moyo Lunyenye

Nebbi Kuluva

18 Lead/Galena Kabalore Kitaka Used in Battery manufacture, Low Melting point Alloys, Paint, and

Glass.

20 Lime Stone Kasese Hiima Cement, Lime, Ceramics, Chemicals and Fertilizers, Lime used in Soil

Stabilisation, Water Treatment, Poultry and Animal Feed stuffs. Tororo Tororo Hiill

Mbale Bukiribo

Moyo Gweri Hill

Kabarole Dura

21 Lithium Mubende Used in Glass Industry, Enamels, Fluxes, Greases, Bleaches.

Kabala

22 Magnetite Moroto Lolung Making Rubber, Stucco, Magnesium, salts, Heat Insulation Metallurgy

and Refractories.


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23 Marble Kotido Cement, Terrazzo, Dimensional Stone.

Moyo

Moroto Forest Reserve, Tank Hill, Rupa,

Katike Kakile.

24 Malachite Kasese Kilembe Minor ore of Copper used as Ornamental and Gemstone.

25 Mica Arua Chere River Electrical and Heating Insulation e. g. in Flat – Iron, Welding

Electrodes, Plastics and Rubber, Cosmetic and Pharmaceuticals. Kotido Labwor and Morulem

Nebbi Aguyi and Aliakira

Kitgum Orom, and Pailma.

Mukono Lunya.

26 Niobium

(Columbium

)

Tororo Sukulu Useful for its corrosion resisting properties at high temperature such

as in Superchargers and Gas Turbines, in Mild and Stainless Steels,

used in Dyes for Artificial Fibres. Rukungiri Bulema

Kanungu

27 Phosphate Mbale Busumbu Fertilize and Chemicals based on elemental Phosphorus and

Phosphoric Acid, Livestock Food. Tororo Sukulu

28 Precious

Stone

Karamoja Ornamental

29 Pyrite Kasese Kilembe Manufacture of Sulphuric Acid, as a Gemstone old as Marcasite.

30 Salt Kasese Lake Katwe Source of common salt (Sodium Chloride) and a wide range of other

salts e. g. Sodium Carbonate and Bicarbonate, Potassium Chloride,

Sodium Sulphate, Potassium Bromine; Eutectic Brine, Bromine Gas,

used in preservation of Foods, Medicines, and Weed killer.

Masindi Kibiro

31 Talc Kasese Kisinga Cosmetic and Pharmaceuticals, Paper, Carpet backing Ceramics,

Paint, and Refractories. Bushenyi Kyamuhunga

Moroto Lolung

32 Tantalum Rukungiri Very high corrosion resistance and therefore a substitute for platinum

in Chemical apparatus Surgical Steels, used in Dyes for Artificial

Fibres. Bushenyi

Mubende

33 Tin

(Cassiterte)

Mbarara Kikagati – Kitezo, Ruhama,

Ruzinyo.

Tin metal, Alloys, Tin Plating, Canning, Utensils, Textile Dying,

Ceramic Industry, and manufacture of Solders.

Kabale Ruhuma, Buvama, Kamwezi.


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Ntungamo Kyamugasha.

Kanungu

Bushenyi Kaina and Rwentobo.

34 Tungsten

Wolframite

Rakai Buyaga Main use is in high – speed outing tools, Military hardware (Amour

Plate), Electric Light Filament, Electrical Contacts and Tungsten

Carbide. High speed cutting Tools, Steel, Valves, Springs, Armour

Plates and manufacture of resistant Non – Ferrous Alloys.

Kabala Nyamulilo, Mpororo, Rushanga,

Ruhizha.

Masaka

35 Diamond Bushenyi Buhweju

36 Travertine

(Lime Stone)

Kabalore Dura Manufacture of Decorative Terrazzo, Concrete blocks, Ceramics,

Cement, Lime Stone, used in soil Stabilisation, Paints, Water

Treatment, Fertilizer, Building White Wash, Stone, Road Metal,

Whiting substitute and Paper Mills, Neutralization of Waste Acid,

Waste Treatment, Poultry and Animal Feed Stuff.

37 Vermiculite Mbale Namakhara, Sukusi, Kabatola,

Surumbusa, Nakhupa.

Used in Heat and Sound Insulation, Insecticides, Light weight Bricks,

Building Plaster, Lubricants, Brake Linings and Soil Conditioning.

38 Water Widely spread in the Country

except in the in the Rift Valley.

Drinking.

39 Zircon Moroto Rupa Gemstones, Refractory and source of Zirconium Oxide used in the

manufacture of Incandescent Gas Mantles and Abrasive.

40 Iron Ore Mbarara Mugabuzi Roofing Sheets, Iron Bars, and Iron ore is added to Scrap material in

Steel production at Jinja. Kabala Butare (Muko)

Tororo Sukulu

Kisoro Kyanyamuzinda

Moyo Gweri (Metuli)

Iganga Wambogwe.


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3.3 Identification of Minerals and their Properties

Every individual mineral has a certain set of properties, which will be characteristic of

that mineral alone. By testing a mineral for all such properties, therefore, we can easily

identify it.

The various properties of the minerals, the study of which may help in their identification

are:-

1. Physical properties

2. Microscopic optical properties

3. Chemical properties

3.3.1 Physical Properties of Minerals

The physical properties of minerals are important aid in identifying and characterizing

them.

The various physical properties of minerals are: - streak, colour, luster, hardness,

cleavage, fracture, tenacity, specific gravity, etc.

Colour

The first thing most people notice about a mineral is its colour. For some minerals, colour

is a useful property. Muscovite mica is white or colourless. Most naturally occurring

minerals contain traces of substances which modify their colour. Thus Quartz, which is

colourless when pure, may be white, grey, pink, or yellow; when certain chemical

impurities or included particles are present.

Streak

The streak of a mineral is the colour of its powder. The streak of a mineral can be readily

observed by scratching it on a streak plate, which is made up of unglazed porcelain or

roughened glass. Streak plate has a hardness of about 7.0 and cannot be used for

minerals of greater hardness and transparent minerals. While determining streak for a

mineral, care should be taken to scratch it from its obscure part, and to give only a small

scratch, producing a small quantity of its powder. Streak is useful, e.g. in distinguishing

the various oxides of iron like: - hematite (Fe2O3) gives a red streak; Limonite (hydrated

Fe2O3) gives a brown streak, and Magnetite (Fe3O4) gives a grey streak.


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Luster

The shine of a mineral is called its luster. Luster can also be defined as the appearance

of a mineral surface in reflected light. The luster of a mineral is described by comparing

it to familiar substances.

Different Types of Luster

No Type of Luster Represented by Mineral examples

1 Vitreous Luster A mineral having a glassy shine Quartz and Calcite

2 Pearly Luster A mineral having a pearly shine Muscovite

3 Metallic Luster A mineral with a metallic shine Magnetite

4 Silky Luster A mineral with a silky shine Asbestos

5 Resinous Luster A mineral with a greasy shine like that

of a resin

Talc

6 Adamantine

Luster

The mineral having a diamond like

shine

Diamond and Zircon

Cleavage

Cleavage is the ability of a mineral to break, when struck along preferred direction. The

planes along which the crystal breaks are called the cleavage planes. A mineral tend to

break along certain planes because the bonding between atoms is weaker there. In

Quartz, the bonds are equally strong in all directions; therefore, Quartz has no cleavage.

The Micas, however, are easily split apart into sheets. Terms used to describe cleavage

include: - perfect, good, distinct, imperfect and no cleavage.

Different Types of Cleavage

No Type of cleavage Represented by Mineral Example

1 Basal cleavage There are one set of cleavage. The

crystals with this cleavage can easily

break or split into thin sheets.

Muscovite

2 Prismatic cleavage There are two sets of cleavage. The

cleavage planes are parallel to the

vertical set of crystal faces.

Hornblende


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3 Cubic cleavage There are three sets of cleavage at

right angles to each other.

Galena

4 Rhembohedral

cleavage

There are three sets of cleavages

directions, each excellent but at

angles other than right angle.

Calcite

5 Octahedral cleavage There are four sets f cleavage. The

cleavage planes are parallel to the

faces of the crystal form.

Fluorspar and

Magnetite.

Fracture

This is the appearance or nature of a broken surface of a mineral when it is hammered

and broken. The break being irregular and independent of cleavage; a fresh fracture

shows the true colour of a mineral.

Different Types of Fractures

No. Type of

Fracture

Represented by Mineral Example

1 Even Fracture When the broken surfaces of a

mineral is smooth.

Chert

2 Uneven Fracture When the mineral breaks with very

rough and coarse surface.

Chromite and various

other minerals.

3 Hackly Fracture When a mineral breaks with

irregular surfaces having sharp

edges.

Native Copper

4 Earthy Fracture When the broken surface is soft

and almost smooth.

Chalk

5 Conchoidal

Fracture

When a mineral breaks with

curved surfaces. There will be

concentric grooves and ridges

resembling with the concentric

lines of growth on a shell.

Quartz


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Tenacity

The response of a mineral to a hammer below, to cutting with a knife and to bending is

described by its tenacity.

Different types of Tenacities of Minerals

No. Type of Tenacity Represented by Mineral Example

1 Sectile When the mineral can be cut with a

knife. These are very soft minerals.

Talc and Graphite

2 Malleable When a mineral flattens into a sheet,

when hammered. It can also be cut

with a knife as sectile mineral.

Silver and Gold

3 Brittle When a mineral crumbles to grains or

powder, when hammered. Most of the

minerals are brittle in nature.

Quartz, Fluorite,

Calcite, Magnetite,

etc.

4 Flexible When a mineral can be easily bent. Chlorite

5 Elastic When a flexible mineral on being bent,

does regains its original position, as

the bending force is removed.

Muscovite and

Biotite

6 Inelastic When a flexible mineral on being bent,

does not regains its original position,

as the bending force is removed.

Gypsum

Specific Gravity (Gs)

Specific gravity of a substance is the ratio of its weight to the weight of air equal volume

of water at 4oc. H20 has Gs of 1.0.

To determine this, property, a balance can be used, for crystals or fragments which are

not too small. The mineral (or rock) is weighed in air and in water, and the specific

gravity, Gs, is calculated from the formula: W1/ (W1-W2), where W1 = weight in air and

W2 = weight in water.


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Mineral possessing heavier and closely spaced atoms will have high Gs; whereas, a

mineral possessing lighter and widely spaced atoms will have a low Gs. The Gs of the

mineral is thus, a representation of its atomic structure.

Light Gs<2:0, Normal Gs = 2 to 4, Heavy Gs= 4 to 6, extremely heavy Gs>6

Specific gravity of common minerals

Mineral Specific gravity

Hematite 4.9 - 5.3

Magnetite 5.17

Hornblende 3.2 - 3.5

Kugite 3.2 - 3.4

Biotite 2.8 - 32

Micas 2.7 – 3.1

Muscovite 2.7 - 3.1

Chlorite 2.6 - 2.9

Dolomite 2.85 - 2.87

Calcite 2.72 - 2.90

Talc 2.70 - 290

Sermentive 2.20 - 2.70

Quartz 2.65

Cypsum 2.32

Feldspar 2.56 - 2.7

Hardness

Hardness of a mineral may be defined as the resistance which the mineral offers to

scratch. This property of a mineral is generally determined by scratching a given mineral

with a mineral of known hardness, so as to obtain the comparative figure for the

hardness of the given mineral.


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Moh’s scale

The Moh’s scale is used to rate the relative hardness of a material by performing scratch

test and hardness, or resistance to abrasion, is measured relative to a standard scale of

ten minerals, and known as moh’s scale of hardness as seen below. These minerals are

chosen so that their hardness increases in the order 1 to 10.

Moh’s Scale of hardness

Hardness H Mineral

1 Tale Can be scratched with a finger nail.

2 Gypsum

3 Calcite Can easily be cut with a pen knife or scratched by copper coin

4 Fluorspar Can easily be scratched with a knife blade or window glass

5 Apatite

6 Feldspar Can be scratched with a pen knife but with difficulty

7 Quartz Scratches a knife blade or window glass cannot be scratched

with any ordinary

Implement. Quartz will scratch glass; topaz will scratch quartz

will scratch quartz; corundum will scratch topaz and Diamond

will scratch corundum

8 Topaz

9 Corundum

10 Diamond

The numbers given are used as relative hardness numbers, relative only since the actual

hardness value of talc is about 0.02, whereas that for a diamond runs into the

thousands.

Other miscellaneous properties

Besides the above physical properties of minerals, there are others like:

a) Transparency (minerals capability to pass light through it)

b) Fluorescence (is due to which mineral may emit light when exposed to radiations like

x-rays).

c) Phosphorescence ( is due to which mineral may emit light after it has been exposed

to certain radiations or subjected to heating or rubbing)


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d) Taste, feel, odour (all depending upon the senses); fusibility (depending on heat),

magneticity (depending upon the magnetic capability) electrical conductivity (such

as good conductor or bad conductor)

3.3.2 Microscopic Optical Properties of Minerals

Apart from physical properties of mineral, there are several other characteristics of

mineral, which can be studied under a polarizing microscope. These properties, known

as optical properties, help in more precise identifications of even minute grains of

minerals. This helps in the identification of rocks, which are just nothing but aggregates

of different minerals.

How to prepare a Rock Slice

A thin section of the given mineral called the slide/Slice has to be first of all, prepared,

before it can be tested under a polarizing microscope.

Equipment:

1. Grinding wheels

2. Glass or steel plates

3. Abrasive powders (commonly Carborundum powders) of various course and fine

grades

4. Hot plates

5. Canada balsam

6. Glass strips

7. The cover slips

8. Methylated Spirit

Procedures

A chip of rock (or slice cut by a rotating steel disc armed with diamond dust) is

smoothed on one side and mounted on a strip of glass 75 x 25mm.

The specimen is cemented to the glass strip by means of Canada balsam, a gum

which sets hard after being heated, or a synthetic resin.

The mounted chip of rock is then ground down with Carborundum and emery

abrasives to the required thinners, general 30µm (1 micrometer =

1/1000millimeter)


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The transparent slice is completed by covering it with a thin glass strip fixed with

balsam.

Surplus balsam is washed off with methylated spirit. The surface of the specimen

has been smoothed in making the slice/slide, and they are free from all but very

small irregularities.

Note: At this stage, the specimen is ready for being studied under the Microscope.

Instruments and processes involved in optical mineralogy.

A polarizing microscope, also called a Petrological Microscope, is the most important

instrument which is used in any study dealing with the process of determining the

optical properties of minerals.

A polarizing microscope essentially consists of:-

a) a Reflecting mirror at the base,

b) A Nicol prism (called the polarizer) between the mirror and the stage;


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c) An objective above the stage

d) Another Nicol prism called the (analyzer) above the objective.

e) An eye- piece

The eye-piece, the analyzer and the objective are fitted into an adjustable tube, which

can be raised or lowered with the help of coarse (focusing) and fine adjustment

screws.

The polarizer also be raised or lowered with the help of its own adjuster

Such a Polarizing/ Petrological microscope is used to study the optical properties of

the given mineral.

The prepared slide of the sample is now placed on the stage of the microscope, and

studied for its optical properties.

The main optical characteristics are studied using polarized light and these include

Refractive index, Pleochroism, Extinction, Interference colours and Opaque

minerals.

Besides studying the main optical characteristics, the slide can be used to study some

general physical properties like colour, cleavage, shape, form, e.t.c of the minute

grains of the mineral, under the microscope, using ordinary light and without using

the polarizer and analyzer.

3.3.3 Chemical Properties of Minerals

3.3.3.1 Rock forming Minerals

The minerals which constitute the bulk of the rocks of the earth’s crust are called the

rock forming minerals.

Civil engineers are more concerned with the rock forming minerals because they need to

know the properties of the rocks precisely, to enable them to consider different rocks for

their civil engineering uses, like: picking the rocks as good foundations, or for using the

rocks for making concrete aggregates, as building stones, or road metal, or flooring,

roofing, or decorative materials, etc. Since the properties of rocks will mainly depend

upon the properties of their constituent minerals, a detailed study of the rocks forming

minerals becomes imperative for all the civil Engineers. The study of the minerals,

constituting a rock, will help him/her to identify the rock with reference to their

appearance, strength, durability, etc.


