session 7 soil stabilization

8/10/2019 Session 7 Soil Stabilization

1/67

The soil stabilization means the improvement of stability or bearing power of the soil by

the use of controlled compaction, proportioning and/or the addition of suitable admixture or

stabilizers.

Basic Principles of Soil Stabilization.

Evaluating the properties of given soil

Deciding the lacking property of soil and choose

effective and economical method of soil stabilization

Designing the Stabilized soil mix for intended

stability and durability values


2/67

Limited Financial Resources to Provide a complete

network Road System to build in conventional

method

Effective utilization of locally available soils and

other suitable stabilizing agents.

Encouraging the use of Industrial Wastages in

building low cost construction of roads.


3/67

Mechanical Stabilization

Soil Cement Stabilization

Soil Lime Stabilization

Soil Bitumen Stabilization

Lime Fly ash Stabilization

Lime Fly ash Bound Macadam.


4/67

This method is suitable for low volume roads i.e.

Village roads in low rainfall areas.

This method involves the correctly proportioning

of aggregates and soil, adequately compacted to

get mechanically stable layer

The Basic Principles of Mechanical Stabilization

are Correct Proportioning and Effective

Compaction


5/67

Adequate Strength

Incompressibility

Less Changes in Volume

Stability with Variation in water content

Good drainage, less frost Susceptibility

Ease of Compaction.


6/67

Mechanical Strength of aggregates

Gradation

Properties of the Soil

Presence of Salts

Compaction


7/67

Mechanical Strength

When the soil is used in small proportion to fill

up the voids the crushing strength of aggregates

is important

Gradation

A well graded aggregate soil mix results in a mix

with high dry density and stability values

Properties of soil

A mix with Plasticity Index, results poor stability

under soaking conditions. Hence it is desirable tolimit the plasticity index of the soil


8/67

Presence of Chemicals

Presence of Salts like Sulphates and mica

are undesirable

Presence of Calcium Chloride is BeneficialCompaction

Effective Compaction is desirable to

produce high density and stability mix


9/67

Soil Cement is an intimate mix of soil, cement

and water, compacted to form a strong base

course

Cement treated or cement modified soil refers to

the compacted mix when cement is used in

small proportions to impart some strength

Soil Cement can be used as a sub-base or base

course for all types of Pavements


10/67

Soil

Cement

Pulverisation and Mixing

Compaction

Curing Additives


11/67

Soil

THE PHYSICAL PROPERTIES

Particle Size Distribution

Clay content

Specific Surface

Liquid limit and Plasticity Index

Cement

A increase in cement content generally causes

increase in strength anddurability


12/67

Pulverisation and Mixing

Better the Pulverisation and degree of mixing,

higher is the strength

Presence of un pulverised dry lumps reduces

the strength

Compaction

By increasing the amount of compaction dry

density of the mix, strength and durabilityalso increases


13/67

Curing

Adequate Moisture content is to be retained in

order to accelerate the strengthAdditives

There are some additives to improve properties

Lime

Sodium hydroxide

Sodium Carbonate Calcium Chloride


14/67

Soil Cement specimens are prepared with

various cement contents in constant volumes

moulds

The compressive strength of these specimens

tested after 7 days of curing

A graph is plotted Cement content Vs

compressive strength

The Cement Content Corresponding to a

strength of 17.5 kg/cm2 is taken as design

cement content


15/67

Soil- Lime has been widely used as a

modifier or a binder

Soil-Limeis used as modifier in high plasticity

soils

Soil Lime also imparts some binding action

even in granular soils


16/67

Soil-Lime is effectively used in Expansive

soils with high plasticity index.


17/67

Lime Content

Generally increase in lime content causes

slight change in liquid limit and considerable

increase in Plasticity index

The rate of increase is first rapid and then

decreases beyond a certain limit

The point is often termed as lime fixationpoint

This is considered as design lime content


18/67

Type of Lime

After long curing periods all types of limes produce

same effects. However quick lime has been foundmore effective than hydrated lime

Calcium Carbonate must be heated at highertemperature to form Quick lime calcium oxide( CaO)

Calcium oxide must be slaked ( by the addition ofwater) to form Hydrated lime

Compaction Compaction is done at OMC and maximum dry

density.


19/67

Curing

The strength of soil-lime increases with curing

period upto several years. The rate of

increase is rapid during initial period

The humidity of the surroundings also affects

the strength

Additives

Sodium metasilicate, Sodium hydroxide and

Sodium Sulphate are also found useful

additives


20/67

The Basic Principles of this stabilization are

Water Proofing and Binding

By Water Proofing inherent strength and

other properties could be retained

Most Commonly used materials are Cutback

and Emulsion

Bitumen Stabilized layer may be used as

Sub-base or base course for all the roads


21/67

Soil

The particle size, shape and gradation of the

soil influence the properties of the soil-bitume

mix.Types of Bitumen

Cutbacks of higher grade should be preferred

Emulsions generally gives slightly inferiorresults than Cutback.


