geotechnical laboratory manual

8/11/2019 Geotechnical Laboratory Manual

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CVEN365 Introduction to Geotechnical EngineeringLABORATORY MANUAL

Giovanna Biscontin

Texas A&M University

August 27, 2012


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2 CVEN365 Laboratory Manual

G. Biscontin Civil Engineering Department


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Contents

1 Laboratory Safety and Policy 1

2 Determining Water Content of Soil Specimens 3

2.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Water Content by Microwave Oven Method . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2.1 Standard Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2.2 Required Materials and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2.3 Test Specimen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2.4 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2.5 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.3 Water Content by Oven Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.3.1 Standard Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.3.2 Required Materials and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.3.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.3.4 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 Particle Size Analysis of Soils 9

3.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2 Standard Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Particle size analysis of coarse grained fraction . . . . . . . . . . . . . . . . . . . . . . . . 9


3.3.2 Test Sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.3.4 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.4 Particle size analysis of fine grained fraction . . . . . . . . . . . . . . . . . . . . . . . . . . 11


3.4.2 Hydrometer Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.4.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.4.4 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.5 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4 Atterberg Limits: Liquid Limit, Plastic Limit, and Plasticity Index of Soils 19

4.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19


4.3 Determination of Liquid Limit (Multi-Point Method) . . . . . . . . . . . . . . . . . . . . . 19


4.3.2 Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.3.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20


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4.3.4 Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.4 Determination of Plastic Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22


4.4.2 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.5 Plasticity Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5 Liquid Limit of Soils using the Drop Cone Penetrometer 25

5.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25


5.3 Determination of Liquid Limit Using Drop Cone Penetrometer . . . . . . . . . . . . . . . . 25


5.3.2 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5.3.3 Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6 Classification According to USCS 29

6.1 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.2 Initial Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.2.1 Highly Organic Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296.2.2 Non Highly Organic Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

6.3 Procedure for Classification of Fine Grained Soils . . . . . . . . . . . . . . . . . . . . . . 30

6.4 Procedure for Classification of Coarse Grained Soils . . . . . . . . . . . . . . . . . . . . . 31

7 Visual Classification of Soils 33

7.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33


7.3 Terminology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

7.4 Descriptive Information for Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

7.5 Procedure for Identifying Fine-Grained Soils . . . . . . . . . . . . . . . . . . . . . . . . . 35

7.6 Identification of Inorganic Fine-Grained Soils . . . . . . . . . . . . . . . . . . . . . . . . . 367.7 Procedure for identifying Coarse-Grained Soils . . . . . . . . . . . . . . . . . . . . . . . . 37

7.8 Check List For Description Of Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

8 Compaction Using Standard Effort 41

8.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41


8.3 Required Materials and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

8.4 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

8.4.1 Specimen preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

8.4.2 Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

8.5 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

9 Measuring Suction with the Filter Paper Method 47

9.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

9.2 Soil Suction Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

9.3 Required Materials and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

9.4 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

9.5 Soil Matric Suction Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

9.6 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

9.7 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51



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iv CVEN365 Laboratory Manual

15 One-Dimensional Consolidation 87

15.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87



15.3 Preliminary Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

15.3.1 The consolidometer and the dial gauge . . . . . . . . . . . . . . . . . . . . . . . . 8915.3.2 The data acquisition software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

15.3.3 The remaining preliminary details . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

15.4 Specimen Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

15.5 Procedure for pneumatic load frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

15.6 Procedure for mechanical load frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

15.7 Second and following days . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

15.8 Last day . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

15.9 Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

15.10Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

16 Triaxial Unconfined Compression Test 101

16.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10116.2 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

16.2.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

16.2.2 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

16.3 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

16.4 Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

17 Unconsolidated Undrained Triaxial Test 105

17.1 Specimen preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

17.1.1 Preparation of the specimen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

17.1.2 Fitting end caps and membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

17.2 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10617.3 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

17.4 Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

18 Triaxial Consolidated Drained Compression Test 109

18.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

18.2 Summary of Test Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

18.2.1 Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

18.2.2 Specimen Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

18.2.3 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

18.3 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

18.4 Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111



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Chapter 1

Laboratory Safety and Policy

Safety is a priority at Texas A&M University!

While it may seem unlikely that an accident could happen to you, you should know the accident rate in

universities is 10 to 100 times greater than in the chemical industry. To help prevent accidents, safety notes

are included in the laboratory manual. In addition, relevant Material Safety Data Sheets (MSDS) are in a

laboratory binder and guidelines are posted. Pay close attention to this information - our goals are to avoid

accidents in the laboratory, and to respond promptly and appropriately should an accident occur.

Safety depends on you!

It is your responsibility to follow the instructions in the lab manual and any additional guidelines provided

by your instructor. It is also your responsibility to be familiar with the location and operation of safety

equipment such as eyewash units, showers, fire extinguishers, chemical spill cleanup kits etc. Questions

about chemicals can be answered by referring to the appropriate Material Safety Data Sheet. If you need

help deciphering an MSDS, please see your instructor.

Safety is a primary concern in all of the Zachry Department of Civil Engineering Geotechnical Engineer-

ing laboratories. Both the Undergraduate laboratory (CVLB 117) and Graduate laboratory (CVLB 116D) are

outfitted with equipment that could cause injury if one is not alert while performing experiments. Following

is an outline of general policy and Dos and Donts in these laboratories. Safety is everyones concern.

1. No food or drink is allowed in the laboratories.

2. Wear appropriate protective clothing. You will not be allowed in the lab if you are wearing open-

toe shoes and/or shorts. Avoid shirts with dangling sleeves. Tie back long hair and avoid dangling

jewelry.

3. No phone calls and no text messaging in the laboratory. Set your cell phones to silent mode.

4. Ovens:

The large ovens in both rooms are set at 105 degrees C. Use properly insulated gloves to handleobjects you are retrieving out of the oven. The gloves are placed near the oven for this purpose.

Please return the gloves to the table by the oven.

The microwave ovens are used for moisture determination in SOILS ONLY. Never place morethan ONE soil sample at a time (in its aluminum dish) in a microwave oven during this process.

Check that a heat sink (in the form of a ceramic bowl) is in the microwave to avoid explosions.

5. There are two fire extinguishers in the Undergraduate laboratory and one extinguisher in the Graduate

laboratory. Please observe the mounting locations on the walls and make a mental note of their access.


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6. Safety glasses are in a large white cabinet on the north wall of the Undergraduate Laboratory. Should

you need to use a hammer or blunt instrument to break up dried soil samples, then all members of the

laboratory group will be required to wear safety glasses during this process, including the teaching

assistant.

7. Each laboratory island has a sink with two faucets. One faucet provides hot and cold tap water and is

used for cleanup only. The other faucet has a white button on it and is labeled DW (distilled water).

8. During some sessions noise from machinery (such as sieve shakers) may get loud. If this becomes

a problem, please notify the teaching assistant and ear protection will be provided on an as-needed

individual basis.

9. Barrels are provided for used soil when the experiment is completed. Never throw trash (foil cups,

paper, plastic, etc.) in these barrels. There are trash bins provided for garbage.

10. At the end of each laboratory session always clean all the instruments and other materials used. A

paper towel dispenser hangs on the wall for cleanup.

11. Counterbalanced Load Frames:

There are four double load frames in the Undergraduate laboratory and two double load framesin the Graduate laboratory. These frames are safe to operate when using the correct procedure.