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3.3.3.2 Classification of Minerals

Minerals can be classified as:-

a) Silicate Minerals

b) Non-Silicate Minerals

c) Clay Minerals

A) Silicate Minerals

The existence of a silicon tetrahedron makes a mineral as silicate mineral.

1. Felspar/ Feldspar group

Felspars are the most abundant silicate mineral, in which the silicate tetrahedrons are

arranged in a three dimensional frame work, e.g feldspars and Quartz.

Types

i) Felspars

These are identified by their hardness (6.0), 2 cleavages at nearly right angles (85o to

86o) Gs 2.76 and light colours (such as white, pink, grey, etc). They are the most

important constituents of igneous rocks. Examples include:-

Plagioclase felspars, also called sodic felspars or soda lime felspars;

Potassium felspars also called potash felspars or orthoclase felspars.

ii) Quartz (Silca or silicon- dioxide SiO2)

Pure Quartz is white, but due to impurities it may have any colour, such as black, pink,

yellow, e.tc.

Its other characteristics are:- Vitreous luster, no streak, no cleavages, hardness = 7.0,

specific gravity = 2.65, and conchoidal fracture. Under microscope, Quartz grains are

found to have low refractive index and positive optical sign. Quartz occurs in a number

of varieties, such as low quartz, high Quartz, Tridymite, and cristobalite, chalcedony,

Agate and Jasper.

2. Pyroxene group or pyroxenes.

Pyroxene is a silicate mineral’s family, in which the tetrahedrons are arranged in single

chains that are held together by other positive ions, such as calcium, Magnesium and

Iron. Pyroxenes can be represented by the chemical formula: RSiO3, where R represents


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Ca, Mg, Fe, etc. They are generally recognized by dark colours, hardness (5-6), and 2

cleavages that meet at nearly right angles (93o or so)

Types

a) Orthorhombic pyroxenes, which include

- Enstatite (Mg. SiO3)

- Hypersthene (Fe.Mg.SiO3)

b) Monoclinic pyroxenes, which include

- Clino- enstatite (Mg.SiO3)

- Diopside- Hedenbergite (Ca, Mg (SiO3)2) and (CaFe (SiO3)2);

- Augite, a complex silicate (Mg, FeII, FeIII, Al) (Si Al) 2 O6)

- Aemite (NaFe (SiO3)2)

- Spodumene (LiAl (SiO3)2)

- Jadeite (NaAl(SiO3)2); e.t.c

c) Tricline pyroxenes; which include

- Rhodonite (MnSiO3) and Babingtonite.

Augite

It is characterized by: black - dark green colour, vitreous luster, no streak, two

directional distinct prismatic cleavages at an angle of about 90o, Gs = 3.2 -3.5, hardness

= 5.0 to 6.0. Its main use is its occurrence as an important rock forming mineral, which

occurs in many basic igneous rocks, and also in metamorphic rocks like Gneisses and

Granulites. A few lustrous varieties of Augite are used as gem stones.

3. Amphibole group or Amphiboles

In this group, the silica tetrahedrons are arranged in double chains. Amphiboles exhibit

cleavage in two directions at an angle of about 120o.

Examples

a) Orthohombic Amphiboles, which include: - Anthopyllite (CMg.Fe) SiO3), etc.

b) Monoclinic. Amphibole which include:

Cummingtonite Grunerite (Fe, Mg, Silicate)

Tremolite (Ca, Mg3(SiO3)4),

Hornblende (Ca2Na(Mg FeII)4 (AlFeIIITi)(Alsi)8 022(O,OH)2)


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Actinolite (Ca(Mg, Fe3) (SiO3)4)

Glaucophane (Fa, Fe, Al, Silicate)

Riebeckite (Na, Fe, Silicate)

c) Triclinic Amphiboles, which include: Aenigmatite

Hornblende It is characterized by: black, dark-green colour, vitreous luster, no streak,

2 directional distinct cleavages at an angle of about 120o, Gs = 2.9 to 3.4, hardness = 5

to 6.

Hornblende occurs mainly in acidic igneous rocks, and is used in the manufacture of

cement.

4. Mica Group or Micas

Micas are complex hydrous silicates of metals like potassium (K), Magnesium (Mg), iron

(Fe), etc. In all Micas, the silica tetrahedrons are arranged in sheets or layers thus giving

a clear cut sheet like formation or structure to these minerals. Due to this type of

structure, Micas will cleave, separating into thin flexible layers. E.g. Chlorite,

Serpentine, Talc, Biotite, Muscovite or Potas Micas

Examples

a) Biotite, Biotite is the name given to black Mica, and is represented by the chemical

formula (K(Mg Fe)3 (AlSi3 O10 (OH)2)

It is characterized by deep brown to black colour, vitreous pearly luster, no streak,

hardness = 2.5 to 3, sheet structure, perfect cleavage with the capability to split into

exceedingly thin sheets in one direction.

Gs. = 2.8 to 3.0, no fracture e.t.c

Biotite is found in many igneous rocks and metamorphic rocks. It is used in light weight

concrete.

b) Muscovite or Potas Micas

Muscovite is the name given to white mica and is represented by the chemical formula

(KAl2 (AlSi3O10) (OH) 2).

It is characterized by white colour, vitreous to pearly luster, no streak, hardness = 2 to

2.5, sheet structure, perfect cleavage with the capability to split into exceedingly thin

sheets in one direction, Gs = 2.7 to 2.9, even fracture e.t.c


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Muscovite usually occurs in igneous rocks like in Granites and pegmatite, and also in

metamorphic rocks like schist. Many sedimentary rocks also contain muscovite.

Muscovite is used as an insulating material in electrical instruments.

B) Non- Silicate minerals

These are minerals that do not contain silica tetrahedrons.

Important Non- Silicate Minerals

No Chemical group General Name Chemical Name Chemical Formula

1 Oxides Hematite Iron oxide (ferrous) Fe2O3

Magnetite Iron oxide (Ferric) Fe3O4

Liminite Hydrous Iron oxide Fe2O3 A H2C

Chromite Oxide of iron and chromium Fe.Cr2 O4

Corundum Aluminium oxide Al2O3

Bauxite Hydrated Alminium oxide Al2O3.2H2O

2 Carbonates Calcite Calcium carbonate CaCo3

Dolmite Calcium Mg. carbonate Ca,Mg (Co3)2

3 Sulphides Pyrite Iron sulphide FeS2

Chalcopyrite Copper iron sulphide CuFes2

Cinnabar Mercury sulphide Hgs

Galena Lead sulphide Pbs

Sphalerite Zinc sulphide Zns

4 Haloids Halite Sodium chloride Nacl

Fluorite Calcium fluoride CaF2

5 Sulphates Brite Barium sulphate BaSo4

Gypsum Calcium sulphate (hydrous) CaSo4.2H2o

Anhdrite Calcium

sulphate(anhydrous)

CaSo4


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C) Clay minerals:

These have properties that are of great importance to Geotechnical Engineers, Some

clays swell when wet and shrink when dry. Such clays can cause settlement in

foundation of structures and roads. Gs of clay = 2.60 to 2.90. Most of clay minerals

are soft and exhibit plasticity when mixed with a limited quantity of water. Particle sizes

(<0.002mm).e.g. – Kaolinite, Halloysite (amorphous), Montmorillonite, Beidellite,

Pyrophyllite, Allophane, Illite (hydro mica), chlorite, Bentonite clay, china clay (Kaoline),

Ball clay

Kaolinite

Kaolinite is a clay mineral used as a raw material in the manufacture of pottery and

porcelain, filler in rubber, paint and paper industry.


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CHAPTER FOUR

Matthew 16:18

Jesus Christ said “Now I say to you that you are Peter (which means ‘Rock’), and upon this Rock I will build my church, and all the powers of

hell will not conquer it.

4.0 PETROLOGY

4.1 Definitions

The term petrology is derived from the Greek word, Petro +Logos. Petro means rocks

and logos mean study. Hence, petrology means the study of the rocks.

Petrology deals with the study of mode of formation, structure, texture, composition,

occurrence, types, and e.tc of the various rocks of the Earth’s crust.

Rocks are the aggregates of minerals, including hard as well as soft materials, like

stones, sands, clay, e.t.c

4.2 Rock Cycle

The rocks of the Earth’s crust are of 3 types;-

- Igneous rocks

- Sedimentary rocks

- Metamorphic rocks

The Igneous rocks are prime most rocks which solidify from a molten mass, called

magma. These rocks are formed below the Earth’s surface as well as on the Earth’s

Definitions

Rock Cycle

Types of Rocks

Igneous Rocks

Sedimentary Rocks

Metamorphic Rocks

SUMMAR


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surface. The ones formed below may be exposed by their continued erosion caused by

water, oxygen, carbon dioxide and temperature changes. These rocks are attacked and

disintegrated by these external agents of weathering (the collective process of rocks

disintegration and decays). When these rocks have been weathered into loose material,

they are subjected to removal by wind, water, ice, or organisms. After moving some

distance, these loose sediments may again come to rest, and thus get deposited over

other rocks in layers, forming what are called as the sedimentary rocks/ stratified rocks.

Once having formed from a molten mass (i.e Igneous rocks) or through the process of

sedimentation or stratification (i.e. sedimentary rocks), a new environment of heat,

pressure or both generally in the presence of hot fluids such as water, may be imposed

upon these rocks and thereby changing them into a third type of rocks, called the

metamorphic rocks.

These metamorphic rocks can be further subjected to over powering stresses and heat,

which may cause the melting of metamorphic rocks, giving rise to new igneous rocks.

The sequence of events, described above, constitutes what is known as the rocks cycle.


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4.3 Types of Rocks

As mentioned earlier, there are three types of rocks namely:-

a) Igneous rocks

b) Sedimentary rocks

c) Metamorphic rocks

4.3.1 Igneous Rocks (Eruptive Rocks)

4.3.1.1 Formation of Igneous Rocks

Igneous rocks or eruptive rocks are formed when magma (natural hot molten material or

liquid rock, probably existing below the Earth’s surface) erupts out on or within the

Earth’s surface due to volcanic activities.


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4.3.1.2 Mode of occurrence of Igneous Rocks

Igneous rocks may occur in two ways, either as intrusive bodies (i.e. large rock masses

which have not formed in contact with the atmosphere), or as extrusive bodies (i.e. those

rocks which occur above the surface of the Earth).

These intrusive and extrusive bodies may occur in different forms depending upon

factors, such as, the capability and strength of Magma; the type, texture and strength of

adjoining rocks, etc. The various forms in which these intrusive and extrusive igneous

rocks may occur are explained below.

4.3.1.3 Forms of Intrusive Rocks (Plutonic Rocks)

Intrusive rocks occur when magma is unable to disturb and cut across the existing

intruded rocks, it may get cooled and solidified within the fissures and cavities prevailing

in the existing rocks. Intrusive rocks may occur in different forms, such as: - Sills,

Phacoliths, laccoliths, Dykes, Batholiths and volcanic neck.

1. Sill.

Occurs when the magma is pushed into the existing bedding layers of the intruded rocks;

and solidifies there, in the form of a thin sheet.

Rock A

Sill

Rock B

2. Laccoliths.

Occurs when magma injects into the layers of the intruded rocks, but is unable to spread

length and width wise for greater distances due to high viscosity, it may force the layers

of rocks upwards, in the form of a dome or an arch.

Intruded rocks arching up

Laccoliths


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3. Dykes.

Occurs when the magma is forced through the vertical or nearly vertical cracks or

fissures in the intruded rocks and is consolidated there as a wall like structure.

Dyke

Rock A

Rock B

Rock C

4. Batholiths.

This occurs when the magma moving under high pressure fills up a large space in the

pre-existing intruded rocks by melting them away or keeping them aside, or by any other

means; thus forming a huge mass of igneous rock.

Rock A

Rock B

Rock C

Batholiths

4.3.1.4 Forms of Extrusive Rocks (Volcanic Rocks)

These are igneous rocks that crystallize on the surface of the earth. The magma is poured

out at the surface. They undergo rapid cooling such that there is no enough time to form

large crystals. Their texture is glass like.

They occur in two major forms:-

1. Flow or Lava flows


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Flows are identical to sills in their external appearance, because when lava oozes out, it

will spread over the surface in thin sheets, getting consolidated there.

2. Pyroclastics.

These are all associated with volcanism and represent rock fragments blown out of

volcanoes during eruptions.

They are classified according to size and include:-

Volcanic bombs (include materials from a few centimeters to meters in diameter)

Cinders (include materials from 5mm to several centimeters in diameter)

Tuffs (include materials less than 5mm in diameter)

Volcanic ash (is the finest dust particles which remain suspended in the atmosphere

for months together before settling down on the earth).

4.3.1.5 Classification of Igneous Rocks

1. Plutonic rocks. Intrusive igneous rocks formed at great depth

a) Granites, b) Syenites, c) Gabbros d) Peridotities, e) Diorites

2. Hypabyssal rocks: are intrusive igneous rocks formed below the surface of the earth

but at a short distance, e.g. Dolerites

3. Volcanic rocks: - These are extrusive igneous rocks formed over the earth’s surface

a) Rhyolites b) Andesites c) Basalts

Granites

Granites are light coloured rocks of plutonic origin. Their colours are grey, pink or red

and depend chiefly upon the colour of the feldspar mineral present in a particular

Granite. They are acidic in nature, with Quartz and feldspar as essential minerals.

Texture: Granites are generally of coarse-grained texture and sometimes of medium-

grained textures.

Types: Granites are named after prominent presence of a particular accessory mineral

like Hornblende Granite, Biotite Granite, Tourmaline Granite, Augite Granite, Muscovite

Granite e.t.c

Mode of occurrence: Granites commonly occur in the form of large igneous bodies, like

batholiths. May also occur in the form of large igneous bodies, like batholiths; also may

occur in the form of dykes.


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Physical properties and uses: They have a very high crushing strength (100 to

250MN/M2); low water absorption value (0.5-1.2%); least porosity (very low); Specific

gravity (2.6 to 2.8); Density (2500 to 2650Kg/m3); Hardness (very hard with Hardness

coefficient as 18); Frost and fire resistance (Good frost resistance but low fire resistance).

Granites are extensively used as building stones for structural as well as decorative,

monumental and architectural purposes. They can take fine polish and are the strongest

available stones. They can also be used as road aggregates and concrete aggregates.

Dolerites

These are hypabyssal igneous rocks, dark (such as grey or black) in colour. They chiefly

consist of calcic plagioclase felspars, such as, Labradorite and Anorthite. The

ferromagnesian minerals generally present are olivine, Augite and iron oxides.

Textures: Dolerites have fine-grained texture.

Mode of occurrence: Dolerites commonly occur as sills and dykes.

Properties and uses: They are highly tough and possess high abrasion resistance. They

are not used as building stones but are generally used as crushed stones for concrete

aggregates and for making road.

Andesites

They are light coloured volcanic rocks. The essential minerals are felspars.

Texture: They are generally fine-grained aphanitic rocks.

Types: These include. Hornblende Andesite and Biotite Andesite base on the presence

of prominent quantities of accessory minerals, such as Hornblende & Biotite.

Mode of occurrence: They are the most abundant volcanic rocks, but next to Basalts.

They occur in the form of lava flows of huge dimensions.

Properties and uses: Like all volcanic rocks, they are not of much use as dimension

stones. They may be used as crushed stones.

4.3.2 Sedimentary Rocks/Stratified/Secondary Rocks

It is called Stratified rock because sediments are deposited and consolidated in layers.

It is called Secondary rock because it is formed from some existing primary rocks.


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Sedimentary rocks are formed by the deposition and consolidation of new sediments

(loose or solid particles), in layers, over the pre-existing rocks. The sediments are eroded

away from some old rocks by weathering and are then transported by agents like wind,

water, ice, etc. The eroded sediments, after traveling, may get deposited over some

existing rocks, which on consolidation will form sedimentary rocks. About 75% of the

rocks on earth’s surface are sedimentary in origin.

