THE EFFECT OF DEGREE OF SATURATION ON THE RESULTS OF ...

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THE EFFECT OF DEGREE OF SATURATION ON THE RESULTS OF DIRECT SHEAR TESTS OF C-Φ SOIL M.Sc. THESIS HABTAMU KEFYALEW MOLLA HAWASSA UNIVERSITY, HAWASSA, ETHIOPIA SEPTEMBER, 2017

Transcript of THE EFFECT OF DEGREE OF SATURATION ON THE RESULTS OF ...

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THE EFFECT OF DEGREE OF SATURATION ON THE RESULTS OF DIRECT

SHEAR TESTS OF C-Φ SOIL

M.Sc. THESIS

HABTAMU KEFYALEW MOLLA

HAWASSA UNIVERSITY, HAWASSA, ETHIOPIA

SEPTEMBER, 2017

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THE EFFECT OF DEGREE OF SATURATION ON THE RESULTS OF DIRECT

SHEAR TESTS OF C-Φ SOIL

HABTAMU KEFYALEW MOLLA

A THESIS SUBMITTED TO THE

SCHOOL OF CIVIL ENGINEERING,

HAWASSA INSTITUTE OF TECHNOLOGY, SCHOOL OF

GRADUATE STUDIES

HAWASSA UNIVERSITY

HAWASSA, ETHIOPIA

IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE

DEGREE OF

MASTER OF SCIENCE IN CIVIL ENGINEERING

(SPECIALIZATION: GEOTECHNICAL ENGINEERING)

SEPTEMBER, 2017

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A MASTER OF THESIS APPROVAL

This thesis entitled with “The Effect of Degree of Saturation on the Results of Direct Shear

Tests of C-Φ Soil” has been approved by the advisors, examiners and school in partial

fulfillment of the requirement for the degree of Master of Science in Civil Engineering

Department Geotechnical Engineering stream.

Date of Defense: …………………………

APPROVED BY:

1. ________________ ___________________ ___________________

Chairperson Signature Date

2. _________________ __________________ ___________________

External Examiner Signature Date

3. _________________ __________________ ___________________

Internal Examiner Signature Date

4. _________________ ___________________ __________________

Name of major advisor Signature Date

5. _________________ ___________________ ___________________

SGC Signature Date

6. _________________ ___________________ ___________________

SGS Signature Date

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Acknowledgements

I would like to express my gratitude to my supervisor Dr. Yoseph Birru for initiating an

interesting study during his lecturing class, his personal commitment, interesting

discussion and valuable advice. His encourage and guidance leads me to follow his foot

step and to do this interested research. He has been continuously inspiring me throughout

the work and contributing with valuable assistance and supervision.

I express my sincere appreciation to the Ethiopian Road Authority for providing financial

support in the course of this research.

I would like to thank Ethiopian Construction Design & Supervision Works Corporation for

their Geotechnical Laboratory Facility permission to do my Laboratory works. Also

Grateful thanks go to all Ethiopian Construction Design & Supervision Works

Corporation, Geotechnical Laboratory staffs for their technical support in the laboratory.

I also thank my friends and colleagues for sharing knowledge and helping throughout this

research.

Finally, I would like to thank the love and support of my parents and the Almighty, whose

blessings gave me the strength to finish my research.

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Symbols and Abbreviations

c - Cohesion;

c' - Effective cohesion;

ew - Void ratio occopied by water;

e - Void ratio;

GS - Specific gravity of soil;

LL - Liquid limit;

n - Porosity;

OWC - Optimum Water Content;

PL - Plastic limit;

PI - Plasticity index;

S - Degree of saturation;

u - Pore water pressure;

USCS - Unified Soil Classification System;

V - Volume of total mass of the sample;

Vm - Volume of mold;

VS - Volume of soil;

VV - Volume of void;

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VW - Volume of water;

W - Water content;

Wd - Weight of dry soil;

WS - Weight of soil;

WW - Weight of water;

ϕ - Friction angle;

ϕ‟ - Effective Friction angle;

, t - Unit weight or total unit weight;

d - Dry unit weight;

d-max - Maximum dry unit weight;

s - Unit weight of soil;

w - Unit weight of water;

σ - Total stress;

σnf‟ - Effective normal stress at failure; and

τf - Shear stress on the failure plane at failure.