Never touch these frames when not in use.

When using the loading frames:

Never have your head under the top counterweight. The weight may fall while making

adjustments to the set up. This typically occurs at least once a semester. You want to make

sure the weight does not fall on you, and especially your head.

You are required to complete and sign (accept) aStudent Safety Contract Agreement(LSA) on Howdy

before the first laboratory class in order to be allowed to participate in the laboratory activities. Inaddition, you will have to pass a quiz on safety procedures in the geotechnical laboratories based on

the information in this chapter. Questions about safety will also be included in quizzes administered

at teh beginning of other laboratory sessions during the semester.



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Chapter 2

Determining Water Content of Soil

Specimens

2.1 Purpose

The water (or moisture) content of a soil is recorded in every test in geotechnical engineering. This basic

type of information provides insight on the conditions of the soil. The water content of undisturbed samples

from the site is also measured and reported on boring logs and in the engineering reports. Sometimes, we

need to mix a soil to a certain water content to meet specifications for construction.

Traditionally, we used a standard oven set at a temperature of 110oC. These days we can also use a

microwave oven, which gives immediate results. The two methods are only slightly different and they are

both explained in this chapter. You will mostly use the microwave oven method, but in a few cases the

standard method is more reliable. The instructions for the specific test will tell you which method to use for

each laboratory experiment.

2.2 Water Content by Microwave Oven Method

This method is commonly used as a quicker alternative to the standard oven drying method, therefore it is

mostly used when immediate results are needed. You cannot use the microwave oven method for soils with

significant levels of organics.

The main problem with using the microwave oven for water content determination is the possibility

of heating the soil to temperatures higher than 110o C. The higher temperature may actually change the

chemical structure of the clay minerals (think about pottery) and give wrong results. By drying the soil in

several steps you minimize the chance of overheating.

2.2.1 Standard Reference

ASTM D 4643- Standard test method for determination of water (moisture) content of soil by the microwave

oven heating.

2.2.2 Required Materials and Equipment

The following items will be required for this testing method:

A microwave oven. Variable power controls are important and reduce the potential for overheating thetest specimen.


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2. Determining Water Content of Soil Specimens 5

2.2.5 Calculations

Calculate the Water content of the sample as follows:

w=Mcws Mcs

Mcs Mc 100 =

MwMs

100 (2.1)

where:

w = water content, %

Mcws = mass of container and wet specimen, g

Mcs= mass of container and oven dry specimen, g

Mc= mass of container, g

Mw = mass of water, g and

Ms= mass of solid particles.

Moisture Content Determination by Microwave Oven

Sample No. B-24 Project

Boring No. 12-L Location

Depth 2.4 m

Description of sample Brown silty clay

Date 09/05/03 Tested by Jane Doe

Mass of container,Mc (g) 20.0After 3

min.

After 1

more

min.

After 1

more

min.

After 1

more

min.

After 1

more

min.

Initial mass of container + wet specimen,Mcws (g) 155.0 155.0 155.0 155.0 155.0

Mass of container + dry specimen,Mcs(g) 131.8 122.3 121.5 121.3 121.2

Mass of water,Mw=Mcws Mcs (g) 23.2 32.7 33.5 33.7 33.8

Mass of solid particles,Ms= Mcs Mc(g) 111.8 102.3 101.5 101.3 101.2

Moisture contentw = MwMs

100%(%) 20.75 31.96 33.00 33.27 33.39

Percent difference in water content (%) 11.21 1.04 0.27 0.12

Figure 2.1: Example of water content by microwave oven calculation

2.3 Water Content by Oven Method

Drying takes at least 12 hours in a standard oven, but the temperature is constant avoiding problems with

overheating. If you have a large sample, overheating is likely in a microwave oven, therefore the standard

oven is recommended.

Texas A&M University G. Biscontin


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2.3.1 Standard Reference

ASTM D 2216- Standard test method for laboratory determination of water (moisture) content of soil and

rock by mass.


The following items will be required for this testing method:

A drying oven at a temperature of 110oC 5oC.

A scale with readability of 0.01 g is required for specimens with mass of less than 200 g.

Specimen container suitable for use in an oven. For small samples (less than 200 g) use the aluminumcontainers with a lid to prevent moisture loss before drying and moisture gain from the air after drying.

The containers must be dry.

Gloves or holders to handle the container.

Tools such as knives, or spatulas.

A marker, if the container does not have an identifying feature.

2.3.3 Procedure

1. Make sure you have a copy of the appropriate moisture content determination form ready for use.

2. Determine the mass of a clean, dry container or dish, and record it. Remember to record the container

ID or mark the container. Many similar containers are placed in the oven at the same time and may be

moved. You want to make sure you will be able to find your specimen.

3. Place the soil specimen in the container, and immediately determine and record the total mass.

4. Place contained and soil specimen in the oven for at least 12 hours. Longer drying times will not

compromise the results.

5. After the set time has elapsed, remove the container and soil from the oven taking care not to burn

yourself, and immediately record the mass.

6. Calculate the water content.

2.3.4 Calculations

Follow the same procedure as above in section2.2.5.



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2. Determining Water Content of Soil Specimens 7

Moisture Content Determination by Microwave Oven

Sample No. Project

Boring No. Location

Depth

Description of sample

Date Tested by

Mass of container,Mc (g)After 3

min.

After 1

more

min.

After 1

more

min.

After 1

more

min.

After 1

more

min.Initial mass of container + wet specimen,Mcws (g)

Mass of container + dry specimen,Mcs(g)

Mass of water,Mw=Mcws Mcs (g)

Mass of solid particles,Ms= Mcs Mc(g)


100%(%)

Percent difference in water content (%)

Moisture Content Determination by Oven

Sample No. Project

Boring No. Location

Depth


Date Tested by

Mass of container,Mc (g)

Initial mass of container + wet specimen,Mcws (g)

Mass of container + dry specimen,Mcs(g)

Mass of water,Mw=Mcws Mcs (g)

Mass of solid particles,Ms= Mcs Mc(g)


100%(%)



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Nominal diameter of Approximate Minimum

largest particles Mass of Portion

in. (mm) g

3/8 (9.5) 500

3/4 (19.0) 1000

1 (25.4) 20001.5 (38.1) 3000

2 (50.8) 4000

3 (76.2) 5000

3.3.3 Procedure

1. Clean each sieve to remove any soil left over from previous tests. Use the soft brush on the finer mesh

sieve and the wire brush on the coarser mesh sieve. Take care not to damage the mesh.

2. Measure and record the mass of each sieve, including the bottom pan.

3. Obtain the appropriate amount of sample.

4. Weigh and record the mass of the sample selected.

5. Assemble the sieves in order from largest to smallest so that the coarsest is at the top and the finest is

on the bottom followed by the pan.

6. Place the sample on to the top sieve taking care not to lose any of the mass and place the lid securely

on top.

7. Place the set of sieves in the sieve shaker and adjust the clamps to secure the sieves.

8. Set the shaker on high and set the timer to five minutes.

9. Remove the sieves from the sieve shaker

10. To insure that all the particles passed though the appropriate sieve, tap each sieve over a sheet of paper,

starting with the top sieve. Put any material that falls on to the paper into the next sieve and repeat the

process with the next sieve.