4.3.2.1 Formation of Sedimentary Rocks

The sedimentary rocks are formed in the following four different stages:-

i) Weathering (i.e. erosion of the existing rocks)

Mechanical weathering disintegrates a pre-existing rocks into smaller fragments and

chemical weathering acting on these small fragment, rearranges the elements into new

minerals and thus decomposes them.

ii) Transportation of Eroded sediment.

The products of rock weathering are generally transported in large amount by the

running waters (i.e. rivers), moving ice (i.e. glaciers), and blowing winds.

iii) Deposition of Eroded Sediment

The transportation of the weathered products continues as long as the velocity of the

transport of medium remains unchecked. But when these products are brought at rest

into big water bodies like oceans and lakes, their deposition will start. Of the weathered

products carried in suspension, the coarser and the heavier pieces will settle first,

followed by lighter and finer particles. The weathered products carried in solution may

precipitate out at a later stage, which may form a separate layer on deposition.

iv) Lithification of Deposited sediment.

The transformation of loosely deposited sediments into a rock is called lithification. This

can be done in 2 ways:-

a) By compaction or consolidation: As deposition of sediment continues, it

automatically goes on compacting and consolidating due to its own weight with

the squeezing out of water.


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b) By cementation: Water soluble materials, such as calcite, silica, iron oxides,

dolomites, clay, e.t.c; are deposited by ground water, between the various grains

of the deposited sediment thus bonding them together.

4.3.2.2 Classification of Sedimentary Rocks

Sedimentary rocks can be divided into three categories i.e.

1. Clastic rocks

The word clastic means fragmental. Clastic rocks are derived from fragments or

individual minerals of other rocks. E.g. Breccias, conglomerates, sandstones, shale,

Boulders, cobbles, Pebbles or coarse gravel, Gravel or Granules, sand (coarse and fine),

silt and clay.

2. Chemical sediments/Chemically formed sedimentary rocks

These are rocks formed when weathered materials which travel in solution and reach the

water bodies such as lakes and oceans get precipitated. E.g. limestone, -

Dolostone/Dolomite, Rock gypsum and rock salt

3. Organic Sediments and organic Sedimentary rocks

Organic sediments are derived from the biological activities of various organisms, living

in water bodies, which consume the weathered products in solution and sediments. The

remains of dead organisms also keep on accumulating and consolidating, resulting in

the formation of organic rocks e.g. coal, coprolites and guano e.g. organic lime stone.

Size of Clastic Sediments

Name of the particle Size or Diameter in mm

Boulders 300 and above

Cobbles 80 to 300

Pebbles or coarse gravel 20 to 80

Gravels or Granules 4.75 to 20

Sand (coarse and fine) 0.075 to 4.75

Silt 0.002 to 0.075

Clay <0.002

Sand stones


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Sandstones are clastic sedimentary rocks, formed by Lithification of sand beds of size

2mm to 0.1mm. Quartz is the chief mineral constituent.

Texture: Sand stones may be of coarse and fine grained types.

Types: are based on the type of cementary materials e.g. Siliceons sandstones;

Calcareous Sandstones; Argillaceous Sandstones; Ferruginous Sandstones.

Occurrence: They occur in thick or thin beds and sometimes as lenticular bodies within

the beds of other rocks.

Uses: As building stones; those with high silica and low iron are used in glass

manufacture; crushed sandstones of many types are used for road construction and as

rail-road ballast.

Shales

These are clastic sedimentary rocks formed by clay particles of less than 0.01mm in size.

Depending on the clay minerals and impurities present in the rock, shales are of colours

like grey, red, purple, green black etc. They are soft and brittle rocks, which crumble

easily under the hammer.

Types: Depending upon their composition, include: calcareous shales; siliceous or

sandy shales; carbonaceous or bituminous shales; Alum shales; and oil shales.

Occurrence: They occur as thin and thick beds and sometimes as small bands and

irregular inclusions within other sedimentary rock formations.

Uses: Because of their thin-bedded structures, sometimes cause trouble in tunneling, as

the material may dislodge quite easily. They may also give trouble in dam foundations.

Shales are also not as hard as sandstones and if unsupported, they may yield to the

pressure of the overlying rocks. They are of no value as building stones. But, they are

used in the manufacture of clay products, such as, bricks, tiles, sewer pipes; and

Portland cement.

Conglomerates

These are clastic sedimentary rocks, with the constituent fragments of more than 2mm

in size they consist of rounded pebbles, gravels, boulders e.t.c cemented together.

Types: Volcanic conglomerates; Basal Volcanic conglomerates; Glacial conglomerates;

Gravel conglomerates (fragment size = 4.75 to 20mm); Pebble conglomerates (fragment


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size = 20 to 80mm); cobble conglomerates (size = 80 to 300mm) and Boulder

conglomerates (size>300mm).

Uses: Because of their coarseness, are of little values as building stones. The harder and

denser types may be used as milestone (landmark, sign post, target); also crushed stones

for roads, making concretes, as rail-road ballast.

Lime stone

These are sedimentary rocks formed by chemical as well as organic processes.

Type: chalk, argillaceous limestone, Shelley limestone, Kankar limestone, Calc-Tuffa,

lithographic limestone, siliceous limestone.

Uses: Used as crushed stones for road making, for concrete aggregates, used as internal

and external building stones- chief ingredient in the manufacture of cement, glass

manufacture, sugar refining, used in the manufacture of Rock wool/Mineral wool

(insulation material: a lightweight fibrous material made from slag or glass. Use:

insulation, packing material, filters); etc.

Coal

This is a combustible organic rock composed primarily of carbon, hydrogen, and oxygen.

Coal is burned to produce energy and is used to manufacture steel. It is also an important

source of chemicals used to make medicine, fertilizers, pesticides, and other products.

4.3.3 Metamorphic Rocks

Metamorphic rocks (from the Greek word “Meta”, meaning between, also denoting change

and “Morphe” means form or shape) are rocks changed in same way from either an

original igneous or sedimentary form.

The new rocks which are formed from the alteration of the pre-existing rocks of any type,

by the process of metamorphism, are called metamorphic rocks.

Metamorphism is defined as a process or phenomenon by which the existing rocks are

modified texturally, structurally and mineralogically under the influence of factors, such

as, heat, pressure and hot chemically active fluids, such as water.

The Igneous and sedimentary rocks, when subjected to metamorphism, undergo changes

that are physical, chemical or both. Physical changes are reflected as changes produced


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in the texture of the old rocks, whereas chemical changes produce the formation of new

minerals, thus, giving rise to this new group of rocks, called metamorphic rocks.

4.3.3.1 Classification of Metamorphic Rocks

List of sedimentary rocks and their corresponding metamorphic rocks

Sedimentary rock Metamorphic conversion

Conglomerate Gneiss and schist

Sandstone Quartzite

Shale Slate, phyallite and schist

Limestone Marble and schist.

List of igneous rocks with their corresponding metamorphic conversion rocks

Igneous Metamorphic conversion

Coarse- grained rocks, such as Granite, syenites, e.t.c Gneiss

Fine-grained rocks, such as felsites, Tuffs, e.tc Schists, slates, etc

Ferromagnesian rocks, such as Dolorites, Basalts, Shists, e.t.c

4.3.3.2 Important metamorphic rocks

1. Gneisses

2. Schists

3. Phyallite

4. Slates

5. Quartzites

6. Marbles

7. Miscellaneous rocks, like:

Hornfels, soapstone, serpentine

Gneisses

This is any banded or layered metamorphic rock, whether originally of igneous (Granite,

syenite, e.t.c) or sedimentary (conglomerate) origin.

Foliated Rocks: are rocks when secondary structures in the

form of parallel arrangement of minerals in layers, are

developed during metamorphism.

Non-Foliated Rocks


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Types: Biotite Gneisses; Hornblende Gneisses; Granite Gneisses; Otho- Gneisses; Para-

Gneisses; Banded Gneisses; Augen Gneisses.

Colours: vary from white to black.

Uses: Because of their banded structure, Gneisses cannot be worked so uniformly as

Granites and hence their use is more restricted. On the other hand, their banded

structures permit their easy splitting into more or less parallel flat surfaces and thus

promoting their easy use in construction of rough walls and in street works. Granite

gneisses are most widely used for structural works, as they are similar to Granites in

respect of their specific gravity, water absorption and crushing strength. Gneisses may

also be used for concrete and road aggregates.

Slate

Slate is an extremely fine-grained textured metamorphic rock, formed by the

metamorphism of shale (a sedimentary rock).

Types: Black slates (common slates), Grey slates, Green slates, purple slates.

Uses: Slates are rather soft rocks, which can be easily cut into sheets and pieces. They

are, thus, widely used in electrical industries as switch boards, bases and various turned

and shaped parts. In construction of buildings, slates are also used for floors, mantels

(fireplace frame: an ornamental frame around a fireplace usually made of stone or wood)

and in a variety of ways; slates are also used as roofing materials. They are, however,

not used as dimension stones or as crushed stone, because of the low crushing strength

and slaty cleavage.

Marbles

Marbles are calcareous, compact crystalline granular rocks, formed by the

Metamorphism of limestone generally and Dolostones occasionally.

Types: Calcite marble and Dolostone marble. Marbles, though white when pure, yet due

to the presence of mineral impurities, are usually found to have various beautiful

colours, such as black, grey, red, pink, brown, green, yellow, e.t.c

Uses: Marbles are extensively used as building stones, especially for ornamental and

decorative purposes in columns, pilasters, staircases, floors, etc. They may also be used

for building monumental or architectural buildings, statues, e.t.c


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CHAPTER FIVE

Africa must refuse to be humiliated, exploited, and pushed around. And with the same determination, we must refuse to

humiliate, exploit or push others around.

Julius Kambarage Nyeree (1922 - 1999), Tanzanian President

5.0 STRUCTURAL GEOLOGY

5.1 Definitions

Structural Geology can be defined as the branch of geology concerned with the shapes,

arrangement and interrelationships of bed rock units and the forces that cause them.

In the study of structural Geology, the following are the major concerned:

1. The force acting on the rock

2. The response of the rock

3. The geometrical features of the rock.

Due to a force acting on a rock it may undergo deformation.

The major terms considered under deformation are:-

Stress: This is a force acting on a body, or rock unit that tends to change the size or

shape of that body, or rock unit. Force per unit area within a body. Stress brings about

permanent deformation if the strength of the body is exceeded.

Definitions

Folds

Fractures in Rock

Joints

Faults

SUMMAR


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Strain: Change in size (volume) or shape of a body (or rock unit) in response to stress.

Strain is the result of the application of the stress. The stress that causes the deformation

of a rock is not present any more but the strain is; and so we can work backwards to

determine the stress. The strain tells you the kind of force that acted on bedrock.

Ductile deformation

A rock that behaves in a ductile or plastic manner will bend while under stress and does

not return to its original shape after relaxation of the stress.

Ductile behavior results in rocks that are permanently deformed mainly by folding or

bending of rock layer.

Brittle deformation

Rocks exhibiting brittle behavior will fractural/break at stresses higher than its elastic

limit.

Faults and joints are examples of structures that are formed by brittle behavior of the

crust.

5.2 Folds

Folds are bends or undulations or wavelike features in layered rocks of the Earth’s crust,

as a result of the stresses (commonly lateral compression) to which these rocks have

been subjected to, from time to time in the past history of the Earth.

Folded rocks can be compared to several layers of rugs or blankets that have been pushed

into a series of arches and troughs.

The fact that rock is folded shows that it was strained in a ductile way rather than by

elastic or brittle strain.

5.2.1 Causes of Folding

Folding of rocks may be caused by numerous factors or causes, which may be divided

into two main types:

1. Tectonic causes. These are causes which are produced due to the forces operating

within the Earth’s crust, such as lateral compression caused by shrinkage;


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2. None-Tectonic causes of folding. These include all those rock folding effects which

are effective over the ground surface, resulting, mainly under the influence of

gravitational force, such as

a) Land sliding

b) Creeping (a gradual movement of rock and debris down a slope/ a slow

deformation of rocks and minerals in response to prolonged stress).

c) Differential compaction

d) Isostatic settling

e) Subsidence into solution cavities and glaciations

5.2.2 Parts of a fold and connected terminology

The various parts of a fold and the terms generally used in describing them are explained

below with respect to the vertical cross-sections of the folds or the folded area.

Limbs: Limbs are the sides of a fold.

An individual fold will have two limbs. Each anticline and adjacent syncline shares a

limb (common central limb).


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Crest: Crest is the line running through the highest points in an up-arched fold.

Trough: Trough is the line running though the lowest points in a down-arched fold.

Anticline: Is when the beds are up folded into an arch-like structure. In such folds,

the beds on either sides are inclined away from the crest and that is why the name

anti-cline.

Syncline: Is when the beds are down folded into a trough like form. In this case the

bends on either side incline together towards the keel.

Axial plane: This is the imaginary plane bisecting between the two limbs of a folder,

thus dividing the fold into two parts, as symmetrically as possible.

Axis of the fold: The line of intersection of the axial plane with any bed of the fold

is termed as the plunge or pitch of the fold. When the fold axis is inclined, the angle

which it makes with the horizontal, as measured in a vertical plane, is called the

angle of plunge, or plunge of the fold. Such folds with inclined fold are known as

plunging folds or pitching folds.

5.2.3 Types of Folds

1. Open folds

Open folds have limbs that dip gently. All other factors being equal, the more open the

fold, the less intense the stress involved.

The two diagrams show alternate ways that stresses may have been distributed to have

caused the folding.


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2. Isoclined fold.

Isoclined fold is one in which limbs are parallel to one another, implies intense

compression.

3. Recumbent folds.

These folds are overturned to such an extent that the limbs are essentially horizontal.

Recumbent folds are found in the cores of mountain ranges and indicate compressive

and/or shear stresses were more intense in one direction and probably record

shortening of the crust associated with plate convergence.


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4. Overturned fold.

Overturned fold occurs where the axial plane is inclined to such a degree that the fold

limbs dip in the same direction. Overturned folds imply that unequal compressive

stresses or even a shearing stress caused the upper limb of the fold to override the lower

limb.

5. Other types.

a) Upright folds: These are folds that have vertical axial planes.

b) Asymmetric fold: Is a fold where the axial plane of a fold is not vertical but is

inclined.

5.2.4 Engineering Considerations involved in Dealing with Folded Rocks

A civil engineer has to be very cautious, while s/he is handling or excavating through

the folded rocks, because whenever, the folds are disturbed, they release the stored

energy and may damage the site in various ways. Moreover, folded rocks are generally

highly fractured, particularly along the axial parts. These fractures, not only make the


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rock weak, but also act as channel-ways for the surface waters to percolate through

them. All major projects, like construction of highways, construction of tunnels, site

selection for dams and reservoirs, etc. due consideration must be given to the presence

of folds. The following are the various effects produced by folded rocks:-

1) Synclinal folded rocks may yield hard and tough quality stones, whereas, anticlinal

folded rocks will yield weaker stones.

2) Folded rocks are under considerable strain, and hence, excavations through them

may be accompanied by slips and rock bursts.

3) Folded rocks are generally shattered and weak, particularly in the axial regions;

hence, they are unsafe to be trusted as roofs or floors of tunnels, or as foundations

for dams. Such regions should therefore, be avoided for such purposes, or must be

thoroughly investigated, and remedial measures taken, if at all adopted for such uses.

4) Fractured folded rocks are highly permeable, and as such may pose numerous

problems; like, while excavating tunnels through such regions, ground water may

rush into the excavation.

5) Since the folded rocks offer greater prospects for groundwater, they become quite

important for engineers searching for water supplies. Artesian conditions are

developed only when aquifers are folded (or inclined) as synclines, and are enclosed

between top and bottom impervious layers.

6) The anticlinal folds provide good prospects for stored petroleum; and hence in oil

exploration, folds must not be overlooked.

5.3 Fractures in Rock

If a rock is brittle, or if the strain rate is too rapid for deformation to be accommodated

by plastic behavior, the rock fractures or breaks. Commonly there is some movement or

displacement. If essentially no displacement occurs, a fracture or crack in bedrock is

called a joint. If the rock on either side of a fracture moves, the fracture is a fault.