22/67

Amount of Mixing

Increasing proportion of bitumen causes a

decrease in dry density but increases the

stability after a certain bitumen content

The optimum bitumen content for maximum

stability generally ranges from 4 to 6%Mixing

Improved type of mixing with low mixing period

may be preferred


23/67

Compaction

Effective Compaction results higher

stability and resistance to absorb waterAdditives

Anti stripping and reactive chemical additives have been tried to improve

the properties of the mixes

Portland cement can also be used along with the soil bitumen


24/67

Scarcity of good quality aggregates / soil for

road construction

Production and accumulation of different

waste materials

Disposal and environmental problem

Economical and gainful utilisation


25/67

Quality of waste is not controlled by theirmanufacturers

Characteristics of by-products vary in a widerange

Road construction practice is accustomed totraditional materials of steady quality

Specifications of layers compaction of traditionalmaterials are not suitable for waste materials


26/67

Amount of yearly produced waste materialshould reach a certain lower limit

The hauling distance should be acceptable

The material should not have a poissonous effect The material should be insoluble in water

The utilisation should not have a pollutionaleffect to the environment


27/67

Free from organic matter

Should not swell or decay as influenced by water

Should not be soluble in water

Particles should be moderately porous


28/67

Thermal Power Stations* Fly ash

* Bottom ash

* Pond ash

Steel Plants* Blast furnace slag

* Granulated blast furnace slag

* Steel slag


29/67

Thermal power - Major role in powergeneration

Indian scenario - Use of coal with highash content

- Negligible utilisationof ash produced

Bulk utilisation - Civil engineeringapplications like

construction of roads &embankments


30/67

n Can be used for construction ofn Embankments and backfillsn Stabilisation of subgrade and sub-base

n Rigid and semi-rigid pavements

n Fly ash properties vary widely, to be characterised

before use

n Major constituents - oxides of silica, aluminum,iron, calcium & magnesium

n Environmentally safe material for roadconstruction

n Possesses many favourable properties forembankment & road construction

Utilisation of fly ash


31/67


32/67

Parameter Range

Specific Gravity 1.90 2.55

Plasticity Non plastic

Maximum dry density (gm/cc) 0.9 1.6

Optimum moisture content (%) 38.0 18.0

Cohesion (kN/m2) Negligible

Angle of internal friction (j) 300 400

Coefficient of consolidation Cv (cm2/sec) 1.75 x 10

-52.01 x10-3

Compression index Cc 0.05 0.4

Permeability (cm/sec) 8 x 10-67 x 10-4

Particle size distribution (% of materials)Clay size fraction

Silt size fraction

Sand size fraction

Gravel size fraction

1 10

8 85

7 90

0 10

Coefficient of uniformity 3.1 10.7


33/67


34/67

Ideally suited as backfill material for urban/ industrial areas andareas with weak sub soils

Higher shear strength leads to greater stability

Design is similar to earth embankments

Intermediate soil layers for ease of construction and to provideconfinement

Side slope erosion needs to be controlled by providing soil cover

Can be compacted under inclement weather conditions

15 to 20 per cent savings in construction cost depending on leaddistance


35/67

Earth

CoverEarth

Cover

Bottom ash or

Pond ash

Typical cross section of fly ash road embankment


36/67

Approach embankment for second Nizamuddinbridge at Delhi

Length of embankment - 1.8 km

Height varies from 6 to 9 m

Ash utilised - 1,50,000 cubic metre

Embankment opened to traffic in 1998

Instrumentation installed in the embankment

showed very good performance

Approximate savings due to usage of fly ash is

about Rs.1.00 Crore


37/67

Approach embankment for second Nizamuddinbridge at Delhi


38/67

Spreading of pond ash

Compaction of pond ash

Second Nizamuddin bridge approach embankment


39/67

Stone pitching for slope

protection

Traffic plying on the

embankment

Second Nizamuddin bridge approach embankment


40/67

Water logged area

(soft ground conditions)

Compaction of fly ash over layer of geotextile

Length of stretch

54 km

Height of embankment 3 to

4 m

Fly ash utilisation 2 Million

cubic metres


41/67

Fly ash - better backfill material for reinforcedembankments

Polymeric reinforcing materials Geogrids,

friction ties, geotextiles Construction sequence similar to reinforced

earth structures


42/67

Pond AshFill

7.8 to

5.9 m

Facing

panels

Filter

medium Geogrids

Reinforced foundation mattress of bottom ash

Okhla flyover approach embankment


43/67


Erection of facing panels

Rolling of pond ash


44/67

Support provided to facing

panels during construction

Laying of geogrids



45/67

Geogrid reinforced fly ash approach embankment

Length of embankment

138.4 m Height varied from 3.42 m to 1.0 m

Opened to traffic in 1997


46/67

Sarita Vihar flyover reinforced approach embankment

Arrangement of frictionties before laying pond ash

Laying of friction ties


47/67

Compaction using platevibrator near the facing

panels

Compaction of pond ash

using static and vibratory

rollers

Sarita Vihar flyover reinforced approach embankment


48/67

Stabilised soil subgrade & sub-base/base courses

Mixing with soil reduces plasticity characteristics ofsubgrade

Addition of small percentage of lime or cement greatlyimproves strength

Leaching of lime is inhibited and durability improves due to

addition of fly ash Pond ash & bottom ash can also be stabilised

Lime-fly ash mixture is better alternative to moorum forconstruction of WBM / WMM