11. Measure and record the mass retained in each sieve.

12. Sum the mass of the material retained on each sieve to verify that there has been no change in the total

mass of the sample. (Note: A mass loss of less than 2% is acceptable.)

3.3.4 Calculations

Determine the weight of soil that is retained on each sieve,Wi.

Calculate the percent of soil that is retained on each sieve (%Ri):

%Ri=WiW 100 (3.1)



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3. Particle Size Analysis of Soils 11

Calculate the percent passing each sieve (%Pi):

%Pi= 100i

k=1

%Ri (3.2)

Plot the percent passing values on the grain size analysis chart provided.

3.4 Particle size analysis of fine grained fraction


Stirring apparatus.

Hydrometer, type 151H or 152H.

Sedimentation cylinder, glass cylinder marked for a volume of 1000 ml.

A solution of 40 g/l solution of sodium hexametaphosphate (or Calgon) in distilled water is used as adispersing agent and will be provided

Thermometer, accurate to 1oF (0.5oC).

Graduated beaker to 250 ml capacity.

Timer.

3.4.2 Hydrometer Calibration

The specific gravity of the solution of water and dispersing agent is higher than the specific gravity of distilled

water. This difference must be accounted for when using the equations for percentage of soil remaining in

suspension in section 3.4.4, which were developed for distilled water. In addition, the hydrometers were

calibrated at a constant temperature of 68oF (20oC), which cannot be ensured in our laboratory. Finally,

hydrometers are graduated by the manufacturer to be read at the bottom of the meniscus formed by the

liquid on the stem. However, given the difficulty of conducting a reading at the bottom of the meniscus

through the soil-water suspension, the readings should be taken at thetopof the meniscus and then corrected.

The combined amount of the corrections for these three items is called composite correction and should be

determined before or while conducting the actual test.

For convenience, measurement of the composite correction can be made at a few different temperatures

spanning the range expected during the test, and the result graphed. The correction for intermediate temper-

atures can be estimated using a linear approximation.

Calibration procedure

1. In a graduate cylinder, mix 125 ml of the 40 g/l solution of sodium hexametaphosphate (or Calgon)

and then distilled water up to 1000 ml.

2. Allow the temperature of the solution to become in equilibrium with the temperature in the room.

3. Place the hydrometer in the solution, allow to adjust to the temperature and stop moving.

4. Read the hydrometer at thetopof the meniscus formed on the stem.



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5. The composite correction for hydrometer 151H is the difference between this reading and one; for

hydrometer 152GH it is the difference between the reading and zero.

6. Repeat the measurement in parallel with your hydrometer measurements in the soil-water-dispersing

agent mix, when the room temperature changes.

3.4.3 Procedure

1. Obtain the equivalent of 50 g of air dried soil from the material passing the #200 sieve (do not oven

dry the soil).

2. Determine the hygroscopic water content (due to humidity in the air) using an additional 10-15 g of

soil.

3. Mix the soil to a thick slurry using 125 ml of the distilled water-dispersing agent solution.

4. Mix the slurry in a stirring apparatus for 60 seconds.

5. Transfer to the sedimentation cylinder and fill with distilled water up to the 1000 ml mark.

6. Mix thoroughly: cover the sedimentation cylinder mouth using a rubber glove and your hand and turn

the cylinder upside down and back for 1 minute.

7. Set the cylinder down and quickly start the timer. Take readings using the hydrometer at 4, 15, 30, 60,

90, 120 seconds. Be careful in inserting the hydrometer, so that it will be stabilized as soon as possible

and leave in the suspension for the first 2 minutes. Take readings at thetopof the meniscus.

8. Repeat the mixing process and take a second set of readings for the first 2 minutes.

9. Remove the hydrometer from the suspension and place with a spinning motion in a cylinder filled with

distilled water. To take the following readings, carefully place the hydrometer in the suspension about

20-25 s before the reading is due.

10. Take readings at 5, 15, 30, 60, and 1140 minutes. Place the hydrometer into the distilled water imme-

diately after each reading. After each reading, take the temperature of the suspension by inserting the

thermometer into the suspension.

11. At the end of the experiment, obtain the final dry weight of soil.

3.4.4 Calculations

Hygroscopic correction factor

Determine the hygroscopic correction factor based on the determination of the hygroscopic water content

results:

HygroscopicCF =WsWt

(3.3)

where:Ws is the weight of the soil after oven drying and Wtis the initial weight of the air dry sample.



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3.5 Forms

Sieve Analysis of Coarse Fraction

Sample No. Project

Boring No. Location

Depth


Date Tested by

Total weight of sample

Sieve No. Weight of

Sieve

Weight of

Sieve + Soil

Weight of Soil

Retained

Percentage

Retained

Percentage

Passed

(g) (g) (g) (%) (%)

Total weight of soil (g)



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HydrometerAnalysis

Date

Testedby

SampleNo.

Project

Boring

Depth

(A)Hygroscopicwater

content

(1)CupNo.

(2)Massofcup

(3)Masscup+soil(aird

ry)

(4)Masscup+soil(ovendry)

(5)Massofwater

(6)Massofsoil(ovendry)

(7)Massofsoil(airdry)

(8)Hygroscopicwate

rcontent

(9)Hygroscopiccorrectionfactor

(B)HydrometerAnalys

is

HydrometerType

SpecificGravityofSoil(Gs)

Massofairdrysoil

Calculatemassofovendrysoil

Date

Time

Elapsed

Time

ActualHy-

drometer

Reading

Composite

Correction

Hy

drometer

Re

ading

-

Co

rrection

Temperature

Effective

Hydro

me-

terDepth

Kfromtable

Diameterof

particle,D

Percent

finer

in

suspension

(min)

(rh)

(R

h)

(degreesC)

(mm)

(%)



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4. Atterberg Limits: Liquid Limit, Plastic Limit, and Plasticity Index of Soils 21

The liquid limit is defined as the water content at which a standard groove cut in the remolded soil sample

by a grooving tool closes over a length of 13 mm (0.5 in) at exactly 25 blows of the liquid limit cup falling

from a height of 10 mm on a hard rubber base. It is very difficult to mix the soil at the right water content,

even after a number of trials. However, if different trials are plotted on a semi-logarithmic scale they should

lie on a straight line and the liquid limit could be taken as the value of water content where the line crosses

the 25 blows mark. For this reason, in a liquid limit test we try to mix the soil at least three different watercontents aiming at blow counts above and below 25.

1. Mix the soil thoroughly with enough distilled water to reach a consistency requiring about 25 to 35

blows of the liquid limit device to close the groove. This is about the consistency of creamy peanut

butter. Keep in mind that it is easier to add water than to take it away, so try to aim for the thicker

consistency.

2. Using a spatula, place a portion of the prepared soil in the cup of the liquid limit device at the point

where the cup rests on the base, squeeze it down, and spread it into the cup to a depth of about 10 mm

at its deepest point, tapering to form an approximately horizontal surface. Take care to eliminate air

bubbles from the soil pat, but form the pat with as few strokes as possible. Keep the unused soil in the

mixing/storage dish. Cover the dish to retain the moisture in the soil.

3. Form a groove in the soil pat by drawing the tool, beveled edge forward, through the soil on a line

joining the highest point to the lowest point on the rim of the cup. When cutting the groove, hold the

grooving tool against the surface of the cup and draw in an arc, maintaining the tool perpendicular to

the surface of the cup throughout its movement.