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5.3.1 Joints

Joints are fractures or cracks in bedrock along which essentially no displacement has

occurred. These joints, divide the rock into parts or blocks, but these blocks are not

moved past each other as in the case of fault.

The inclination of a joint plane with the horizontal is called the dip of the joint. The line

along which the joint plane meets the surface is called the strike of the joint, the strike

direction being perpendicular to the dip direction.

Dip joint

Strike joint Oblique joint

Sheets

Joint Bedrock

5.3.1.1 Examples of joints

1. Strike joints: These are joints in which the strike of the joints is parallel to the strike

of the bed.

2. Dip joints: These are joints in which the strike of the joints is perpendicular to the

strike of the beds (i.e. parallel to the dip of the beds)

3. Oblique joints: These are joints in which the strike of the joints is neither parallel

nor normal to the strike of the bends

4. Sheet joints: These are horizontal joints developed in massive igneous rocks,

especially granite. They divide the rocks into sheets. These horizontal joints are

closely spaced in the upper layers and become progressively further a part with depth.

5. Shear joints: These are joints formed by the shearing stresses, which tend to slide

(or actually slide) one part of the rock against the other. These joints are developed

during folding or faulting


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5.3.1.2 Engineering Considerations involved in Dealing with Jointed

Rocks

For construction of any major civil engineering structure in any area, it is absolutely

necessary to investigate the rock joints thoroughly, mainly because joints act as sources

of weakness for the rocks, and also sources of leakage through the rocks.

Hence, if the proposed foundation rocks for a dam or a reservoir happen to be heavily

jointed, and if the water-table of the region is low, then the leakage from the reservoir to

the underground may be very heavy, finally resulting in abandoning the proposed site,

and to choose better one. Similarly, in construction of tunnels, if the roof or the side

rocks are highly fractured or jointed, the groundwater may seep into the tunnel, thus

creating acute water troubles, in addition to its becoming unstable or unsafe structurally.

The joints in rocks play a very important role in landslide in hilly regions, because they

serve as slip surfaces.

The effects of joints on the proposed structure should, therefore, be thoroughly

considered and remedial measures undertaken, before the actual construction of the

structure. Treatment of joints will differ in different projects. E.g. when leakage is to be

avoided, grouting of joints is generally adopted. Similarly, when the jointed rocks offer

instability or unsafe, as in the case of heavily jointed roofs of tunnels, lining of tunnels

may become necessary.

In addition to all these engineering problems, study of joints becomes important in

quarrying and mining operations. In quarrying of stones, joints may help in making

quarrying easier, if quarrying is done along them.

5.3.2 Faults

Fault is a rock fracture or a fracture surface along which relative movement between the

fractured parts occurs. The phenomenon of development of such fractures and

occurrence of the relative displacement of blocks is known as faulting.


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5.3.2.1 Fault terminology

1. Fault plane: This is the surface along which fracture occurs in the rock body and

there occurs a relative movement between the so formed rock parts.

2. Fault trace/outcrop/line: Is the line of intersection of a fault plane with the ground

surface.

3. Dip of the fault: Is the inclination of the fault plane, with the horizontal and its

represented in degrees.

4. Strike of the fault: is the direction perpendicular to the dip direction.

5. Hade: is the angle which the fault plane makes with the vertical. Hade = (90o – dip of

the fault).

6. Hanging wall and footwall: A fault plane separates the two blocks and each block is

known as a wall. If the fault plane is inclined, then the block lying over the fault


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plane is called the hanging wall, whereas, the block lying beneath, i.e. underside of

the fault plane is called the foot wall.

7. Up-throw side and down-throw side: Of the two blocks of a fault, the one which

moves up with respect to the other is called the up-throw side; and the one, which

moves down with respect to the other is called the down-throw side.

8. Throw: The throw of a fault, is the total vertical displacement in a fault

9. Heave: Is the total horizontal displacement in a fault (i.e., the horizontal distance

between hanging wall and foot wall).

10. Slip: Slip of a fault is the relative displacement of two points which were initially

against each other.

5.3.2.2 Types of Fault

Normal fault; thrust fault; Trans-current fault; tear/transverse fault; vertical fault; high

angle fault; low angle fault; strike fault; Dip fault; oblique fault; Dip-slip fault; strike-slip

fault; wrench fault; rift fault; oblique-slip fault; parallel fault; Echelon fault;-step fault;

peripheral fault.


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5.3.2.3 Engineering Considerations involved in Dealing with Faulted

Rocks

Faulted rocks generally offer unstable sites from engineering considerations, not only

because there have been displacements along the fault(s) in the past, but also that

further fresh movements may take place at any time in the future. Thus, if a structure

is constructed on such rocks, then any future movements along the faulted plane(s) may

endanger the stability of the structure, and thus causing it to collapse.

An engineer, as a general rule, must try to avoid locating any of the proposed structures

on fault or rather even in its vicinity.

When an engineer decides to put the proposed project in moderately faulted regions,

precautions must be taken to avoid any major failures, either by seismic effects caused

by movements along the faults, or due to heavy leakage that may take place through the

faulted rocks. The improvement works in faulted rocks, such as excavation of weaker

material from the faulted zone and refilling or grouting it with cement concrete, etc. may

therefore become necessary.


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CHAPTER SIX

Matthew 27:54

The Roman officer and the other soldiers at the crucifixion were terrified by the earth quake and all that had happened.

They said, “This man (Jesus Christ) truly was the Son of God!”

6.0 EARTH QUAKE

Definitions

Causes of Earthquakes and their types.

Seismic waves

Measuring of the size of an Earthquake

Effects of Earthquake

Tsunami

SUMMARY


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6.1 Definition

An Earthquake is a natural vibration of the ground (or the Earth’s Crust) produced

by forces called earth quake forces or seismic forces.

Or An Earthquake is a trembling or shaking of the ground caused by sudden release

of energy stored in the rocks beneath Earth’s surface.

6.2 Causes of Earthquakes and their types

Depending upon the possible cause of an earthquake, earthquakes are generally

classified into two categories i.e.

1) Tectonic earthquakes

2) Non-Tectonic earthquakes

a) Tectonic Earthquakes

Tectonic is the force that produces movement and deformation of the Earth’s crust. The

tectonic earthquakes are caused by the slippage or movement of the rock masses along


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a rupture or breaks called a fault. These are generally very severe and the area affected

is often very large. Faulting is a phenomenon which has been associated with most of

the severe earthquakes of the world. As such, it can generally be considered as the

immediate cause of many tectonic earthquakes.

b) Non-tectonic earthquakes

Non Tectonic earthquakes are earthquakes caused by a number of easily understandable

processes, such as; volcanic eruptions, superficial movements like landslides,

subsidence of the ground below the surface, etc. All such processes may introduce

vibrations into the ground.

6.3 Seismic waves

The energy released during faulting, produces seismic waves which can be detected by

sensitive and delicate instruments, called seismographs, installed at specially designed

seismographic stations; the record of seismic waves is called seismogram.

Epicenter

Epicentral line Focus

Earth surface

Solid earth

Anticentre

The focus or seismic center is the place beneath the Earth’s surface from where an

Earthquake originates and the point or line on the Earth’s surface immediately above

the focus is called the Epicentre or Epicentral line. The point which is diametrically

opposite to the epicenter is called anticentre. The area around the epicenter will be

subjected to earthquake vibrations, and is called epicentral area.

Earthquake foci are distributed in 3 general depth ranges. Shallow earthquakes

originate within about 60km of the surface; intermediate earthquakes have force


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between 60 to 300km down; and the deep seated earthquakes originate at depths

below 300km, or so.

6.4 Types of seismic waves

6.4.1 Body waves:

Body waves are seismic waves that travel through the Earth’s interior spreading

outwards from the focus in all directions, e.g.

a) P wave (primary): is a compressional (or longitudinal) wave in which rock vibrates

back and forth parallel to the directions of wave propagation. It’s very fast and the

first to arrive at a recording station following an Earthquake

b) S wave (secondary): These are waves that travel in directions at right angles (i.e.

transverse) to the directions of propagation of the wave. These waves travel slower

than the P-waves, and are second to be recorded at the seismographic station. The

velocity of S-wave is controlled by the resistance of a medium to shear. Due to this

reason, these waves, though capable of passing through solids, yet cannot pass

through liquids, as liquid do not have any distortorial elasticity.

6.4.2 Surface waves

These are the slowest waves, set off by earthquakes. Surface waves causes more

property damage than body waves because surface waves produce more movement

and travel more slowly, so they take longer to pass e.g.

a) Love waves: are most like S waves that have no vertical displacement. The ground

moves side to side in a horizontal plane that is perpendicular to the directions,

the wave is traveling or propagating. Like S waves, love waves do not travel

through liquids and would not be felt on a body of water. Because of the horizontal

movement, love waves tend to knock buildings off their foundations and destroy

highway and bridge supports.

b) Rayleigh waves: These behave like rolling ocean waves and cause the ground to

move in an elliptical path opposite to the direction of the wave passes. Rayleigh

waves are incredibly destructive to buildings because they produce more ground

movement and take longer to pass.


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c) d) Fingerprint of an Earthquake

e) A seismograph produced this record of a California earthquake measuring 5.5 on the Richter scale. The

finger points to a heavy sweep on the seismogram created by the seismograph’s needle, or stylus,

which is designed to respond to horizontal or vertical vibrations, but not both. The machine cannot

record both kinds of waves because the different orientation of the wave types requires separate

balance systems.

6.5 Measuring of the size of an Earthquake

The size of the Earthquake is measured into two ways:-

6.5.1 Intensity:

Intensity is a measure of an Earthquake’s effect on people and buildings. Or intensity

of an earthquake is the rating of an earthquake based on the actual effects produced

by the quake on the earth. Intensities are expressed as Roman numerals ranging from

l to Xll

6.5.2 Magnitude:

Magnitude is a measure of the energy released during an earthquake. This method is

usually done by measuring the height (amplitude) of one of the wiggles on a

seismogram. The larger the quake, the more the ground vibrates and the larger the

wiggle. After measuring a specific wave on a seismogram, and correcting for the type

of seismograph and for the difference from the quake, scientists can assign a number

called the magnitude.


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Intensity scale for Earthquakes with approximately corresponding magnitudes

Intensity

class

Maximum

Acceleration of

the ground in

mm/sec2

Name of the

shock

Effects observed Magnitude (M)

corresponding to highest

intensity reached

I. 10 Imperceptible Recorded only by sensitive seismograph

3.5 to 4.3

II. 25 Feeble Recorded by all seismographs and may

be felt by some sensitive persons at rest

III. 50 Slights Commonly felt by all people at rest,

especially on upper floors

4.3

IV. 100 Moderate Commonly felt by all people, either at

rest or in motion; knocking of loose

objects including standing vehicles

4.3 to 4.9

V. 250 Fairy strong Generally felt; most sleeping persons are

awakened; ringing of bells

VI. 500 Strong Trees sway and all suspended objects

swing; fall of weak plasters; general

panic; damage by overturning and falling

of loose objects.

4.9 to 5.5

VII. 1000 Very strong Damages to buildings producing cracks

in walls etc; fall of chimmeys; general

alarm & panic

5.5 to 6.2

VIII. 2500 Destructive Car drivers seriously disturbed; masonry

fissured; poorly constructed buildings

damaged.

6.2 to 7.0

IX. 5000 Ruinous Some houses collapse where ground

begins to crack; pipes break, opens.

X. 7500 Disastrous Ground cracks badly; many buildings

destroyed; railway lines bent; landslides

occur on steep slopes

7 to 7.3

XI. 9800 Very

disastrous

Few buildings remain standing; bridges

destroyed; and services like railways,

pipes, cables, etc. getting out of actions;

great landslides and floods.

7.4 to 8.1


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XII. Over 9800 Catastrophic Total destruction objects thrown into air

ground rises and falls with waves.

> 8.1 (maximum known

8.9)

6.6 Effects of earthquakes

Damage to buildings and other structures depends greatly on the type of geologic

material on which a structure was built as well as the type of construction. Houses built

on solid rock normally are damaged far less than houses built upon loose sediment.

Brick and stone houses usually suffer much greater damage than wooden houses, which

are somewhat flexible.

1. Ground motion is the trembling and shaking of the land that can cause buildings to

vibrate.

2. Fire is a particularly serious problem just after an earthquake because of broken gas

and water mains and fallen electrical wires.

3. Landslides can be triggered by the shaking of the ground.

4. Permanent displacement of the land surface may be the result of movement along a

fault.

5. Aftershocks are small earthquakes that follow the main shock. Although aftershocks

are smaller than the main quake, they can cause considerable damage, particularly

to structures previously weakened by the powerful main shock.

6. Foreshocks are small quakes that precede a main shock and are less damaging.


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Figure shows earthquake zones


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6.7 Tsunami:

This is a huge ocean wave produced by displacement of the sea floor; also called seismic

sea wave. The sudden movement of the sea floor upward or down during a submarine

earthquake can generate very large sea waves, popularly called tidal waves but the

Japanese term Tsunami is preferred by geologist. They are caused by great earth quakes

(magnitude 8 +) that disturb the sea floor, but they also result from submarine landslides

or volcanic explosions.

http://www.youtube.com/watch?v=sBkMLYUyUZg&feature=related

http://www.youtube.com/watch?v=sBkMLYUyUZg&feature=related


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CHAPTER SEVEN

Matthew 7:24-27

Jesus Christ said “Anyone who listens to my teaching and follows it is wise, like a person who builds a house on solid rock.

Though the rain comes in torrents and the floodwaters rise and the winds beat against that house, it won’t collapse because

it is built on bedrock. But anyone who hears my teaching and doesn’t obey it is foolish, like a person who builds a house on

sand. When the rains and floods come and the winds beat against that house, it will collapse with a mighty crash.”

7.0 GEOTECHNICAL METHODS OF SITE INVESTIGATION

7.1 Definitions

A site investigation or soil survey is an essential part of the preliminary design work on

any important structure in order to obtain information regarding the sequence of Strata

and the ground water level and also to collect samples for identification and testing.

In addition a site investigation is often necessary to assess the safety of an existing

structure or to investigate case where failure has occurred.

7.2 Objectives

British standard code of practice BS.5930, “site investigation”, lists the following as the

main objectives of a site investigation:

i) To assess the general suitability of the sight for the proposed works.

ii) To enable an adequate and economic design to be prepared.

Definitions

Objectives

Desk study

Site Reconnaissance

Ground Investigations

Site investigation Report

SUMMARY


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iii) To fore see and provide against difficulties that may arise during construction due

to ground and other local conditions.

iv) To predict any adverse effect of the proposed construction on neighboring

structures.

7.3 Steps involved in Site Investigation

7.3.1 Desk study

The desk study is generally the first stage in a site investigation.

It involves collecting and collating published information about the site under

investigation and putting it all together to build a conceptual model of the site.

This model can then be used to guide the rest of the investigation, especially the ground

investigation.

Much of the information gathered at the desk study stage is contained in maps,

published reports, aerial photographs and personal recollection.

7.3.1.2 Source of information

The sources of information available to engineer include geological maps, topographic

maps (ordinance survey maps), soil survey maps, aerial photographs, mining records,

ground water information, existing site investigation reports, local history literature,

metrological records; and river and coastal information.

a) Geological maps: Geological maps provide information on the extent of rock and soil

deposits at a particular site. The significance of the geological information must be

correctly interpreted by the engineer to assist in the further planning of the site

investigation.

b) Topographical maps: These are also called Ordinance survey maps and provide

information on, for example, the relief of the land, site accessibility and the land forms

present

c) Soil survey maps: Also called Pedological soil survey involves the classification,

mapping and description of the surface soils in the area and is generally of main

interest to agriculturalists. It studies top soils 1-1.5m. The surface soil type can

often be related to the parent soil lying beneath; and so, soil types below 1.5m can

often be interpreted from the maps.