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Table of Contents

Acknowledgements ................................................................................................................. i

Symbols and Abbreviations ................................................................................................... ii

List of Table ......................................................................................................................... vii

List of Figure ...................................................................................................................... viii

List of Table (Appendix) ....................................................................................................... x

List of Figure (Appendix) ..................................................................................................... xi

Abstract ........................................................................................................................... xii

1. Introduction .......................................................................................................... 1

1.1 Background of Problems and Significance of the Study ..................................... 1

1.2 Research Objectives ............................................................................................. 2

1.3 Research Methodology ........................................................................................ 3

1.4 Scope and Limitations of the Study ..................................................................... 3

2. Literature Review ................................................................................................ 5

2.1 General ................................................................................................................. 5

2.2 Effect of Degree of Saturation Variation on Direct Shear Test Result ................ 6

2.3 Shear Strength for Soils ....................................................................................... 8

2.3.1 Friction Angle .................................................................................................. 9

2.3.2 Cohesion ........................................................................................................ 10

2.4 Compaction Curve ............................................................................................. 11

2.5 Soil Classifications ............................................................................................ 12

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2.6 Direct Shear Testing .......................................................................................... 13

2.6.1 A History of the Direct Shear Box Test ......................................................... 13

2.6.2 Significance and Use of Direct shear Test ..................................................... 14

3. Research Methodology ...................................................................................... 16

3.1 General ............................................................................................................... 16

3.2 Geotechnical Index Properties ........................................................................... 17

3.2.1 Water Content ................................................................................................ 17

3.2.2 Specific Gravity ............................................................................................. 18

3.2.3 Grain Size Distribution .................................................................................. 20

3.2.4 Free Swell ...................................................................................................... 21

3.2.5 Atterberge‟s (Consistency) Limits ................................................................. 22

3.3 Compaction Curve ............................................................................................. 23

3.4 Direct Shear Test ............................................................................................... 26

3.5 Experimental Work ............................................................................................ 28

3.5.1 Construction of Test and Preparation of Sample ........................................... 28

3.5.2 Degree of Saturation Controlled Soil Samples Preparation........................... 28

3.6 Correlation of Cohesion (C) and Friction Angle (Φ) With Degree of

Saturation… ..................................................................................................................... 29

4. Results and Discussions ..................................................................................... 30

4.1 General ............................................................................................................... 30

4.2 Geotechnical Index Properties ........................................................................... 30

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4.2.1 Water Content ................................................................................................ 30

4.2.2 Specific Gravity ............................................................................................. 30

4.2.3 Grained size distributions .............................................................................. 30

4.2.4 Free Swell ...................................................................................................... 32

4.2.5 Atterberge‟s (Consistency) Limits ................................................................. 32

4.3 Compaction Curve ............................................................................................. 33

4.4 Direct Shear Test ............................................................................................... 34

4.4.1 Shear Strength Parameters on Different Degree of Saturation. ..................... 34

4.4.2 Relationships between Cohesion (c), Angle of Internal Friction (ϕ) and

Degree of Saturation (S) ............................................................................................... 45

4.4.3 Analysis of the Effects of Degree of Saturation on the Cohesion (c) ............ 50

4.4.4 Analysis of the Effects of Moisture Content on the Angle of Internal Friction

(ϕ) ....................................................................................................................... 50

5. Summary, Conclusions and Recommendation .................................................. 52

5.1 Summary ............................................................................................................ 52

5.2 Conclusion ......................................................................................................... 52

5.3 Recommendation ............................................................................................... 53

References ........................................................................................................................... 55

Appendices........................................................................................................................... 58

Appendix A: List of Table ............................................................................................... 58

Appendix B: List of Figure .............................................................................................. 68

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List of Table

Table 4-1: Weight of water added under different degree of saturation .............................. 36