4. Verify that no crumbs of soil are present on the base or the underside of the cup. Lift and drop the cup

by turning the crank at a rate of approximately 2 drops per second until the two halves of the soil pat

come in contact at the bottom of the groove along a distance of 13mm ( 12

in).

5. Record the number of drops, N, required to close the groove.

6. Quickly remove a slice of soil approximately the width of the spatula, along the groove and including

the portion of the groove in which the soil flowed together, place in a container of known mass, and

obtain a water content. Try to determine water content as soon as possible. The sample is small and

looses water quickly through evaporation.

7. Return the soil remaining in the cup to the mixing cup. Wash and dry the cup and grooving tool and

reattach the cup to the carriage in preparation for the next trial.

8. Remix the entire soil specimen in the dish adding distilled water to increase the water content of the

soil and decrease the number of blows required to close the groove.

9. Repeat steps 1-8 for at least two additional trials producing successively lower numbers of blows to

close the groove. One of the trials shall be for a closure requiring 25 to 35 blows, one for closure

between 20 and 30 blows, and one trial for a closure requiring 15 to 25 blows.

4.3.4 Calculation

Plot the relationship between the water content,wn, and the corresponding number of drops, N, on thegraph provided. Draw the best straight line through the three or more plotted points.

Take the water content corresponding to the intersection of the line with the 25-drop abscissa as theliquid limit of the soil and round to the nearest whole number. Computational methods may be substi-

tuted for the graphical method for fitting a straight line to the data and determining the liquid limit.



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4.4 Determination of Plastic Limit


Ground glass plate

Metal rod, 3.2 mm diameter

Balance

Water content cup

4.4.2 Procedure

1. Select about 20 g of soil from the material prepared for the liquid limit test.

2. Reduce the water content of the soil to a consistency at which it can be rolled without sticking to the

hands by spreading or mixing on the glass plate.

3. From this plastic limit specimen, select a 1.5 to 2.0 g portion. Form the selected portion into a ball.

4. Roll the mass between the palm or fingers and the glass plate to form a thread of uniform diameter

throughout its length. Keep rolling until the thread reaches 3.2 mm ( 18

in) diameter. Compare to the

metal rod to determine if the diameter is 3.2 mm. The process should take no more than 2 minutes for

each thread.

5. When the thread has reached a 3.2 mm diameter, break it into pieced and knead together in a ball.

Repeat the rolling and kneading process until the thread crumbles and the soil can no longer be rolled

into a 3.2 mm thread. Do not cheat, be consistent: apply the same rolling pressure during each stage of

the rolling and do not pretend to roll while you wait for the soil to dry and crumble. If the soil breaks

into threads of shorter length, roll each of these shorter pieces into threads 3.2 mm in diameter and

repeat the kneading and rolling process.

6. Collect the broken pieces in a water content cup and cover to prevent further drying while rolling the

next 1.5-2.0 g of soil.

7. Select another 1.5 to 2.0 g portion of soil from the plastic limit specimen and repeat the operations

steps 3-6 until the container has at least 6g of soil.

8. Use the 6 g of soil to obtain the water content according to the procedures in chapter2.

9. Go through the procedure in steps 1-8 until you have obtained two 6 g samples and water content

values. The water contents should not have a difference of more than 1.4%. The plastic limit is the

average of the two water content values.

4.5 Plasticity Index

Calculate the plasticity index as follows:

P I=LL P L (4.1)

where:



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4. Atterberg Limits: Liquid Limit, Plastic Limit, and Plasticity Index of Soils 23

LL = liquid limit

PL = plastic limit



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Atterberg Limits Determination

Sample No. Project

Boring No. Location

DepthDescription of sample

Date Tested by

Liquid Limit Determination

Can No.

Mass of can (g)

Mass of wet soil + can (g)

Mass of dry soil + can (g)

Mass of dry soil (g)

Mass of water (g)

Water content, (%)

No. of drops

LIQUID LIMIT =

PLASTIC LIMIT =PLASTICITY INDEX =

Plastic Limit Determination

Can No.

Mass of can (g)

Mass of wet soil + can (g)

Mass of dry soil + can (g)

Mass of dry soil (g)

Mass of water (g)

Water content, (%)



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Chapter 5

Liquid Limit of Soils using the Drop Cone

Penetrometer

by S.E. Tucker and Z. Medina-Cetina

5.1 Purpose

This apparatus is used commonly in Europe as a replacement for Casagrandes method of determining the

liquid limit of soils. It has been argued that this method is better because it is a static test relying only on

the shear strength of the soil. For certain soils, sometimes it is difficult to obtain repeatable results using the

Casagrande method in a reasonable amount of time. In this method the liquid limit is the water content at

which a cone penetrates the soil for a calibrated distance when it is allowed to free fall for 5 seconds.

5.2 Standard Reference

British Standard 1377: 1990 Part 2

5.3 Determination of Liquid Limit Using Drop Cone Penetrometer


Drop cone penetrometer apparatus

200 g of dry soil passing the No 200 sieve

Glass plate

Water content cup

Spatula and mixing tools

5.3.2 Procedure

1. Place the air dried soil in a plastic bag.


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5. Liquid Limit of Soils using the Drop Cone Penetrometer 27

Figure 5.2: Drop cone penetrometer release button.

Figure 5.3: Drop cone penetrometer dial gauge reading.



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14. The first reading should be approximately 15 mm, if it is higher than 17 the soil must be dried and the

test rerun.

15. Retract the cone from the cup and remove approximately 10-15 grams of soil using a spatula so that

the water content may be obtained.

16. Remove the rest of the soil from the cup and remix with the soil on the plate, add very little water tothis (1-2 ml) and mix the soil thoroughly.

17. Clean the cup and repeat steps 6-15 until a minimum of 4 points have been collected, moving from

drier to wetter conditions.

5.3.3 Calculation

Plot the penetration depth versus the water content for each test and fit the data with a best fit line

On the same graph, plot the following points and fit them with a best fit line. This is the calibrationline

Penetration (mm) Water Content(%)20.5 25

21 40

22 72

23 100

Where the calibration line and best fit line for your data intersect is the water content where the samplesliquid limit occurs



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Chapter 6

Classification of Soils According to the

Unified Soil Classification SyStem (USCS)

The Unified Soil Classification System (USCS) is based on the classification scheme developed by Arthur

Casagrande for the United States Army in the 1940s. In its simplest form, it consists in assigning a two- orfour-lettergroup symbolto the soil sample.

6.1 Definitions

fines: soil particles passing the #200 sieve (nominal diameter smaller than 0.075mm).

Coefficient of uniformity:Cu= D60D10

.

Coefficient of curvature:Cc= Cz = D2

30

D10

D60

.

Plasticity Index: PI = LL-PL.

6.2 Initial Classification

6.2.1 Highly Organic Soils

Organic soils are recognized by:

large presence of organic materials;

dark brown, dark gray or black color;

organic odor, especially when wet

very soft consistency

In this case, the material is classified as a peat, with symbol PT, and no further analysis is necessary.


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6.2.2 Non Highly Organic Soils

1. Determine gradation curve by sieve analysis. Use only the material with size smaller than 3in (75mm).

But report the percentage (by weight) of these large particles.