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d) Aerial photographs: With careful interpretation of aerial photographs, it is possible

to deduce information on land forms, topography, land use, historical land use; and

geotechnical behavior. The photographs allow a visual inspection of a site when

access to the site is restricted.

e) Existing site investigation reports: These can often be the most valuable source of

geotechnical information. If a sight investigation has been performed in the vicinity

in the past, then information may already exist on the rock and soil types, drainage,

access, etc. The report may also contain details of the properties of the soils and test

results.

7.3.2 Site reconnaissance.

A walk over the site can often help to give an idea of the work that will be required.

Difference in vegetation often indicates changes in subsoil conditions and any cutting,

quarry or river on or near the site should be examined. Site accesses, overhead

restrictions, signs of slope instability are further examples of aspects which can be

observed during the walk over survey.

7.3.3 Ground investigation

7.3.3.1 Site exploration method

Test or trial pits: A test pit is simply a hole dug in the ground that is large enough for

a ladder to be inserted, thus permitting a close examination of the sides. With this

method, ground water conditions can be established exactly and undisturbed soil

samples are obtainable relatively and easily. Depth of 4m can be achieved with this

method.

Hand auger or post-hole auger: The hand auger (attached to drill rods and turned by

hand) is often used in soft soils for boring to about 6m in depth.

Boring rig: In most site investigations the boreholes are taken down by some form of

well-boring equipment and can extend to considerable depths.


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7.3.3.2 Sampling

Two types of soil sample can be obtained which are disturbed sample and undisturbed

sample.

Disturbed sample: The soil sample got as a borehole is being excavated is called

disturbed soil samples.

Undisturbed samples: This is the sample got by driving a core into the ground, carefully

removing it; first be given two coats of paraffin wax on each side and then placed in an

air tight container.

7.3.3.3 Soil profile.

From the results of a site investigation vertical sections (soil profiles) are generally

prepared, showing to scale the sequence and thickness of the strata.

7.3.3.4 Site investigation reports.

The site investigation report is the final product of the exploration program. Site

investigation report involves the following:-

a) Preamble: This is introductory section consisting of a brief summary which gives the

location of the site, the date of the investigation and name of the client, the types and

number of boreholes put down and the equipment used.

b) Description of site: Here a general description of the site is given; whether it is an

open field or a redevelopment of a site where old foundation, walls e.tc remain. A

map showing the site location and the positions of any boreholes put down, is usually

included in the report.

c) Description of subsoil conditions encountered:

This section should consist of a short and readable description of the general subsoil.

Conditions over the site with reference to the bore hole journals.

Generally the significance of any in-situ testing carried out is mentioned.

d) Borehole journals: It is a list of all the materials encountered during the boring. A

Journal is best shown in sectional form so that the depths at which the various

materials were met can be easily seen. It should include a note of all the information


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that was found, ground water conditions, numbers and types of samples taken, list

of in-situ tests, time taken boring. etc.

e) Description of laboratory soil tests. This is simply a list of the tests carried out

together with a set of laboratory sheets showing particle size distribution curves,

liquid limit plots etc.

f) Conclusions. It is in this section that firm recommendations as to possible

foundation types and modes of construction should be given.


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CHAPTER EIGHT

Politicians are people who, when they see light at the end of the tunnel, order more tunnel.

Sir John Quinton (1929- ) British banker

8.0. TUNNELING

8.1 Definitions.

Tunnels may be defined as the underground routes or passages, excavated through the

rocks or soft ground, without disturbing the overlying rocks or soil covers.

The subways below the ground by first removing the overburden by making open cuts

and then laying roof slabs are therefore not included in tunnels.

8.2 Merits and demerits of tunnels.

8.2.1 Merits of tunnel.

i. Tunnels prove to be more economical than the open cuts beyond certain depths.

ii. Tunnels avoid disturbing and interfering with surface life and traffic during

construction

iii. Tunnels prove to be better protected than bridges during war times and bombing

operations.

iv. Tunnels prove to be cheaper for carrying water, sewage, gas, etc as compared to

their being taken in open cuts.

v. Tunnels do not occupy any space on the surface.

Definitions

Merits & Demerits of tunnels

Tunnel Approaches

Shape & Size of Tunnel cross-section

Types of Tunnels

Geological considerations required for successful tunneling

operations in consolidated and unconsolidated rocks.

SUMMARY


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8.2.2 Demerits

i) The construction of tunnels is a costly process

ii) It requires skilled labour and technical supervision.

iii) Tunneling requires specialized and sophisticated equipments.

iv) The excavation of tunnels takes long period.

8.3 Tunnel approaches

Tunnels are joined at either ends by open cuts, called approaches. The approach is very

short (fig a) in case of steep hill slopes; and very long when the hill slopes is very flat (fig

b)

Steep hill overlaying soil

side

Approach

a) Short approach

Flat hill side overlaying soil

Approach

Tunnel

Tunnel


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b) Long approach

8.4 Shape and size of tunnel cross-sections.

8.4.1 Shapes of tunnel cross-section

The tunnels may be constructed in different shapes depending on the nature of soil/rock

and other practical considerations. The three types of sections, which are commonly

adopted, are:-

i) D-shape

ii) Circular shape

iii) Horse –shoe shape

(i) D-shape


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(ii) Circular shape


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(iii) Horse-shoe shape

i) D-Shaped tunnel.

This is usually adopted in rocks, where unlined tunnels are proposed to be

constructed. Such a section has an arch roof and straight vertical sides. The arch

roof can easily take vertical loads and transfer them to the sides.

The sides may be constructed in R.C.C in case of soft soils. This section is suitable

for subways and for navigation tunnels. This section has a nearly flat invert, which

provided additional working floor space, helpful during driving and a flat floor for

moving equipment.

These are the principal advantages for this section and make it the usually adopted

section for highway and railway tunnels (subways)

ii) A circular section.

This is usually lined and offers strong resistance to external pressure from water

bearing soils or soft grounds; as well as to the internal pressure of fluids, if passing

through the tunnel.

Such a shape is most suitable to withstand internal and external forces and provides

the largest cross- sectional area for the least perimeter. It is therefore, most suitable

for sewers, water conducts, etc. Circular section, however, is not suitable for roads

and railways, as more filling will be required for obtaining a flat base. This is best

suitable for non-cohesive soils and for tunnels driven by shield-method.

iii) A horse shoe section

This is a popular shape, having a semi-circular roof together with arched sides and a

curved invert. When lined, this cross section offers good resistance external ground

pressure and serves to combine the advantages of both the D-shaped and circular

sections. It is the best shape suitable for traffic tunnels, as the floor of the tunnel is

nearly flat, which also provides working space to the contractor, for storing materials

during construction, besides providing flat base for moving traffic. This section is

found to be most suitable for soft rocks and is also suitable for carrying water or

sewage. This shape is very commonly used for highway and railway tunnels in all

countries of the world.


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8.4.2 Size of Tunnel cross-section.

The size of the tunnel is determined from its utility requirements aspect. For highway

and railway tunnels, the size will depend upon the number of lanes and tracks to be

passed through the tunnel. To avoid too large sizes, sometimes twine tunnels, placed

side by side, may be constructed, at suitable spacing, such that the disturbance caused

in the ground due to the construction of one tunnel does not affect the other.

The size of the section in general, will however, be governed by the thickness of lining,

provisions required for drainage, the clear opening required for drainage, the clear

opening required for passing the volume and nature of traffic, the opening required for

passing the designed discharge, etc.

8.5. Types of tunnels

Depending upon their use, the tunnels may be classified into the following groups;-

a) Traffic tunnels

b) Hydropower tunnels

c) Public utility tunnels

a) Traffic tunnels.

The traffic tunnels include all those tunnels, which are constructed for passing railway

tracks, roads, pedestrians, or even navigational traffic. A traffic tunnel, thus, provides a

direct transportation link between two places, separated by obstacles such as a

mountain, a hill, a water body like rive or sea, or even densely populated land. Traffic

tunnels may vary in length from a few meters to many kilometers.


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b) The Hydro power tunnels.

The tunnels which are excavated through rocks for the purpose of conveying water from

one point to another, in connection with hydro-power generation, are called hydro-power

tunnels. When such a tunnel is excavated through a hill to carry water from one point

to another by gravity, it is called a discharge tunnel and when the tunnel is steeply

graded to feed water under great pressure to turbines, etc. it is called a pressure tunnel

as shown below.

Reservoir Discharge tunnel

Pressure tunnel

Power house


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c) The Public Utility Tunnels

All other tunnels excavated for other public uses, such as for carrying sewage, cables, oil

supplies, drinking water, etc. are classified under this category.

8.6 Geological considerations required for successful tunneling

operations in consolidated and unconsolidated rocks.

Like other civil engineering projects, such as dams, reservoirs, buildings, roads, bridges,

docks, harbors, etc, tunnels are also very important civil engineering projects, but with

the primary difference that tunnels lie underground within the rocks; while the other

structures lie on the surface.

For this reason alone, the safety and stability of tunnels become much more important.

Another difference between tunnels and dams is with reference to the scope of selection

of the site whereas, in the case of dams, etc., the final selection of the best site is made

after carefully considering the relative merits and demerits of the various alternative

sites; there is no such choice in the case of tunnels, since they are dependent upon the

bus route, or course of railway track, location of power house, location of town ship, etc.

Since these locations are fixed, the places where tunnels are needed also get

automatically fixed, thereby usually leaving no scope for choosing a better alternative

site. There may of coarse exist a little flexibility in fixing the alignment of tunnel like

other civil engineering structures, tunnels too need favourable geological conditions of

their sites for obtaining success in their construction. As usual, success here also means

safety, stability, economy and non- troubling future performance. To achieve these aims,

geological investigations are required to be made at the tunnel site.

8.6.1 Tunneling in consolidated rocks

Tunneling in hard crystalline and massive rocks like Granites, Diorites, Gabbros,

Basalts, sandstones, Quartzite, Granitic Gneisses and Marbles usually present no major

problems.

These are excavated by using conventional rock blasting methods which involve

exploding suitable quantities of right type of explosive in especially drilled blast holes.

Each blasting round is usually followed by a Mucking period during which the blasted


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fragments are removed. Excavations so created in these rocks are mostly self-supporting

and no major support required. Although cost of blasting may be high with hard rocks,

it is often more than compensated by the self- supporting character of the rocks.

In soft rocks like lime stones, Dolomites, argillaceous, sand stones, schists and slates,

etc. blasting costs are comparatively lower, but involves a lot of expenses and delays in

erecting temporary and even permanent living, which become a major consideration for

safety reasons.

8.6.2 Tunneling in unconsolidated rocks

Tunneling in unconsolidated rocks or loose sediments is known as soft-ground tunneling

and is comparatively complicated than in solid rocks. The complications arise because

of:-

i) Structural weakness of the sediments forming the ground.

ii) Low cohesion and internal friction of the particles of ground.

iii) Uncertainty of ground-water conditions


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CHAPTER NINE

You can teach someone up to a University, but you can’t teach that person how to think.

9.0. PROCESS OF WEATHERING AND DENUDATION

9.1 Introduction: General, sources and definitions

The rock surface of the continents of the Earth, on which we are living, is undergoing

constant and continuous destruction, a process called denudation.

Denudation is the process by which the land areas are continually being reduced and

their shape modified by weathering and erosion.

Rocks exposed at Earth’s surface are constantly being altered by water, air, changing

temperature and other environmental factors. The term weathering refers to the group

of destructive processes that change the physical and chemical character of rock at or

near Earth’s surface. The tightly bound crystals of any rock can be loosened and altered

to new minerals by weathering.

It is important to distinguish between weathering and erosion and between erosion and

transportation. Weathering breaks down rocks that are either stationary or moving.

Erosion is the picking up or physical removal of rock particles by an agent such as

streams or glaciers. Weathering helps break down a solid rock into loose particles that

are easily eroded.

Introduction

Types of weathering

Agents of Erosion

Factors affecting rate of weathering

Importance of weathering

Shortcoming of weathering

SUMMARY


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Most eroded rock particles are at least partially weathered, but rock can be eroded before

it has weathered at all. A stream can erode weathered or un-weathered rock fragments.

After a rock fragment is picked up (eroded), it is transported. Transportation is the

movement of eroded particles by agents such as rivers, waves, glaciers, or wind.

Weathering processes continue during transportation.

A boulder being transported by a stream can be physically worn down and chemically

altered as it is carried along by the water.

9.2 Types of weathering.

These are three types of weathering namely:-

i) Mechanical weathering or disintegration.

ii) Chemical weathering or decomposition

iii) Biological weathering.

9.2.1 Mechanical weathering or disintegration

This is the breakdown of rocks into small particles by the action of temperature, by

impact from rain drops and by the abrasion from mineral particles carried in the wind.

9.2.1.1 Products of mechanical weathering

The products of mechanical weathering include everything from huge boulders found

beneath the cliffs to the smallest silt.

9.2.1.2 Processes most commonly involved in mechanical

weathering.

1. Mechanical unloading

This is the vertical expansion due to the reduction of vertical load by erosion.

This will open existing fractures and may permit the creation of new fractures.

2. Mechanical loading

This is impact on rock and abrasion, by sand and silt size. Wind borne particles that

occur in deserts, impact on soil and weak rocks, by raindrops during intense rainfall

storms.


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3. Thermal loading.

This is expansion by freezing water in pores and fractures in cold regions or by the

heating of rocks in hot regions.

4. Welting and drying.

Expansion and contraction associated with the repeated absorption and loss of water

molecules from mineral surfaces and structures.

5. Crystallization.

This is expansion of pores and fissures by crystallization within them, of minerals that

were originally in solution.

Note: Expansion is only severe when crystallization occurs within a confined place.

6. Pneumatic loading.

The repeated loading by waving of air trapped at the head of fractures exposed in the

wave zones of a sea cliff.

Some terms used

1. Frost-heaving- gentle rising and falling in regular alternation

This occurs when the freezing of the soil results in the formation of layers of segregated

ice at shallow depths.

The frost heaving of foundations of buildings is also caused by forces originating in the

active layer and is a common problem is the Arctic – extremely cold.

Buildings which are heated can be placed a little above ground- level with a large air

space beneath them. Cold air in winter then circulates under the building and contracts

the heating effect from it.

Piped services to the buildings are also placed above ground level to prevent their rupture

by ground movement.

2. Insolation.

In hot climates, when a rock surface is exposed to a considerable daily range of

temperature as arid and semi-arid regions, the expansion that occurs during the day

and the contraction at night, constantly repeated, weaken the structure of the rock. The

outer heated layers tend to pull away from the cooler rock underneath and flakes and

slabs split off, a process known as exfoliation. This weathering is called Insolation.


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3. Un loading

One result of denudation is to reduce the load on an area as the removal of the rock

cover proceeds, leading to relief of stress in the rocks. The unloading allows a small

vertical expansion which gives rise to the formation of “sheet” of rock by the opening of

joints parallel to the ground surface.

This is frequency seen in igneous rocks such as granite intrusion, where the sheet

jointing is developed in the upper part of the mass; the ‘Sheets’ or slabs of a rock are

commonly up to a meter or so in thickness

9.2.2 Chemical weathering.

This is the breakdown of minerals into new compounds by the action of chemical agents;

such as acid in the air, in rain and in river water; although they act slowly, produce

noticeable effects especially in soluble rocks. The rate of chemical weathering depends

on temperature, the surface area and the amount of water. Chemical weathering causes

the old minerals to disintegrate and to form new minerals. Minerals which are originally

formed at lower temperatures in the original igneous rocks during the process of cooling

of magma prove more resistant to chemical weathering compared to those which were

formed at high temperatures during the cooling of Magma.

9.2.2.1 Processes of chemical weathering

Processes are most commonly involved in chemical weathering are listed below and their

rate of operation depends upon the presence of water and is greater in wet climates than

in dry climates. Some commonly occurring processes in chemical weathering are:

1. Solution.

This is dissociation of minerals into ions greatly aided by the presence of carbon dioxide

(CO2) in the soil profile, which forms carbonic acid (H2Co3) with percolating rain water.

2. Oxidation

This is the combination of oxygen (O2) with a mineral to form oxides and hydroxides or

any other reaction in which the oxidation number of the oxidized elements is increased.