Table 4-2: Direct Shear Test Data at 30% of Degree of Saturation .................................... 36

Table 4-3: Direct Shear Test Result at 30 % Degree of Saturation ..................................... 37

Table 4-4: Direct Shear Test Result at 40 % Degree of Saturation ..................................... 38

Table 4-5: Direct Shear Test Result at 50 % Degree of Saturation ..................................... 39

Table 4-6: Direct Shear Test Result at 60 % Degree of Saturation ..................................... 40

Table 4-7: Direct Shear Test Result at 73.64 % Degree of Saturation ................................ 41

Table 4-8: Direct Shear Test Result at 80% Degree of Saturation ...................................... 42

Table 4-9: Direct Shear Test Result at 90% Degree of Saturation ...................................... 43

Table 4-10: Direct Shear Test Result at 100% Degree of Saturation .................................. 44

Table 4-11: Shear Strength Parameters Value at Different Degree of Saturation ............... 45

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List of Figure

Figure 2-1: The Great Mosque of Djenne In Mali Built in Adobe . ...................................... 6

Figure 3-1: Laboratory Investigation Program .................................................................... 17

Figure 4-1: The Relationship of Percent of Finer With Grained Size Distributions ........... 32

Figure 4-2: Liquid Limit Flow Chart ................................................................................... 33

Figure 4-3: Compaction Curve for the Investigated Soil ..................................................... 34

Figure 4-4: Shear Vs Horizontal Displacement Due to 30 % Degree of Saturation. .......... 37

Figure 4-5: Maximum Shear Vs Normal Stress Curve Due To 30 % Degree of Saturation.

...................................................................................................................................... 38

Figure 4-6: Maximum Shear Vs Normal Stress Curve Due to 40 % Degree of Saturation. 39

Figure 4-7: Maximum Shear Vs Normal Stress Curve Due to 50 % Degree of Saturation. 40

Figure 4-8: Maximum Shear Vs Normal Stress Curve Due to 60 % Degree of Saturation. 41

Figure 4-9: Maximum Shear Vs Normal Stress Curve Due to 73.64 % Degree of

Saturation. ..................................................................................................................... 42

Figure 4-10: Maximum Shear Vs Normal Stress Curve Due to 80% Degree of Saturation.

...................................................................................................................................... 43

Figure 4-11: Maximum Shear Vs Normal Stress Curve Due to 90% Degree of Saturation 44

Figure 4-12: Maximum Shear Vs Normal Stress Curve Due to 100% Degree of Saturation

...................................................................................................................................... 45

Figure 4-13: Degree of Saturation (S) Vs Cohesion (C) Relationship ................................ 46

Figure 4-14: Incremental Cohesion (C) Vs Degree of Saturation (S) Correlation graph ... 47

Figure 4-15: Decremental Cohesion (C) Vs Degree of Saturation (S) Correlation graph .. 47

Figure 4-16: Degree of Saturation (S) Vs Angle of Internal Friction (ϕ) Relationship ...... 48

Figure 4-17: Incremental Angle of Internal Friction (ϕ) Vs Degree of Saturation (S)

Correlation graph .......................................................................................................... 49

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Figure 4-18: Decremental Angle of Internal Friction (ϕ) Vs Degree of Saturation (S)

Correlation graph .......................................................................................................... 49

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List of Table (Appendix)

Table A. 1: Initial Moisture Content .................................................................................... 58

Table A. 2: Specific Gravity ................................................................................................ 58

Table A. 3: Free Swell ......................................................................................................... 59

Table A. 4: Liquid Limit ...................................................................................................... 59

Table A. 5: Compaction ....................................................................................................... 60

Table A. 6: Direct Shear Test Data at 40 % Degree of Saturation ...................................... 60

Table A. 7: Direct Shear Test Data at 50 % Degree of Saturation ...................................... 61

Table A. 8: Direct Shear Test Data at 60 % Degree of Saturation ...................................... 61

Table A. 9: Direct Shear Test Data at 73.64 % Degree of Saturation ................................. 62