2. If the soil contains less than 5% fines a detailed sieve analysis is required to estimate the values of the

coefficient of uniformity,Cu, and the coefficient of curvature,Ccor Cz.

3. If the soil contains between 5% and 12% fines, the liquid limit and the plastic limit of the fines should

be determined, in addition to the detailed gradation curve andCu,Cc.

4. If the soil contains more than 12% fines the liquid limit and the plastic limit of the fines should be

determined, but it is sufficient to estimate the percentage of soil in the sand and gravel range. The

gradation characteristics,Cu and Cc, are not required.

6.3 Procedure for Classification of Fine Grained Soils

Follow this procedure if 50% or more by weight passes the #200 sieve. This is equivalent to saying that 50%or more by weight has a nominal diameter smaller than 0.075mm.

Figure 6.1: Plasticity chart (from ASTM Standard D2487).

1. Calculate the plasticity index (PI).

2. Compare with the plasticity chart:

LL>50 and PI>A line High plasticity clay (CH)

LL>50 and PI


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6. Classification According to USCS 31

If the soil has organic content: refer to ASTM standard D2487 on the proper procedure. In short,you need to oven dry the specimen to eliminate the organic material and calculate the LL on the

oven dried specimen. The classification is based on the difference between the LL before and

after oven drying.

3. You can add more information on the soil specimen classification after the main group symbol.

If 15% to 30% of the soil had nominal diameter larger than 0.075mm, use with sand or withgravel, depending on which is predominant.

If 30% to 50% of the soil had nominal diameter larger than 0.075mm, use sandy or withgravelly, depending on which is predominant.

6.4 Procedure for Classification of Coarse Grained Soils

Follow this procedure if 50% or more by weight is retained by the #200 sieve. This is equivalent to saying

that 50% or more by weight has a nominal diameter larger than 0.075mm.

1. >50% of the specimen is retained on the #4 sieve (nominal diameter larger than 4.75mm) Gravel(G)

If12% fines and fines are silt based on plasticity chart Silty gravel (GM)

If>12% fines and fines are CL-ML based on plasticity chart Silty clayey gravel (GM-GC)

2. >50% of the specimen is retained between the #4 and the #200 sieves (nominal diameter between0.075 and 4.75mm) Sand (S)

If


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Chapter 7

Visual Classification of Soils

7.1 Purpose

During drilling and sampling operations in the field classification has to be carried out quickly and without

gradation analyses or Atterberg limits. An approximate procedure is then used and the description is notedon the boring log. The initial boring log is often checked later in the laboratory with the help of the retrieved

soil samples. Even in the laboratory a small portion of the samples will be actually tested for classification

purposes. The specimens for classification testing are chosen from the different layers that were identified

during field operations and from previous information, where available. The remaining samples are classified

based on their similarities in the tested samples and visual-manual procedures illustrated below.


ASTM D2488- Standard practice for description and identification of soils (visual-manual procedure).

7.3 Terminology

Gravel Particles of rock that will pass a 3 in (75 mm) sieve and be retained on a No. 4 (4.75 mm) sieve with

the following subdivisions:

coarse - passes 3 in (75 mm) sieve and retained on 34

in (19 mm) sieve.

fine - passes a 3.4 in (19 mm) sieve and retained on a No.4 (4.75 mm) sieve.

Sand Particles of rock that will pass a No. 4 (4.75 mm) sieve and be retained on a No. 200 (75 m) sievewith the following subdivisions:

coarse - passes a No. 4 (4.75 mm) and retained on No. 10 (2.00 mm) sieve

medium - Passes a No. 10 (2.00 mm) sieve and is retained on a No. 40 (425m) sieve.

Silt Soil passing a No. 200 (75m) sieve that is non-plastic or very slightly plastic and that exhibits little ofno strength when dry. For classifications, a silt is fine grained soil or the fine grained portion of a soil,

with a plasticity index less than 4, or the plot of plasticity index versus liquid limit falls below the A

line.


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Clay Soil passing a No. 200 (75m) sieve that can be made to exhibit plasticity within a range of watercontents, and that exhibits considerable strength when air-dry. For classifications a clay is a fine

grained soil or a fine grained portion of a soil, with a plasticity index equal to or greater than 4, and

the plot of plasticity index versus liquid limit falls on or above the A line.

Organic Silt A silt with sufficient organic content to influence the soil properties. For classifications, an

organic silt is a soil that would be classified as a silt, except that its liquid limit value after oven drying

is less than 75% of its liquid limit value before oven drying.

Organic Clay A clay with sufficient organic content to influence the soil properties. For classification, an

organic clay is a soil that would be classified as a clay, except that its liquid limit value after oven

drying is less than 75% of its liquid limit value before oven drying.

7.4 Descriptive Information for Soils

Angularity Describe the angularity of the sand (coarse sizes only), gravel, cobbles, and boulders, as angular,

subangular, subrounded, or rounded in accordance with the criteria in table7.1.A range of angularity

may be stated, such as subrounded to rounded.

Shape Describe the shape of gravel, cobbles, and boulders as flat, elongated, or flat and elongated if they

meet the criteria if they meet in table 7.2. Otherwise do not mention the shape. Indicate the fraction

of particles that have that shape; for example: one-third of the gravel is flat.

Color Described the color of the sample when moist.

Odor Describe the odor of the sample if organic or unusual

Moisture Condition Describe the moisture condition as dry, moist, or wet in accordance with the criteria

in table7.3

Consistency For intact fine-grained soil, describe the consistency as very soft, soft, firm, hard, or very hardin accordance with the criteria in table7.4.This observation is inappropriate for soils with significant

amounts of gravel.

Cementation Describe the cementation of intact coarse grained soil as weak, moderate, or strong, in accor-

dance with Table7.5.

Range of particle sizes For gravel and sand components, described the range of particle sizes within each

components. For example, about 20% fine to coarse gravel, about 40% fine to coarse sand.

Maximum particle size Describe the maximum particle size found in the sample for each size classifica-

tion. For example, the largest particle size for sand size particles and the largest particle for gravel size

particles.

Description Criteria

Angular Particles have sharp edges and relatively plane sides with unpolished surfaces

Subangular Particles are similar to angular description but have corners and edges

Subrounded Particles have nearly plane sides but have rounded corners and edges

Rounded Particles have smoothly curved sides and no edges

Table 7.1: Criteria for describing angularity of coarse-grained particles.



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7. Visual Classification of Soils 35

The particle shape shall be described as follows where length, width, and thickness refer to

the greatness, intermediate, and least dimensions of a particle respectively.Description Criteria

Flat Particles with width/thickness>3

Elongated Particles with length/width>3

Flat and Elongated Particles meet criteria for both flat and elongated

Table 7.2: Criteria for describing particle shape.


Dry Absence of moisture, dusty, dry to the touch

Moist Damp but no visible water

Wet Visible free water, usually soil is below water table

Table 7.3: Criteria for describing moisture conditions.


Very soft Thumb will penetrate soil more that 1in. (25mm)

Soft Thumb will penetrate soil about 1in. (25mm)

Firm Thumb will indent soil about 1/4in. (6mm)

Hard Thumb will not indent soil but will readily intent with thumbnail

Very Hard Thumbnail will not indent soil

Table 7.4: Criteria for describing consistency


Weak Crumbles or breaks with handling of little finger pressure

Moderate Crumbles or breaks with considerable finger pressure

Strong Will not crumble with finger pressure

Table 7.5: Criteria for Describing Cementation

Hardness Describe the hardness of coarse sand and larger particles.