3. Reduction.


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The release of oxygen (O2) from a mineral to its surrounding environment; ions leave the

mineral structure as the oxidation number of the reduced element is decreased.

4. Hydration.

This is the absorption of water molecules into the mineral structure.

Note: This normally results in expansion; some clay expands as much as 60% and by

admitting water hastens the process of solution, oxidation reduction and

hydrolysis.

5. Hydrolysis

Hydrolysis is the reaction with water. Hydrogen ions in percolating water replace mineral

cations; no oxidation reduction occurs. In other words, hydrolysis is a chemical reaction

in which a compound reacts with water causing decomposition and the production of

two or more other compounds.

6. Leaching

This is the migration of ions produced by the above processes.

Leach. (To drain away from soil when dissolved in rain water, lose a mineral or chemical

dissolved in rain water.

Note: The mobility of irons depends upon their ionic potential. Calcium (Ca),

Magnesium (Mg), Sodium (Na), and Potassium (K) are easily leached by moving

sodium water, Iron (Fe) is more resistant, Silicon (Si) is difficult to leach and

Aluminum (Al) is almost immobile.

7. Cation exchange.

This is the absorption onto the surface of negatively clay of positively charged cations in

solution especially Calcium (Ca), Hydrogen (H), Potassium (K), and Magnesium (Mg).

9.2.2.2 Conclusion

The speed and severity of weathering in wet climates depends essentially upon the

activity of the root zone, i.e. the rate of growth of vegetation and production of carbon

dioxide (Co2 ) in the root zone and the frequency with which percolating rain water can

flush weathered constituents from the weathering profile. Chemical weathering is seen

readily in rocks containing the minerals Halite (Nacl), Anhydrite (CaSo4) and Gypsum

(CaSo4.2H2O).


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The most easily weathered are lime stones; of greater resistance are sandstones and

shales; igneous rocks (excluding certain volcanic rocks that weather rapidly) and

Quartzite are the most resistant.

Note: In dry climates, chemical weathering is superficial and much retarded by the lack

of water, producing thin zones of weathered rock. In very dry climates mechanical

process are the dominant weathering agents.


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9.2.2.3 End Product of Chemical Weathering of common Minerals

NO Parent mineral

constituent elements in reaction

Weathering process Weathering product End product or final deposition.

1 Quartz SiO2 No chemical weathering Sand grains Sand stone

2 Potassium Felspars

(KALSi3O8

K

Al, SiO

SiO2

+Co2 (carbonation)

+H2O(Hydrolysis)

K2CO3

Clay (Al2Si2O5(OH)4)

Soluble and colloidal silica

Some is transported in oceans

Some is used by plant life & some is

absorbed on or taken into certain clays.

Shale (Chalcedony) chert.

3 Plagioclase Felspars

(NaAlSi3O8

and(CaAl2 Si2O8)

Na

Ca

Al, Si, O

SiO2

+Co2 (carbonation)

+Co2 (carbonation)

+H20 (Hydrolysis)

Ala2CO3

Calcite (caco3)

Clay

Soluble and colloidal

Silila

Dissolves in ocean limestone

Shale (Chalcedony

Chert.

4 Muscovite Produces the same products as potassium felspars.

5 Ferro magnesian

minerals

They form the same weathering products as the felspars, plus

Fe +O(oxidation) Hematite (Fe2O3 Sedimentary deposits of

+O+H2O(oxidation & limonite (FeO(OH) iron ore

Mg hydrolysis) Mg Co3 Some replaces calcium in

+ CO2 in lime stone to form Dolostone and

(not clearly known) some goes into certain clay minerals


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9.2.3 Biological Weathering

This describes those mechanical and chemical changes of the ground that are directly

associated with their activities of animals and plants. When present, microbial activities

can change the chemistry of the ground close to ground level.

9.2.3.1 How does this type of weathering come about?

Burrowing animals and plant roots penetrate the ground and roots produce gasses

which increase the acidity of the percolating rain water.

By these processes a covering layer of weathered rock is formed on a land surface.

Normally the upper layers of this cover are continually removed, exposing the fresher

material beneath it to the influence of the weathering agents. In this way, the work of

denudation continues. Agents of erosion include: - rivers, wind moving ice. Water

waves, etc. Weathering effects which are small in themselves but noticeable in the

aggregate can be attributed to plants and animals (Biotic weathering). Plants retain

their moisture and any rock surface on which they grow is kept damp, thus promoting

the solvent action of the water. The chemical decay of the rock is also aided by the

formation of vegetable humus, i.e. organic products derived from plants and this is

helped by the action of bacteria and fungi. Organic acids are thereby added to

percolating rain water and increase its solvent power. Bacteria species may live in the

aerobic and anaerobic pore space of the weathering zone and mobilize C, N, Fe, S and

O; thereby assisting the process of weathering and sometimes attacking concrete and

steel. Their mineral by-products can accumulate and cause expansion of the ground if

not washed away by percolating water. The mechanical break up of rocks is hastened

when the roots of plants penetrate into cracks and wedge apart the walls of the crack.


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9.3 Agents of erosion

The erosion is caused mainly by the three agents:-

i) Water

ii) Wind

iii) Ice

The fourth agent which helps is gravity.

9.3.1 Water

Water is the most important agent of erosion responsible for the maximum havoc it

creates in the form of erosional damages to the land surface.

It may act in three forms i.e. as falling drops, running overland flow and as running

rivers and streams. The erosion caused by water is generally quite devastating and may

create various engineering problems, if not properly checked or accounted for, while

planning the engineering projects.

9.3.2 Wind

The earth, as you know is surrounded by an environment of gases, called the

atmosphere. The movement of the atmosphere in a direction parallel to the Earth’s

surface, is wind, where as the vertical movements of the atmosphere are termed as air-

currents. The cause of wind formation is the subject of a science called Meteorology,

and is beyond the scope of this program. We under engineering Geology are mainly

concerned with the geological work done by wind, in the form of erosion and consequent

deposition of the eroded material.

Like water, wind is also an agent of erosion, transportation, as well as deposition. It is

quite an effective agent of erosion in deserts and arid dry areas.

9.3.3 Erosion by moving ice.

A glacier is a mass of moving ice, which causes erosional of the surface over which it

moves. The third agent of erosion i.e. ice or glaciers may also cause a lot of erosional

damages, although it becomes slightly less important in a tropical country like Uganda.

The eroded material is carried in an embedded state by the glacier over some distance

and then deposited at some place(s) as and when the sediment load gets separated out

due to over-loading or sudden disturbance or melting of glacier itself. A glacier, like

water and wind, thus act as an agent of erosion, transportation, as well as deposition.


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About 10% of our present land of the globe is covered by glaciers. They are slow erosive

agents, much less effective than water, as far as the overall erosion is concerned.

However, in areas of excessive snow falls, such as in mountain tops and solar regions,

they become quite effective over a period of time and are thus believed to have developed

many land forms (i.e. geological features) of the world

9.4 Factors affecting rate of Weathering

1. Mineralogy

Some minerals are more susceptible to weathering. The dark minerals are also more

affected by thermal weathering than light coloured ones. A rock that is polymineralic is

more subject to destruction than one that is monomineralic. This is because coefficients

of linear expansion and therefore undergo different deformations with variations in

temperature with protracted temperature variations, mutual cohesion between

individual grains is disrupted and the rock disintegrated.

2. Texture

In principle, the finer grained rock is the greater the surface area exposed and hence

the greater the surface area are exposed and hence the greater intensity of weathering.

However, if a rock has coarse grains that are easily weathered, the great holes left may

weaken the rock rapidly and therefore enhance the rate of weathering.

3. Discontinuities

These provide surfaces along which weathering can take place easily (i.e. where agents

of chemical weathering can penetrate and act). They include joints, faults, bedding

planes and cleavage. The fractures are gradually widened by weathering until the rock

is completely split into parts.

4. Climate

Regions with large diurnal range (daily temperatures variations) undergo the most

intensive thermal weathering.

This is most pronounced in deserts.


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9.5 Importance of weathering

1. Leads to the breakdown of rocks into smaller particles until soil is formed which is

valuable agricultural uses

2. Weathered land forms are tourist attractions.

3. Weathered land forms are used for research purposes.

4. Weathering products transported to the sea by rivers as dissolved solids make sea

water salty and serve as nutrients for many marine organisms.

5. Some metallic ores, such as those of copper and aluminum, are concentrated into

economic deposits by chemical weathering.

9.6 Short coming of weathering

1. Affects buildings and other constructed infrastructures.

2. It encourages erosion especially rapid weathering


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CHAPTER TEN

Psalm 118:22

The stone (Jesus Christ) that the builders (Human Beings) rejected has now become the cornerstone (indispensable).

10.0 GEOLOGICAL ASPECTS OF BUILDING STONES AND

AGGREGATES.

Introduction

Uses of stones

Seasoning of stones

Characteristics of stones

Decay or degradation of stones

Preservation of stones

Quarry and Quarrying

SUMMARY


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10.1 Introduction

10.1.1 Rock

A rock is a term used to name a solid portion of the earth’s crust. It has no definite

shape and chemical composition.

The rocks have one or more than one mineral. Those having one mineral are known as

monomineralic and those having several minerals are known as polymineralic minerals.

Quartz, pure gypsum, and Magnetite are examples of monomineralic rocks and granite,

Basalt and gabbros are polymineralic rocks. The rocks are named after the predominant

mineral in it. A rock having calcium carbonate mineral predominant is termed as

calcareous rock. Similarly, rocks predominant in clay are called argillaceous rocks.

10.1.2 Stone

A stone is always obtained from a rock. The rock quarried from quarries is called stone;

quarried stone may be in the form of stone block, stone aggregate, stone slab, and stone

lintel.

Stone, inorganic mineral or soil concretion of the earth, of sedimentary, igneous, or

metamorphic origin, commonly used in building, civil engineering, manufacturing and

art. Some of the building stones are basalt, flint, granite, lime stone, marble, porphyry,

sand stone, slate and flagstone.

Ornamental stones, other than precious stones or gems, include alabaster, fluorite

Jade, Jasper, lapis lazuli, laboradorite and malachite.

10.2 Uses of stones

1. Masonry work for lintels, floor slabs, paving roads, Boulders on roads, aggregates in

concrete.

2. Manufacture of cement and lime

3. Ballasts used in railway tracks.

4. Construction of Masonry Dams

5. Decoration

6. Damp proof course


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10.3 Seasoning of stone

Stones have natural moisture and the moisture is known as quarry sap. This quarry

sap renders the stone blocks comparatively soft and makes them easily workable.

Therefore the stones should be dressed soon after quarrying. The quarry sap is a mineral

solution which chemically reacts with mineral constituents of stone during drying and

makes the stone hard and compact. It is important to achieve full hardening of freshly

quarried stones before they are allowed to be used in Masonry work. The full hardening

of the stone is achieved by exposing the stone to open air up to 6-12 months, during

this period, quarry sap dries up from stones completely, and this process is known as

seasoning of stones.

10.4 Characteristics of stones

The most important physical properties of rocks which are required for engineering

purposes are their durability, hardness, toughness, porosity and strength. These

properties are dependent on the mode of occurrence, type and condition of the rocks,

and are modified by their subsequent treatment when exposed to the solvent action of

acid or salt waters, great changes of temperature and when subjected to mechanical

pressure, abrasion or impact. These are:-

1. Durability: This is the ability of a stone to last for a long time, especially without

sustaining damage or wear.

2. Strength: The ability of a stone to withstand force, pressure, or stress.

3. Hardness: The state or quality of a stone being firm, solid and compact.

4. Toughness: This is the resistance of a stone to breaking under repeated hitting and

bending forces.

6. Fineness of grains

7. Compactness

8. Weight

9. Resistance to wear

10. Appearance

11. Porosity and absorption

12. Resistance to fire


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13. Resistance to weathering

10.5 Decay or degradation of Stones

Exposed stones have to withstand harmful effects mainly caused by:-

1. Temperature variation

Stones are composed of several minerals which have coefficients of expansion. Rise or

fall of temperature causes differential expansion and contraction of minerals causing

deterioration. Alternatively, a rise and fall temperature without differential expansion

or contraction also causes deterioration.

2. Wetting and drying stones

Rain, dew and frost cause wetting of stones and sunshine causes drying.

Alternating wetting and drying causes disintegration of stones.

3. Frost action

In hilly regions and other cold regions, water presentation pores of stone may freeze due

to cold. The water expands after freezing and thus causes splitting of the stones.

4. Polluted atmosphere

The atmosphere may be changed heavily with harmful gases and fumes. Such an

atmosphere prevails in industrial cities.

The gases tend to form acids in atmospheric moisture action with calcium carbonate

(CaCo3) of stones and causes disintegration.

5. Living organisms.

There are some living organisms which slowly act upon stones and cause their

deterioration, lichens destroy lime stones and worms destroy all stones except granite.

6. Vegetable growth

Certain trees and other vegetations may grow at fracture, or joints of the stones the

roots of vegetations attract moisture and keep the stones always damp. Trees growing

expand and push the adjacent stones.

7. Rain water.

Rain water causes physical disintegration of rocks by physical as well as chemical

action, wetting of stone as well as drying by sunshine is a physical action.


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Rain water descending through the atmosphere absorbs gases like carbon dioxide

hydrogen, sulphide, etc. These both form acids with rain water and render water

chemically aggressive leading to disintegration.

8. Wind.

Wind also helps in deterioration of stones. Strong winds cause fine particles to strike

against the stone, hence causing it to decay. Winds also help rain water to penetrate

and may freeze during winter

H2SO4 + CaCo3 CaSo4 + Co2 + H2O

10.6 Preservation of stones

A good preservation should posses the following properties.

1. Economical, non-corrosive and harmless to health

2. It should maintain its effectiveness for a long time.

3. It should easily penetrate into the stone interior

4. Application should be easy on the stone surface.

5. It should not develop sectionable, objectionable colors.

6. It should not allow deep penetration of moisture.

7. Preservative should be hard enough to withstand atmosphere.

10.6.1 Examples of preservatives

1. Paint

2. Lean seed oil

3. Paraffin

4. Plastering and painting

5. Using Barium hydroxide.


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10.7 Quarry and Quarrying

The site from where stones are excavated is called a quarry.

The process of taking out stones from a quarry is known as quarrying of stones.

Open excavation from which any useful stone is extracted for building and engineering

purposes and the operations required to obtain rock in useful form from a quarry.

The two principal branches of the industry are the so-called dimension-stone and

crushed-stone quarrying. In the former, blocks of stone such as marble, are extracted

in different shapes and sizes for different purposes. In the crushed- stone industry,

granite, lime stone, sand stone, or basaltic rock are crushed for use principally as

concrete aggregate or road stone. There is a difference between quarrying and mining.

In case of mining, all the excavation process is carried out underground whereas all the

operations of quarrying are at ground level and under exposed conditions.

10.8 Selection of Quarry site

The following points should be considered while choosing a quarry:-

1. Distance from quarry to road, train, etc., should not be large.

2. Sufficient stones should be assured from site.

3. Availability of equipment and labor.

4. Quality of stone available from quarry site should be good.

5. Drainage from quarry should be easy.

6. Adequate facility for transportation of stone should be available

7. Geological formation of site should be properly studied.

8. Site should be away from residence

10.9 Different methods used in stone Quarrying

Quarrying is carried out by different methods and equipment, such as hand tools,

explosives, or power saws, and by channeling and wedging, according to the purpose

for which the stone is extracted. Hand tools alone may be used for quarrying stone that

lies in easily accessible beds. The principal hand tools are the drill, hammer, and wedge.

A row of holes several centimeters apart is made with the drill and the hand hammer,

partly through the layer, or stratum, perpendicular to its plane of stratification and


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along the line at which it is desired to break the stone. Each hole in a long row is filled

with three wedges, shaped so that one may be driven down through the others, the

method being known as plug and feathers; by striking each plug a sharp blow with a

hammer, hitting them in succession, and by repeating the operation several times, the

combined splitting force of the plugs and feathers finally becomes great enough to

rupture the rock.