49/67

Construction of semi-rigid/ rigid pavements

Lime-fly ash concrete

Dry lean cement fly ash concrete

Roller compacted concrete

Fly ash admixed concrete pavements

Lime-fly ash bound macadam

Precast block paving

High performance concrete

Fly ash for road construction


50/67

WBM Gr II/WMM 150 mm

WBM Gr III/WMM 75 mm

GSB 350 mm

BM 75 mm

DBM 100 mm

Bituminous concrete 40 mm

Typical cross section of flexible pavement conventionalsection


51/67

Fly ash + 6% cement stabilised layer

150 mm

Typical cross section of flexible pavementusing fly ash

WBM Gr III/WMM 75 mm

Pond ash 350 mm

BM 75 mm

DBM 100 mm

Bituminous concrete 40 mm


52/67

Pond ash 300 mm

DLFC 100 mm

Fly ash admixed PQC 300 mm

Typical cross section of rigid pavement using fly ash


53/67

Mixing of lime stabilised

pond ash

Compaction of stabilised

pond ash using road roller

Demonstration road project using fly ash at Raichur


54/67

Construction of roller

compacted concretepavement

View of the demonstrationroad stretch after three years

Demonstration road project using fly ash at Raichur


55/67

Bottom ash

RCCP wearing course - 0.1 m

Stabilised fly ash

base - 0.1 mStabilised fly ash

Shoulder

Soil cover

Demonstration road project using fly ash near Dadri

(U.P) Typical section


56/67

Stabilised base course

Compaction of RCCPMixing & laying of RCCP

Demonstration road

project using fly ash

near Dadri (U.P)


57/67

Guidelines available on pavement construction

IRC 60Tentative guidelines for use of lime fly ash concrete

as pavement base or sub-base

IRC 68 Tentative guidelines on cement fly ash concrete for

rigid pavement construction

IRC 74 Tentative guidelines for lean cement concrete andlean cement fly ash concrete as a pavement base or sub-

base

IRC 88 Recommended practice for lime fly ash stabilised soil

as base or sub-base in pavement construction


58/67

Published recently by Indian Roads Congress (SP-58:2001)

Includes design aspects also

Handling and construction

Loose layer thickness of 400 mm can be adopted ifvibratory rollers are used

Moisture content - OMC + 2 per cent

Use of vibratory rollers advocated

Minimum dry density to be achieved - 95 per cent ofmodified Proctor density

Ash layer and side soil cover to be constructedsimultaneously


59/67

Total production of slag from steel industries isabout 8.0 million tonnes

Types of slags

Blast furnace slag Granulated blast furnace slag (GBFS)

Air cooled slag

Steel slag

Granulated blast furnace slag


60/67

g

Contains reactive silica

Suitable for lime / cement

stabilisation

Air cooled blast furnace slag

Non

reactiveSuitable for use as

coarse aggregates


61/67

Characterization of slags produced at different steel

plants

Laboratory studies on Lime-GBFS mixes

Semi-field studies on Lime-GBFS concrete

Test track studies on usage of slags in road works


62/67

Property Durgapur Bhilai Rourkela DelhiQuartzite

Specificationrequirements

Specific

gravity

2.78

2.82

2.82

3.33

2.97

2.99

2.67 -

Waterabsorption(%)

1.53 1.72

0.58 1.38

0.74 1.29

0.48 2% Max

Los

Angelesabrasionvalue (%)

18.80 25.00 14.28 34.00 40% Max

Impactvalue (%)

15.79 14.80 16.90 24.50 30% Max

Soundnessvalue (%) 1.66 1.17 0.33 0.17 12% Max

Percentagevoids

46.40 43.90 43.10 43.80 -


63/67

Obtained as a waste product during productionof steel

Particle size varies from 80 mm to 300 microns

Compared to blast furnace slag, steel slagcontains lower amount of silica, higheramounts of iron oxide and calcium oxide

Due to presence of free lime, steel slag should

be weathered before using it in construction


64/67

Plant roads at Visakhapatnam

Test tracks in collaboration with AP PWD using slags

from Visakhapatnam Steel Plant

Test tracks in collaboration with Orissa PWD usingslags from Rourkella Plant

Test tracks at R&D Centre for Iron & Steel, Ranchi

using Slags from Bokaro Plant


65/67

Construction of

test track using

slag at Orissa

Labour based techniques for

construction of stabilised

layer

Li


66/67

View of finishedsurface of road

constructed using

slags at Orissa

Lime

stabilisation of

iron slags

(Orissa)


67/67

Processed municipal wastes

utilised for construction of test

track on village road near Delhi Stabilised municipal waste used

for construction of sub-base layer

Performance of stretch is good

session 7 soil stabilization

Documents