7.5 Procedure for Identifying Fine-Grained Soils

Select a representative sample of the material for examination. Remove particles larger than the No. 40 sieve

until a specimen equivalent to about a handful of material is available. Use this specimen for performing the

dry strength, dilatancy, and toughness test.

Dry Strength Select a few dry lumps of about 1/2in. in diameter. Test the strength of the dry pieces by

crushing between the fingers. Note the strength as none, low, medium, high, or very high in accordance

with the criteria in Table7.6. If natural dry lumps are used do not use the results of any of the lumps

that are found to contain particles of coarse sand.

Dilatancy From the specimen select enough material to mold into a ball about 1/2in. in diameter. Mole the

material, adding water if necessary, until it has a soft, but not sticky consistency. Smooth the soil in

the palm of one hand with a small spatula. Shake horizontally, striking the side of the hand vigorously

against the other hand several times. Note the reaction of water appearing on the surface of the soil.



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None The dry specimen crumbles into powder under mere pressure of handling

Low The dry specimen crumbles into powder with some finger pressure

Medium The dry specimen breaks into pieces or crumbles with considerable finger pressure

High The dry specimen cannot be broken with finger pressure

Very High The dry specimen cannot be broken with thumb and a hard surface

Table 7.6: Criteria for Describing Dry Strength

Squeeze the sample by closing the hand or pinching the soil between the fingers, and note the reaction

as none, slow, or rapid in accordance with the criteria in Table 7.7. The reaction is the speed at which

the water appears while shaking, and disappears while squeezing.


None No visible change in specimen

Slow Water appears slowly on the surface during shaking and does not disappear or

disappears slowly upon squeezingRapid Water appears quickly during shaking and disappears quickly during squeezing

Table 7.7: Criteria for Describing Dilatancy

Toughness Following the completion of the dilatancy test, the test specimen is shaped into an elongated pat

and rolled by hand on a smooth surface or between the palms into a thread about 1/8in. in diameter.

Fold the threads and reroll repeatedly until the thread crumbles at a diameter of about 1/8in. The thread

will crumble at a diameter of 1/8 in. when the soil is near the plastic limit. Note the pressure required

to roll the thread near the plastic limit. Also, note the strength of the thread. After the thread crumbles,

the pieces should be lumped together and kneaded until the lump crumbles. Note the toughness of the

material during kneading.Describe the toughness of the thread and lump as low, medium or high inaccordance with the criteria in table7.8.


Low Only slight pressure is required to roll the thread near the plastic limit. The

thread and lump are soft and weak

Medium Medium pressure is required to roll the thread to near the plastic limit. The

thread and lump have medium stiffness.

High Considerable pressure is needed to roll thread near the plastic limit. The thread

and lump have very high stiffness

Table 7.8: Criteria for Describing Toughness

Plasticity On the basis of observations made during the toughness test, describe the plasticity of the material

in accordance with the criteria given in Table 7.9.

7.6 Identification of Inorganic Fine-Grained Soils

Identify the soil as follows:



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Nonplastic A 1/8in. thread cannot be rolled at any water content

Low The thread can barely be rolled and the lump cannot be formed when drier than

the plastic limit

Medium The thread is easy to roll and not much time is required to reach the plastic

limit. The thread cannot be rolled after reaching the plastic limit. The lumpcrumbles drier than the plastic limit

High It takes considerable time rolling and kneading to reach the plastic limit. The

thread can be rolled several times after reaching the plastic limit. The lump

can be formed without crumbling when drier than the plastic limit.

Table 7.9: Criteria for Describing Plasticity

Soil Symbol Dry Strength Dilatancy Toughness

ML None to Low Slow to rapid Low or thread cannot be formed

CL Medium to High None to Slow Medium

MH Low to Medium None to Slow Medium

CH High toVery High None High

Table 7.10: Identification of Inorganic Fine-Grained Soils from Manual Test

7.7 Procedure for identifying Coarse-Grained Soils

1. The soil is a gravel if the percentage of gravel is estimated to be more than the percentage of sand.

2. The soil is a sand if the percentage of gravel is estimated to be equal to or less than the percentage of

sand.

3. The soil is a clean gravel or clean sand if the percentage of fines is estimated to be 5% of less.

4. Identify the soil as well-graded gravel, GW, or as well-graded sand, SW, if it has a wide range of

particle sizes and substantial amounts of the intermediate particle sizes.

5. Identify the soil as a poorly graded gravel, GP, or as a poorly graded sand, SP, if it consists predom-

inantly of one size (uniformly graded), or it has a wide range of sizes with some intermediate sizes

obviously missing.

6. The soil is either a gravel with fines or a sand with fines if the percentage of fines is estimated to be

15% or more.

7. Identify the soil as a clayey gravel, GC, or a clayey sand, SC, if the fines have the properties of clays.

8. Identify soil as a silty gravel, GM, or a silty sand, SM, if the fines have the properties of a silt.

9. If the soil is estimated to contain 10% fines, give the soil a dual identification using two group symbols.

The first group symbol shall correspond to a clean gravel or sand (GW,GP, SW, SP) and the second

symbol shall correspond to a gravel or sand with fines (GC, GM, SC, SM).

10. The group name shall correspond to the first group symbol plus the words with clay or with silt

to indicate the plasticity characteristics of the fines. For example: well-graded gravel with clay,

GW-GC or poorly graded sand with silt, SP-SM.



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Classification Data SheetSample Classification Comments



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Chapter 8

Compaction Using Standard Effort

8.1 Purpose

Soil placed as engineering fill (embankments, foundation pads, road bases) must be compacted to the se-

lected density and water content to ensure the desired performance and engineering properties such as shearstrength, compressibility, or permeability. Also, foundation soils are often compacted to improve their en-

gineering properties. Laboratory compaction tests provide the basis for determining the percent compaction

and water content needed in the field, and for controlling construction to assure that the target values are

achieved.

In a geotechnical laboratory you would prepare at least four (preferably five) specimens with water

contents bracketing the estimated optimum water content. A specimen having a water content close to

optimum would be prepared first by trial additions of water and mixing and then water contents for the rest

of the specimens would be selected to provide at least two specimens wet and two specimens dry of optimum,

and water contents varying by about 2%, but no more than 4%. In this laboratory exercise each group in your

section will compact one of the specimens at a specific water content, as directed by the laboratory instructor,

and the results from all the groups will be combined later.

The data, when plotted, represents a curvilinear relationship known as the compaction curve. The values

of optimum water content and standard maximum dry unit weight are determined from the compaction curve.

These test methods apply only to soils (materials) that have 20% or less by mass of particles retained on

the No.4 (4.75 mm) sieve.


ASTM D 698- Standard test methods for laboratory compaction characteristics of soil using standard effort

(12,400 ft-lbf/ft3 (600 kN-m/m3)).

8.3 Required Materials and Equipment

Mold - A cylindrical metal mold having a 4.000 0.016 in (101.6 0.4 mm) average inside diameter,a height of 4.584 0.018 in (116.4 0.5 mm) and a volume of 0.0333 0.0005f t3 (944 14 cm3).

Rammer - with free fall of 12 0.05 in (304.8 1.3 mm) from the surface of the specimen. The massof the rammer is 5.5 0.02 lbm (2.5 0.01 kg).