Explosives are most commonly employed for detaching large blocks of stone, which are

then split and broken into smaller stones by wedges or by the plug-and-feathers method,

or crushed by a heavy steel ball weighing several tons. In this method of quarrying, the

drill holes are put down to the depth to which it is required to break the rock and are

then partly filled with some explosive that is discharged by the usual methods of

blasting. To obtain finely crushed stones for concrete, primary crushers, of the jaw or

gyratory type, and secondary crushers are used to reduce the size of the rocks.

Channeling is the process of cutting long, narrow channels in rock to free the sides of

large blocks of stone. Channeling machines, or channelers, formerly steam driven; have

now been generally replaced by gasoline or electric engines. These are self-propelling

and move a cutting edge back and forth along the line on a rock bed on which the

channel cut is to be made. The channel cut is sunk deep enough to permit the insertion

of wedges by which the rock is split, the cut or groove guiding the fracture. The

channeling and wedging process of quarrying is extensively used in quarrying marble,

sandstone, limestone, and the other softer rocks, but is not successful for granite and

other hard rocks.

Another method of cutting is by the combination of a power saw, an abrasive, and water

as a lubricant and a coolant. The saw cuts a narrow channel, the primary or initial cut,

which is then either expanded by a wedge or is blasted. This method is used in slate,

granite, and limestone quarries.

An automatic channel burner has recently come into commercial use in dimension-

stone quarrying. It resembles a handheld burner held vertically in a frame, with an

electric motor moving the whole unit slowly down a track. It makes a more even cut,

does not require the presence of an operator, and wastes less rock. The unit is controlled

by a computer.


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CHAPTER ELEVEN

Genesis 21:19

Then God opened Hagar’s eyes, and she saw a well full of water. She quickly filled her water container and gave the boy

(Ishmael) a drink.

Genesis 26:32-33

And it came to pass the same day that Isaac’s servants came and told him concerning the well which they had dug, and

said unto him, we have found water. And he called it Sheba: therefore the name of the city is Beersheba unto this day.

11.0 GEO-HYDROLOGY

11.1 Origin of ground water.

The major source of ground water is rainfall and this groundwater which originates

from precipitation is called meteoric water.

Besides this major source, two other minor sources of ground water are:-

Connate water: The sea water trapped in the pores of rocks that originated in shallow

seas of the past geological times.

Juvenile: The water which comes chiefly from volcanic emanations in the form of water

vapor.

Origin of groundwater & Definitions

The hydrologic cycle

Occurrence of groundwater

Wells

Aquifers

Springs

Isotropy & Anisotropy

Potentiality of different rocks as Aquifers

Groundwater prospecting

SUMMARY


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Neither of these two minor sources is significant in terms of the total volume of fresh

underground water.

11.2 Definition

Groundwater may be defined as:-

Groundwater is Surface water accumulating because of seepage (infiltrations) and

returning to the surface as springs and through wells. Ground water is the underground

water that occurs in the saturated zone of variable thickness and depth below the earth’s

surface. Precisely to say, Groundwater is water beneath the surface that can be collected

with wells, tunnels or discharge galleries or that flows naturally to the earth’s surface

via seeps or springs. Groundwater is the fluid mostly encountered in engineering

construction. It is derived from many sources but mostly it comes from rainfall and

melting of snow. The passage of water through the surface of the ground is called

infiltration and it’s down ward movement to the saturated zone and depth is described

as percolation. Cracks and pores in the existing rocks and unconsolidated crystal layers,

make up a large underground reservoir, where part of precipitation is stored.

11.3 The hydrologic cycle.

The movement of water and water vapor from the sea to the atmosphere, to the land

and back to the sea and atmosphere again is called the hydrologic cycle.

The hydrologic cycle may be represented diagrammatically as shown below.


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Water in the sea evaporates under solar radiation and clouds of water vapor move over

the land areas. Precipitation occurs as water begins to flow back into the sea. Some of

it infiltrates into the soil and percolates into the saturated ground zone beneath the

water table or phreatic surface. The water in this zone flows through aquifers to river

channels or sometimes directly into the Sea. The water that infiltrates also feeds the

surface plant life and sometimes gets drawn up vegetations where transpiration takes

place on the leaves.

Water remaining on the surface partially evaporates into vapor and the remaining water

that has not infiltrated or evaporated runs as surface water/Run-off to the river

channels and arrives back to the sea.

The whole cycle will then start again, hence the hydrologic cycle.

11.4 Occurrence of Groundwater

The rainfall that percolates below the ground surface passes through the voids of the

rocks and joins the water table. These voids are generally inter-connected permitting

the movement of the ground water. But on some rocks, they may be isolated and this

preventing the movement of water between the interstices. Evidently, the mode of

occurrence of ground water depends largely upon the type of formation and hence upon


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the geology of the area. All the materials of variable porosity (or interstices) near the

upper portion of the Earth’s crust can be considered as a potential storage place for the

ground water and may therefore be called as the ground water reservoir.

The volume of water contained in an area, i.e. the water storage capacity of the ground

water, is dependent upon:-

i) The porosity of the rocks

ii) The rate at which water is added to it by infiltration.

iii) The rate at which water is lost from it by evaporation, transpiration, seepage to

surface courses and withdrawal by man.

Porosity

Porosity is the percentage of rock or sediment that consists of voids or openings. It’s a

measurement of a rock’s ability to hold water. Porosity defines the maximum amount of

water that can be stored in the rock; but does not ensure the storage of underground

water.

Total volume of voids in the aggregate i.e. the volume of water require to

Porosity = saturate the dry sample (Vv)

Total volume of the aggregate (V)

It is generally denoted by the letter Neeta (η)

Therefore η = Vv x 100%

V

Porosity, in fact, depends upon the shape, packing and degree of sorting of the

component grains in a given material.

(A) (B)


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Uniform and well sorted grains (A) give rise to higher porosity because the grains of (A)

are all about equal in size; whereas, heterogeneous grains (B) with irregular

arrangements decreases the porosity because in (B) smaller grains fill the spaces

between the larger grains, thus reducing the volume of void space.

Permeability

Permeability is the ability of a rock or unconsolidated formation to transport or pass

water through itself. Permeability refers to the capacity of a rock to transmit a fluid such

as water or petroleum through pores and fractures. In other words, permeability

measures the relative ease of water flow and indicates the degree to which opening in a

rock interconnect. The distinction between porosity and permeability is important.

A rock that holds much water is called porous; a rock that allows water to flow easily

through it is described as permeable. Most sandstones and conglomerates are both

porous and permeable. An impermeable rock is one that does not allow water to flow

through it easily. Unjointed granite and schist are impermeable. Shale can have

substantial porosity, but it has low permeability because its pore is too small to permit

easy passage of water.

Table showing porosity and permeability of sediments and rocks

Sediments Porosity (%) Permeability

Gravel 25 to 40 Excellent

Sand (clean) 30 to 50 Good to excellent

Silt 35 to 50 Moderate

Clay 35 to 80 Poor

Rock

Conglomerate

Sand stone

10 to 30 Moderate to excellent

- We sorted, little cement 2 0 to 30 Good to very good

- Average 10 to 20 Moderate to good

- Poorly sorted, well- cemented 0 to 10 Poor to moderate


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- Shale 0 to 30 Very poor to poor

- Lime stone, dolomite 0 to 20 Poor to good

- Cavernous limestone Up to 50 Excellent.

Crystalline rock

- Un-fractured 0 to 5 Very poor

- Fractured 5 to 10 Poor

- Volcanic rocks 0 to 50 Poor to excellent


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Water table

This is a static level of water in wells penetrating the zone of saturation

Perched water table

This is the top of a body of ground water separated from the main water table beneath

it by a zone that is not saturated.

Drainage of Ground water

This is the extraction of water from below the water table through wells, infiltration

galleries, springs, etc. The water is, thus, drained from the ground water reservoir, either

under some natural phenomena (like springs) or it can be drained artificially by

constructing wells and lifting water through them. The water so drained may be to fulfill

domestic, rural, municipal or industrial water demands.

Specific yield

The volume of ground water extracted by gravity-drainage from an aquifer is known as

the yield and when it is expressed as the ratio of the volume of the total material drained,

and then it is known as the Specific field.

Specific field = Volume of water obtained by gravity drained x 100


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Total volume of the material drained or dewatered

Specific retention or field capacity

The quantity of water retained by the material against the pull of gravity is termed as

the specific retention or the field capacity.

Specific retention = Volume of the water held against gravity drainage x 100

Total volume of the material drained

Note: It is evident that the sum of the specific field and specific retention is equal to its

porosity.

11.5 Wells

Water well is a hole usually vertically excavated in the earth for bringing ground water

to the surface.

A well is man-made hole in the ground from which water can be withdrawn.

11.5.1 Types of wells

The wells may be classified into two types:-

1). Open wells

2). Tubes wells.


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1. Open wells or Dug wells

Open wells are generally open masonry wells having comparatively bigger diameters and

are suitable for low discharges of order 1-5 liters per second. The diameter of open wells

generally varies from 2 to 5m in depth. The walls of an open well may be built of precast

at ring or in brick or stone masonry. The field of an open well is limited because such

wells can be excavated only to a limited depth where the ground water storage is also

limited.

Types of open wells

Open wells may be classified into types:-

a) Shallow wells

b) Deep wells

a) Shallow wells.

A shallow well is the one which rest in pervious stratum draws its supply from the

surrounding materials.


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b) Deep well.

A deep well is the one which rests on an impervious “Mote” layer and draws its supply

from pervious formation lying below. The “Mote” layer (layer of clay, cemented sand or

other hard materials which often found laying a few meters below the water table in the

subsoil).

2. Tube wells

Here long pipes or tubes are bored or drilled deep into the ground, intercepting one or

two water bearing stratum.

11.5.2 Selection of a site for a well

The factors to be carefully studied before selecting a site for sinking a well are:-

1. Topography

2. Climate

3. vegetation

4. Geology of the area

5. Porosity, permeability and alteration of rocks.

6. Joints and faults in rock

7. Folded strata.

8. Proximity of any tank, river, spring, lake, unlined channels, reservoirs etc.

9. Existing wells in the vicinity.

11.6 Aquifers.

An aquifer may be defined as a formation of a permeable material, which is capable to

field appreciable quantities of ground water under gravity.

An aquifer is a body of saturated rock or sediment through which water can move easily.

Aquifers are both highly permeable and saturated with water. A well must be drilled into

an aquifer to reach an adequate supply of water. Good aquifers include sand stone,

conglomerate, well-jointed lime stone, bodies of sand and gravel and some fragmental

or fractured volcanic rocks such as columnar basalt. Crystalline rocks such as granite,

gabbros, gneiss, schist and some types of lime stone because they are not very porous,


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are considered not good aquifers. The porosity of such rocks may be 1% or less. Shale

and crystalline rocks are called aquitards because they retard the flow of ground water.

The geological formation or stratum of impervious material which does not admit ground

water is called an aquiclude. They usually contain and transmit small quantities of

water; examples are clay, mudstone, shale, and un-fractured igneous and metamorphic

rocks.

Other geological formations for example un-weathered granite, Dolerites and fresh

carbonate rocks that supposedly neither contain nor transmit water are known as

aquifuges. The importance of these formations is that they form boundaries of aquifers

and provide the clastic materials for formation of aquifers.

11.6.1 Types of Aquifers

Aquifers vary in depth, lateral extent and thickness but in general, all aquifers fall into

one of the two categories:-

1. Unconfined aquifers

2. Confined aquifers

Unconfined aquifers

Unconfined aquifers, also called non-artesian aquifers, are the top-most water bearing

strata having no confined impermeable over-burden rock bed lying over them. The

ordinary gravity wells of 2 to 5 m diameters, which are excavated through such top most

aquifers, are known as unconfined wells. The water level in these wells will stand equal

to the level of water table. Such wells are also known as water-table wells or gravity

wells.

Confined aquifers

When an aquifers is encased on its upper and under surface by impervious rock

formation (aquiclude), and is also broadly inclined so as to expose the aquifer

somewhere to the catchment area at a higher level for the creations of sufficient

hydraulic head, it is called a confined aquifer or an artesian aquifer. A confined aquifer

is completely filled with water under pressure, and which is usually separated from the

surface by a relatively impermeable confining bed; or aquitards, such as shale. An

unconfined aquifer is recharged rapidly by precipitations, has a rising and falling water


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table during wet and dry seasons, and has relatively rapid movement of ground water

through it. A confined aquifer is recharged slowly through confining shade beds. A well

excavated through such an aquifer yields water that often flows out automatically,

under hydrostatic pressure, and may even rise or gush out of surface for a reasonable

height. However, where the ground profile is high, the water may remain well below the

ground level. The former type of wells, where water is gushing out automatically, are

called flowing wells.

Perched aquifers

Perched aquifer is a special case which is sometimes found to occur within an

unconfined aquifer. If within the zone of saturation, an impervious deposit below a

pervious deposit is found to support a body of saturated material; then, this body of

saturated material which is a kind of an aquifer is known as the perched aquifer; the

top surface of the water held in the perched aquifer is known as the perched water table.


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11.7 Springs:

A spring is a place where water flows naturally from rock on to the land surface. The

natural outflow of ground water at the earth’s surface is said to form a spring.

A pervious layer sandwiched between two impervious layers gives rise to a natural

spring. A spring indicates the out cropping of the water table. Some springs discharge

where the water table intersects the land surface, but they also occur where water flows

out from caverns or along fractures, faults, or rock contacts that come to the surface.

Springs are generally capable of supplying very small amounts of water, and therefore

mostly not regarded as source of water supplies.

11.7.1 Formation and types of springs

Gravity springs

When the ground-water table rises high and the water overflows through the sides of

the natural valley or a depression, the spring formed is known as a gravity spring. The

flow from such a spring is variable with the rise or fall of water table.

Surface springs.

Sometimes, an impervious obstruction or stratum, supporting the underground storage,

becomes inclined, causing the water table to go up and get exposed to the ground

surface. This type of spring is known as a surface spring. The quantity of water available

from such a spring is quite uncertain.

Artesian spring

When the above storage is under pressure i.e. the water is flowing through some

confined aquifer, the spring formed is known as an artesian spring. These types of

springs are able to provide almost uniform quantity of water. Since the water oozes out

under pressure, they are able to provide higher yields, and may be thought of as the

possible sources of water supply.


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11.8 Isotropy and Anisotropy

11.8.1 Isotropy (KV = KL)

Aquiclude

KV

KL Confined Aquifer

Aquiclude

This is a phenomenon where the hydraulic conductive in the vertical directions KV will

be equal to hydraulic conductivity in horizontal direction KL.

11.8.2 Anisotropy (KL >>>>> KV)

This is a phenomenon, where the hydraulic conductivity in the horizontal directions KL,

will be significantly greater than its hydraulic conductivity in the vertical direction KV.

11.9 Potentiality of different Rocks as Aquifers

The various kinds of rocks possess variable water bearing properties, depending chiefly

on their permeability and porosity these include:-

1. Sedimentary rocks

2. Metamorphic rocks

3. Igneous rocks.

11.9.1 Sedimentary rocks as aquifers.

Sedimentary rocks generally constitute the best aquifers. Sedimentary rocks, such as

gravels possess the highest water-retaining as well as water yielding capacities this more

true in case of loose and weakly cemented course gravels. Next to gravel, the other

Sedimentary rocks in their successive order of decreasing water bearing capacity are:-

loose sands, sand stones, limestone, etc. shales (clays) are the poorest in absorbing

water, being impermeable although porous, and hence classified as aquiclude.

Amongst Sand stones, the water-bearing capacity depends much upon their texture and

nature of cementing material. Coarse-grained sandstones may be good aquifers, where


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as fine-grained sandstones may prove to be the poorest aquifers, with almost no possible

yield of water. The water bearing capacity of limestone depend much upon the presence

of solution channels, crevices, fissures, and other such openings in the rock. Hence

fissured and cracked lime stones may prove to be excellent aquifers and many other

compacted lime stones may prove to be totally unproductive.