Sample extruder - A jack for extruding compacted specimens from the mold.


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Balance - with 1 g readability.

straight edge - for leveling off compacted sample

mixing tools - for mixing the sample of soil with increments of water.

8.4 Procedure

8.4.1 Specimen preparation

1. Obtain from your laboratory instructor a sample of the soil to be tested. You will need approximately

2 kg.

2. Without previously drying the sample, pass it through a No. 4 (4.7 mm) sieve. Determine the water

content of the processed soil. See chapter2for the procedure.

3. Double check the target water content for your specimen with the laboratory instructor.

4. Calculate how much water should be added or subtracted from your sample to obtain the desired water

content. Remember to account for the moisture already present in the sample and use the exact value

for the mass of the soil, not the approximate number.

5. To add water, spray it into the soil during mixing; to remove water, allow the soil to dry in air at ambient

temperature Mix the soil frequently during drying to maintain an even water content distribution.

Thoroughly mix each specimen to ensure even distribution of water throughout and then place in a

separate covered container.

8.4.2 Compaction

1. Determine and record the mass of the mold or mold and base plate.

2. Assemble and secure the mold and collar to the base plate. Place on the concrete floor of the laboratory,

NOTon the counters.

3. The specimen is compacted in 3 layers. Remember that after compaction the layers should be approx-

imately equal in thickness and the last layer should extend above the top of the mold, but no more than1

4in (6 mm). Place approximately 1/3 of the loose soil into the mold for each layer and spread into a

layer of uniform thickness.

4. Compact each layer with 25 blows. In operating the manual rammer, do not lift the guide sleeve

during the rammer upstroke. Hold the guide sleeve steady and within 5o of vertical. Apply the blows

at a uniform rate of approximately 25 blows per minute and in such a manner as to provide complete,uniform coverage of the specimen surface. Usually this is achieved by moving the rammer along the

perimeter of the mold and using 5 blows to cover the whole area. Then the pattern is repeated for 5

times.

5. After compaction of the first two layers, trim any soil remaining on the mold walls or extending above

the compacted surface and include it with the soil for the next layer. Before placing the next layer of

soil scarify the surface of the compacted soil with a knife or other suitable tool to avoid separation of

the layers at the joints later in the test.



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8. Compaction Using Standard Effort 43

6. If the third layer extends above the top of the mold by more than 14

in (6 mm) or below the top of the

compaction mold, the specimen should be discarded.

7. Following compaction of the last layer, remove the collar and base plate from the mold. A knife may

be used to trim the soil adjacent to the collar to loosen the soil from the collar before removal to avoid

disrupting the soil below the top of the mold.

8. Carefully trim the compacted specimen even with the top of the mold by means of the straightedge

scraped across the top of the mold to form a plane surface even with the top of the mold. Initial

trimming of the specimen above the top of the mold with a knife may prevent the soil from tearing

below the top of the mold. Fill any holes in the top surface with unused or trimmed soil from the

specimen, press in with the fingers, and again scrape the straightedge across the top of the mold.

9. Determine and record the mass of the specimen and mold to the nearest gram.

10. Remove the material from the mold using the sample extruder.

11. Obtain a specimen for water content by using the whole specimen or a representative sample. Select a

suitable container and record its weight.

12. Weigh the container and the specimen.

13. Place in the oven for 24 hours. If the entire specimen is used, break it up to facilitate drying.

14. Record the weight of the oven dried specimen in the container.

8.5 Calculations

Post the following information as directed by the laboratory instructor: laboratory section (week day),group (color), date, mass of moist specimen in the mold, mass of mold, water content determination:

mass of moist soil after compaction and can, mass of can, mass of oven dried specimen an can. Seesection8.5for a form to fill.

Calculate the total unit weight of each specimen:

t=Mtg

Vm=

(Msm Mm)g

Vm(8.1)

where:

Mt= mass of moist soil

Msm= mass of the moist specimen and mold

Mm= mass of the moldVm= volume of the mold (944 cm

3)

g= acceleration of gravity (9.807 m/s2)

Calculate water content of each compacted specimen:

w=Mwg

Msg =

(Mwsc Msc)

(Msc M c (8.2)

where:



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Mw = mass of water

Ms= mass of dry soil

Mwsc = mass of wet soil and can

Msc= mass of dry soils and can

Mc= mass of can

w= water content

Calculate dry unit weight:

d= t1 + w

(8.3)

Plot the values and draw the compaction curve as a smooth curve through the points (see example,Fig. 3). Plot dry unit weight to the nearest0.1 lbf

ft3, (0.2 kN

m3)and water content to the nearest 0.1 %.

From the compaction curve, determine the optimum water content and maximum dry unit weight.

Plot the 100% saturation curve.



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Chapter 9

Measuring Suction with the Filter Paper

Method

9.1 Purpose

The filter paper method has long been used in soil science and engineering practice and it has recently been

accepted as an adaptable test method for soil suction measurements because of its advantages over other

suction measurement devices. Basically, the filter paper comes to equilibrium with the soil either through

vapor (total suction measurement) or liquid (matric suction measurement) flow. At equilibrium, the suction

value of the filter paper and the soil will be equal. After equilibrium is established between the filter paper

and the soil, the water content of the filter paper disc is measured. Then, by using filter paper water content

versus suction calibration curve, the corresponding suction value is found from the curve. This is the basic

approach suggested by ASTM Standard Test Method for Measurement of Soil Potential (Suction) Using

Filter Paper (ASTM D 5298). ASTM D 5298 employs a single calibration curve that has been used to infer

both total and matric suction measurements. The ASTM D 5298 calibration curve is a combination of both

wetting and drying curves. Bulut (2001) demonstrates that the wetting and drying suction calibrationcurves do not match, an observation that was also made by Houston et al. (1994). In this test, the wetting

curve as shown in Figure9.2is used because the filter paper becomes wet during the test.

9.2 Soil Suction Concept

In general, porous materials have a fundamental ability to attract and retain water. The existence of this

fundamental property in soils is described in engineering terms as suction, negative stress in the pore water.

In engineering practice, soil suction is composed of two components: matric and osmotic suction (Fredlund

and Rahardjo 1993). The sum of matric and osmotic suction is called total suction. Matric suction comes

from the capillarity, texture, and surface adsorptive forces of the soil. Osmotic suction arises from the

dissolved salts contained in the soil water. This relationship can be formed in an equation as follows:

ht = hm+ h (9.1)

where:

ht= total suction (kPa)

hm= matric suction (kPa)


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hp= osmotic suction (kPa)

Total suction can be calculated using Kelvins equation, which is derived from the ideal gas law using

the principles of thermodynamics and is given as:

ht=

RT

V ln P

Po

(9.2)

where:

ht= total suction

R= universal gas constant

T= absolute temperature

V= molecular volume of water

P/Po = relative humidity

P= partial pressure of pore water vapor

Po = saturation pressure of water vapor over a flat surface of pure water at the same temperature.

If equation9.2is evaluated at a reference temperature of 25o, the following total suction and relative

humidity relationship can be obtained:

ht = 137, 182 ln(P/Po) (9.3)

It can be said, in general, that in a closed system under isothermal conditions the relative humidity may

be associated with the water content of the system such as 100% relative humidity refers to a fully saturated

condition. Therefore, the suction value of a soil sample can be inferred from the relative humidity and

suction relationship if the relative humidity is known. In a closed system, if the water is pure enough, thepartial pressure of the water vapor at equilibrium is equal to the saturated vapor pressure at temperature, T.