11.9.2 Metamorphic Rocks as Aquifers.

Non-foliated metamorphic rocks like marbles and Quartzite are generally impermeable,

except along the original bedding, if the same is not completely destroyed during

metamorphism. These rocks, thus, normally behave as aquicludes. The foliated

metamorphic rocks like slates, schist, phyllites, and sometimes even gneisses, may

contain some good amount of ground-water due to their being highly fractured.

11.9.3 Igneous Rocks as Aquifers

The igneous rocks are generally the poorest aquifers.

The intrusive igneous rocks like Granites, Syenites, etc, are generally very compact and

dense, and hence are non-porous. They are, thus barren of groundwater under normal

conditions. However, when they are traversed by fissures or cracks, they may be capable

of holding some ground water quantities. Even these cracks and figures die out with

depth and as such, there is absolutely no possibility of getting any ground water in these

rocks at depths greater than 80 to 100 meters.

The extrusive igneous rocks also exhibit great variations in their water bearing

properties. Basic igneous rocks like Basalts are generally rich in cavities and

contraction cracks and as such may become permeable and sources of underground

water. Acidic igneous rocks like Rhyolites may or may not contain ground water,

because such rocks although generally possess interstices but may be filled up with ash

and other materials and become uncertain of containing water.

11.10 Groundwater Prospecting

The term ground-water prospecting means searching for the ground water. It does not

only include to find out the places where ground water is available, but also to find out

its approximate quantity and quality as well.

This job can be done by carrying out what is called ground-water surveys.


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11.10.1 Objectives of hydro-geological investigation

The objectives of any hydro-geological investigations are:-

1. To define recharge and discharge areas

2. Define major water bearing units.

3. Define location, extent and interrelationship of aquifers.

4. Establish physical parameters of aquifers like transmissibility, storage, coefficient

and specific field

5. Estimate total subsurface storage capacity

6. Establish geological factors which affect quality of ground water.

7. Arrival at the location, probable depth of drilling and field from the bore well, (tube

well)

8. To establish the level of water in the ground, their variation over an area and their

fluctuation with time.

11.10.2 Methods of exploration

A number of techniques can be used in combination to determine the location of ground

water. These may include

- Maps- topographic and geological

- Vegetation survey

- Local knowledge

- Remote sensing- aerial photos and satellite imagery

- Geophysics.

- Drilling

11.10.2.1 Desk study and initial survey

Reports and maps of various kinds are a useful starting point for ground water

exploration.

Topographic maps will indicate the nature of the terrain and the presence of any springs,

streams, or lakes. Geological maps will only give a general indication of the likely rock


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types and sometimes ignore the thin surface sediments which can be important local

sources of ground water. Valuable information can be obtained from a visit to the area

under consideration. The growth and occurrence particular types of vegetation often

indicates the presence of water these include the Baobabs trees of East Africa which

usually grow where the permanent water table is within rooting depth. Trees and

shrubs which thrive in distinct linear patterns during drought periods may indicate

fissures containing stored ground water. Local knowledge is of particular importance

and is generally best obtained by talking to people who live in the study area.

11.10.2.2 Remote sensing

The term remote sensing is used to describe all the techniques which collect information

from electromagnetic radiation reflected, emitted or transmitted from surface or near

surface features of the Earth. The Techniques range from simple aerial photographs to

oblique radar generated data collected by specially equipped aircraft. In most humid

and temperate locations remote sensing techniques will only be useful in helping to

provide information on the surface features that exist. The presence of groundwater

cannot be detected directly but only inferred from the information collected on surface

geology, soil moisture, vegetation and groundwater discharge.

11.10.2.3 Geo-physics

Geophysics may be used to supplement surface data by providing information on the

sub-surface properties of the ground.

These properties can give useful indications of the presence or otherwise of ground

water. The geophysical techniques that are most appropriate to groundwater exploration

are:


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1. Resistivity: This uses the direct contact of electrodes placed into the ground to

measure the resistance to electricity. Water is a better conductor of electricity than

the rock; hence water bearing strata will have a lower resistivity than similar strata

that are dry

2. Conductivity: This is a non-contact method uses electro-magnetic principles

determine the ease with which electricity passes through the ground. It can be used

to locate gravel, shallow bedrock, Saline intrusions and cavities in carbonate rock (e.g.

lime stone)

3. Seismic refraction: This technique depends on rocks with different densities

transmitting sounds or vibrations at different velocities and can be used to locate

boundaries between subsurface layers and the depth to the water table.

11.10.2.4 Drilling

Drilling is generally the final stage in exploration. It is the only way to confirm the

presence of ground water beyond all doubt and gives vital information regarding

geological conditions and the hydraulic characteristics of potential aquifers. There are

many techniques available. Selection of an appropriate method will depend on a

number of factors including the type of rocks to be penetrated the likely depth to the

water table and the availability of equipment.

11.10.3 Logs or recording of Bore-hole Data

Logs may be defined as the recodes of the sub-surface investigations and provide useful

information regarding the nature and properties of the materials occurring at various

depth below the ground surface.

These records may be in the form of more tables or graphic plots with symbolic

descriptions. The data making the basis of these records may be obtained by different

method and accordingly these are many types of bore-hole logs; like geological logs

which are representing the geological type of the strata occurring at different depths and

encountered during direct digging or boring of wells.


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PAST PAPERS


2010/2011.




HIGHER DIPLOMA IN CIVIL AND BUILDING ENGINEERING - I

SEMESTER I TEST ONE 2008/2009

DCE 312: ENGINEERING GEOLOGY

Date: Thursday 18th – September - 2008 Time: 7:15pm – 8:15pm

INSTRUCTIONS:

This test contains questions from two (2) chapters.

Attempt all questions.

All questions carry marks indicated.

a) Briefly describe the scope of Geology (5 marks)

b) Differentiate between Geology and Engineering Geology (2 marks)

c) Why do you study Geology? (5 marks)

d) Discuss what you know about the internal constitution of the Earth (9 marks)

e) Briefly explain the last three (3) eras of Geologic time scale (6 marks)

f) What is continental drift and clearly show the evidences supporting it (5 marks)

g) What is Geologic time? (1 mark)

h) Differentiate between Plate Tectonics and Sea-floor spreading (4 marks)

i) Which category of scientist is responsible for determining the age of the Earth (1 mark)

j) Mention any technique used by these Scientists in (i) above to determine the age of the

Earth (1 mark)

k) What is the estimated age of the Planet Earth? (1 mark)


2010/2011.





SEMESTER I TEST TWO 2008/2009


Date: Friday 17th - October - 2008 Time: 7:05pm – 8:35pm

INSTRUCTIONS:

This test contains questions from Three (3) chapters.


All questions carry marks indicated.

1. Briefly discuss any five (5) physical properties of minerals. (5 Marks)

2. Mention any ten (10) minerals and their respective uses found in the various

districts of the Republic of Uganda. (5 Marks)

3. Describe how you can prepare a rock slide; also instrument and process involved in

optical mineralogy. (8 Marks)

4. With illustrations, discuss the Rock Cycle. (5 Marks)

5. With illustrations and examples where possible, discuss the mode of occurrence of

igneous rocks. (8 Marks)

6. Discuss the formation of Sedimentary rocks. (7 Marks)

7. Differentiate between metamorphic rocks and metamorphism (2 Marks)

8. With examples and illustrations, briefly discuss folds, joints, and faults. (10 Marks)


2010/2011.


KYAMBOGO UNIVERSITY



ORDINARY DIPLOMA IN WATER ENGINEERING

YEAR I SEMESTER II EXAMINATIONS 2007/2008

DWE 123: GEOLOGY AND SOILS

Date: Wednesday 20th – August – 2008 Time: 8:00Am – 11:00Am

INSTRUCTIONS:

This Examination paper contains Eight (8) questions.

Attempt any Five (5) questions.

All questions carry equal marks.

Begin each question on a fresh page.

Do not write anything on the question paper, all rough work should be done on the official

answer booklet.

Question One

a) Differentiate between intrusive and extrusive rocks. (4 marks)

b) What is a mineral? (1 mark)

c) Briefly describe the layers of Planet Earth. (9marks)

d) Explain the three (3) types of rocks you know giving two (2) examples of each. (6 marks)

Question Two

a) Differentiate between petrology and mineralogy (2 marks)

b) With illustrations where necessary, explain the following terms:-

i. Batholith,

ii. Laccolith,

iii. Lava flows,

iv. Dykes, (8 marks)

c) Differentiate between weathering and erosion (2 marks)

d) Briefly describe the four (4) stages of sedimentary rock formation. (8 marks)


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Question Three

a) Mention any five (5) minerals found in Uganda and their respective uses. (5 marks)

b) What is Site Investigation? (1 mark)

c) A polarizing microscope is the most important instrument which is used in any study dealing with the

process of determining the optical properties of minerals.

Give any five (5) of its essential parts. (5marks)

d) Draw well labeled structural representations of the following: -

i. Reverse fault,

ii. Anticline,

iii. Syncline (9 marks)

Question Four

a) Define Geology. (1 mark)

b) What do you understand by the term “Site Reconnaissance”? (2 marks)

c) Briefly explain the sources of information in the Desk Study. (5 marks)

d) With the aid of a drawing/sketch describe the rock cycle. (6 marks)

e) What do you understand by Continental Drift, Sea- floor spreading and Plate Tectonic? (6 marks)

Question Five

a) Define Paleozoic era, Mesozoic era, and Cenezoic era. (3 marks)

b) Differentiate between lithosphere and asthenosphere by use of a sketch (5 marks)

c) With illustrations explain the following types of folds: -

i. Open Folds,

ii. Isoclined Fold,

iii. Overturned fold,

iv. Recumbent fold (12 marks)

Question Six

a) With illustrations, explain the following fault terminologies: -

i. Strike of the fault,

ii. Dip of the fault,

iii. Hade (6 marks)

b) Mention about three (3) agents of soil erosion (3 marks)

c) What do you understand by a rock? (1 mark)

d) Briefly describe any five (5) physical properties of minerals (10 marks)


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Question Seven

a) Explain the term Representative sample and its methods. (4 marks)

b) Define Specific gravity of the soil. (2 marks)

c) How is Specific gravity of soil determined in the Laboratory, using Density Bottle method? (8 marks)

d) What do you understand by the term moisture content of the soil? (2 marks)

e) Using Specific gravity practical results of the soil given, calculate the Specific gravity value. (4 marks)

Mass of density bottle = 115g

Mass of density bottle containing dry soil = 165g

Mass of density bottle containing saturated soil = 261g

Mass of density bottle containing liquid only = 230.5g

Question Eight

a) What do you understand by the term particle size distribution of soil? (2 marks)

b) How is particle size distribution of soil determined, using dry sieving method? (8 marks)

c) On 27th/June/2008, students of ordinary diploma in Water Engineering, year one, group A; carried

out a particle size distribution practical on soil sample in the DCBE Materials Testing Laboratory and

got the following results:-

Sieve sizes (mm)

Weight Retained (g)

10 0

6.3 42

5 105

2 115.5

1.18 136.5

0.6 84

0.425 94.5

0.3 136.5

0.212 115.5

0.15 52.5

0.063 84

Receiver 84

i. Calculate the percentage passing each sieve size. (5 marks)

ii. Plot the grading curve (3 marks)

iii. Make conclusion basing on (ii) above (2 marks)


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Name: …………………………………………………………………………………………………………………………………

Reg. No.: …………………………………………………………………………………………………………………………….

Program: ……………………………………………………………………………………………………………………………..

Date: ……………………………………….

PARTICLE SIZE DISTRIBUTION CHART


2010/2011.


KYAMBOGO UNIVERSITY




SEMESTER I, TEST ONE, 2009/2010


Date: Friday 2nd – October - 2009 Time: 7:15pm – 8:45pm

INSTRUCTIONS:

This test contains questions from three (3) chapters.


All questions carry marks as indicated.

a) Differentiate between Geology and Engineering Geology. (2 marks)

b) Describe the scope of geology. (5 marks)

c) Why do you study Geology? (5 marks)

d) What is the estimated age of the earth; and what name is given to people

responsible for determining its age? (2 marks)

e) Describe fully the internal constitution of the earth. (6 marks)

f) Differentiate between Plate Tectonics and Continental drift. (2 marks)

g) Give concrete evidences supporting continental drift. (4 marks)

h) What do you understand by sea floor spreading? (2 marks)

i) List any three (3) Eons of the geologic time scale. (3 marks)

j) Describe any three (3) Eras of one of the above Eons. (6 marks)

k) Differentiate between mineralogy and minerals. (2 marks)


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l) List any ten (10) minerals with their respective uses found in the Republic of

Uganda. (5 marks)

m) Explain any four (4) physical properties of minerals. (8 marks)

n) Explain any four (4) microscopic optical properties of minerals. (8 marks)

KYAMBOGO UNIVERSITY




SEMESTER I, TEST ONE, 2009/2010


Date: Friday 6th – November - 2009 Time: 7:15pm – 8:45pm

INSTRUCTIONS:

This test contains questions from four (4) chapters.


All questions carry marks as indicated.

1) Explain the causes of folding. (4 marks)

2) Explain folds, faults and joints as applied in structural geology. (6 marks)

3) Discuss the Civil Engineering considerations involved in dealing with folded, faulted

and jointed rocks. (9 marks)

4) Describe the rock cycle. (5 marks)

5) Explain the mode of occurrence of igneous rocks. (7 marks)


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6) Explain the formation and classification of sedimentary rocks. (12 marks)

7) Explain the types of seismic waves. (6 marks)

8) The site investigation report is the final product of the exploration program. If you

are given a task to prepare one, which important information would you include

while preparing one? (6 marks)

9) Explain the sources of information in a desk study during site investigation.(5

marks)

DID YOU KNOW THIS?

From BODY, Editorial Consultant, Robert Winton.

Weight for weight, Bone is six times stronger than steel.

What makes a genius a genius? This was the question that motivated Dr. Thomas

Harvey to remove the brain of the physicist Albert Einstein (1879 - 1995) when he

died. Harvey sliced Einstein’s brain into 240 pieces. Later, research suggested that

although Einstein’s brain weighed less than average, there were more neurons

packed into the cerebral cortex (grey matter). They also found unusual grooves in

the part of the brain – the parletal lobe – that deals with mathematical reasoning.

Your tongue does more than just detect sweet, sour, salty, and bitter tastes. It has

pain detectors (nociceptors) that are stimulated by capsaiein, a substance released

by hot chili peppers. So, the hot feeling you get from chilies is actually pain! Your

tongue also has touch receptors that tell whether the food you are chewing is smooth

or rough. Heat detectors (thermo-receptors) register the difference between cold ice

cream and hot baked potato. All these receptors help to make your food more – or

less – enjoyable.

The eye can detect up to 10 million different colours.


2010/2011.


Your nose can detect more than 10,000 smells.

Your Brain is more complex than any computer.

Salivary Gland pour about one (1) liter of saliva into your mouth daily.

Why do valentine cards have hearts on them? Why do people talk about “having a

broken heart”? This is because long ago people thought that the heart was the organ

of love and emotion. This belief has persisted to the present day, even though we

now know it is our brain that is responsible for these feelings.

Your shoulder joint is the most flexible joint in your entire body.

In 1543, the first accurate study of human anatomy appeared when Andreas

Vesalius (1514 - 64) – a Belgian doctor based in Padua, Italy – published a book

called on the structure of the Human Body, which was filled with amazing drawings

of dissected (cut-up) bodies. In his younger days, Vesalius stole the bodies of hanged

criminals to make his dissections. But once he became famous, the town of Padua

readily supplied him with corpses to dissect.

The pelvis keeps your body balanced over your legs.


2010/2011.


BIBLIOGRAPHY

A. KOMAR. Building Materials and Components

F.G.H. BLYTH & M.H. de FREITAS. Geology for Engineers, Seventh Edition

KATTO EDWARDS, 2002 Summarized Uganda Mineral Inventory and their uses

MICROSOFT CORPORATION, Encarta Encyclopedia

PLUMMER, MC GEARY AND CARLSON, Physical Geology, ninth edition

ROBERT F. LEGGET. Geology & Engineering

ROBERT WINTON, BODY, Editorial Consultant.

S. K. GARG, Physical and Engineering Geology

Geologists should approve Building plans; New Vision Article October 2008

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