However, the partial pressure of the water vapor over a partly saturated soil will be less than the saturation

vapor pressure of pure water due to the soil matrix structure and the free ions and salts contained in the soil

water (Fredlund and Rahardjo 1993).

In engineering practice, soil suction has usually been calculated in pF units (Schofield, 1935) (i.e., suc-

tion in pF = log10|suction in cm of water|). However, soil suction is also currently being represented inlog(kP a) unit system (Fredlund and Rahardjo 1993) (i.e., suction in log(kP a) = log10|suction in kPa|).The relationship between these two systems of units is approximately suction in log(kP a) = suction in pF- 1. Matric suction can be calculated from pressure plate and pressure membrane devices as the difference

between the applied air pressure and water pressure across a porous plate. Matric suction can be formed in a

relationship as follows:

hm= (ua uw) (9.4)

where:

hm= matric suction

ua= applied air pressure

uw = free water pressure at atmospheric condition



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9. Measuring Suction with the Filter Paper Method 49

The osmotic suction of electrolyte solutions, that are usually employed in the calibration of filter papers

and psychrometers, can be calculated using the relationship between osmotic coefficients and osmotic suc-

tion. Osmotic coefficients are readily available in the literature for many different salt solutions. Table 1

gives the osmotic coefficients for several salt solutions. Osmotic coefficients can also be obtained from the

following relationship (Lang 1967):

= wvmw

ln

P

Po

(9.5)

where:

f= osmotic coefficient

v= number of ions from one molecule of salt (i.e., v= 2 for NaCl, KCl, NH4Cland v= 3 forNa2SO4,CaCl2,Na2S2O3,etc.)

m= molality

w= molecular mass of water

w = density of water

The relative humidity term (P/Po) in eq. 9.5 is also known as the activity of water (aw) in physicalchemistry of electrolyte solutions. The combination of eq. 9.2and eq. 9.5gives a useful relationship that

can be adopted to calculate osmotic suctions for different salt solutions:

h = vRTm (9.6)

9.3 Required Materials and Equipment

Schleicher & Schuell No. 589-WH filter paper

Sensitive balance with accuracy of 0.0001 g

Constant temperature container (or cooler)

moisture tins and glass jars

PVC rings, electrical tape

tweezers and gloves

Oven and aluminum block

9.4 Procedure

A testing procedure for total suction measurements using filter papers can be outlined as follows:

1. At least 75% by volume of a glass jar should be filled with the soil; the smaller the empty space

remaining in the glass jar, the smaller the time period that the filter paper and the soil system require

to come to equilibrium.



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2. A ring type support, which has a diameter smaller than filter paper diameter and about 1 to 2cm in

height, is put on top of the soil to provide a non-contact system between the filter paper and the soil.

Care must be taken when selecting the support material; materials that can corrode should be avoided,

plastic or glass type materials are much better for this job.

3. Two filter papers one on top of the other are inserted on the ring using tweezers. The filter papersshould not touch the soil, the inside wall of the jar, and underneath the lid in any way.

4. Then, the glass jar lid is sealed very tightly with plastic tape.

5. Steps 1, 2, 3, and 4 are repeated for every soil sample.

6. After that, the glass jars are put into the ice-chests in a controlled temperature room for equilibrium.

Researchers suggest a minimum equilibrating period of one week (ASTM D 5298; Houston et al., 1994;

Lee 1991). After the equilibration time, the procedure for the filter paper water content measurements can

be as follows:

1. Before removing the glass jar containers from the temperature room, all aluminum cans that are used

for moisture content measurements are weighed to the nearest 0.0001 g. accuracy and recorded.

2. After that, all measurements are carried out by two persons. For example, while one person is opening

the sealed glass jar, the other is putting the filter paper into the aluminum can very quickly (i.e., in a

few seconds) using tweezers.

3. Then, the weights of each can with wet filter paper inside are taken very quickly.

4. Steps 2 and 3 are followed for every glass jar. Then, all cans are put into the oven with the lids half-

open to allow evaporation. All filter papers are kept at 105 5oCtemperature inside the oven for atleast 10 hours.

5. Before taking measurements on the dried filter papers, the cans are closed with their lids and allowed

to equilibrate for about 5 minutes. Then, a can is removed from the oven and put on an aluminum

block (i.e., heat sinker) for about 20 seconds to cool down; the aluminum block functions as a heat

sink and expedites the cooling of the can. After that, the can with the dry filter paper inside is weighed

very quickly. The dry filter paper is taken from the can and the cooled can is weighed again in a few

seconds.

6. Step 5 is repeated for every can.

9.5 Soil Matric Suction Measurements

Soil matric suction measurements are similar to the total suction measurements except instead of inserting

filter papers in a non-contact manner with the soil for total suction testing, a good intimate contact should

be provided between the filter paper and the soil for matric suction measurements. Both matric and total

suction measurements can be performed on the same soil sample in a glass jar as shown in Fig. 1. A testing

procedure for matric suction measurements using filter papers can be outlined as follows:



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9. Measuring Suction with the Filter Paper Method 51

Figure 9.1: Assembly for total and matric suction measurements.

9.6 Procedure

1. A filter paper is sandwiched between two larger size protective filter papers. The filter papers used in

suction measurements are 5.5cm in diameter, so either a filter paper is cut to a smaller diameter and

sandwiched between two 5.5cm papers or bigger diameter (bigger than 5.5cm) filter papers are used

as protection.

2. Then, these sandwiched filter papers are inserted into the soil sample in a very good contact manner

(i.e., as in Fig. 1). An intimate contact between the filter paper and the soil is very important.

3. After that, the soil sample with embedded filter papers is put into the glass jar container. The glass

container is sealed up very tightly with plastic tape.

4. Steps 1, 2, and 3 are repeated for every soil sample.

5. The prepared containers are put into ice-chests in a controlled temperature room for equilibrium.

9.7 Calculations

After obtaining all of the filter paper water contents, figure 9.2 is employed to get total suction and matric

values of the soil samples.



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Figure 9.2: Filter paper wetting calibration curve.

Paper Suction Determination

Sample No. Project

Boring No. Location

Depth


Date Tested by

Total Suction

Paper

Matric Suction

Paper

Container NumberMass of container (g)

Mass of wet paper + container (g)

Mass of wet filter paper (g)

Mass of hot container (g)

Mass of dry filter paper (g)

Mass of water in filter paper (g)

Water content of filter paper (%)



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Chapter 10

Hydraulic Conductivity

10.1 Purpose

Hydraulic conductivity is the parameter that tells us how fast water can flow through soil. This quantity is

measured to determine if a particular soil is a suitable material for a levee, dam or landfill liner, or filter.During this laboratory both the constant head and the falling head methods will be used.


ASTM D 2434- Standard test method for permeability of granular soils (constant head).

10.3 Fundamental Test Conditions

The following test conditions are prerequisites for laminar flow of water through granular soils, under

constant-head conditions:

Continuity of flow with no soil volume change during a test.

Flow with the soil voids saturated with water and no air bubbles in the soil voids.

Flow is steady state with no change in hydraulic

geotechnical laboratory manual

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