Table A. 10: Direct Shear Test Data at 80 % Degree of Saturation .................................... 62

Table A. 11: Direct Shear Test Data at 90 % Degree of Saturation .................................... 63

Table A. 12: Direct Shear Test Data at 100 % Degree of Saturation .................................. 63

Table A. 13: Unified Soil Classification Systems ............................................................... 64

Table A. 14: Sieve Number and Sieve Opening ................................................................. 65

Table A. 15: Grain Size Distribution (Sieve Analysis) of Clay-Sand Mixtures Soil .......... 66

Table A. 16: Hydrometer Analysis of Clay-Sand Mixtures Soil ......................................... 66

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List of Figure (Appendix)

Figure B. 1: Shear Vs Horizontal Displacement Due To 40 % Degree of Saturation. ........ 68

Figure B. 2: Shear Vs Horizontal Displacement Due to 50 % Degree of Saturation. ......... 68

Figure B. 3: Shear Vs Horizontal Displacement Due to 60 % Degree of Saturation. ......... 69

Figure B. 4: Shear Vs Horizontal Displacement Due to 73.64 % Degree of Saturation. .... 69

Figure B. 5: Shear Vs Horizontal Displacement Due to 80 % Degree of Saturation. ......... 70

Figure B. 6: Shear Vs Horizontal Displacement Due to 90 % Degree of Saturation. ......... 70

Figure B. 7: Shear Vs Horizontal Displacement Due to 100 % Degree of Saturation. ....... 71

Figure B. 8: Sample Preparation of Clay and Sand ............................................................. 71

Figure B. 9: Liquid Limit Test Using Cone Penetration Apparatus .................................... 72

Figure B. 10: Specific Gravity, Free Swell and Hydrometer Soak...................................... 72

Figure B. 11: Sample Preparation for Compaction Test ...................................................... 73

Figure B. 12: Direct Shear Test Sample Preparation and Testing ....................................... 73

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Abstract

A series of direct shear test have been performed on a compacted clayey sands soil with

different degree of saturation to analyze the effect of degree of saturation on the shear

strength parameters of c-ϕ soil. A comprehensive research methodology was developed to

determine shear strength properties of c-ф soil in controlled degree of saturation with in

fixed void ratio and sand clay mixture based on compaction result. Clayey sands mixture

was prepared from disturbed 70% sand and 30% clay. The clay and sand sample were

collected from Gullele, Addis Ababa and Langano, near Adama. The index properties and

compaction test were conducted to figure out the properties and maximum dry densities of

the mixed soil. Also the direct shear tests were conducted by varying the degree of

saturation. The soil sample of preparation for direct shear test has sieved passing sieve no.4

and was compacted as required by ASTM D standard. The shearing displacement is

constant at 1 mm/minutes and the normal stresses are 100 kPa, 200 kPa and 400 kPa. The

investigated clay-sand mixture soil, its specific gravity was found to be 2.69 with 26%

liquid limit and categorized in non-plastic zone. The maximum dry density was found to be

1.942 g/cm3 at the optimum water content of 10.4%. The increase in degree of saturation

causes the increase in cohesion and angle of friction which is similar to the compaction

curve (Figure 4-13 and 4-16). After the optimum moisture content point as the degree of

saturation continue its increase but the cohesion and angle of internal friction decrease. The

correlations were developed to show the effect of degree of saturation on shear strength

parameters of c -ϕ soil of compacted soils.

Key words: Cohesion, internal friction angle, degree of saturation, direct shear test.

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1. Introduction

1.1 Background of problems and significance of the study

Mechanical properties of soil are necessary for the design and analysis of earth structures,

soil slope, retaining wall, soil foundation. Soil strength indicates the ability of the soil to

carry load. Direct shear testing is one of the oldest strength tests and popular is determining

shear strength of soil. The method has been standardized by the American Society for

Testing of Materials (ASTM D).

Conventional soil mechanics principles are commonly used in engineering practice

assuming soils are typically found in a state of saturated condition in nature. However,

soils typically have other fluids in the voids (e.g., air) along with water.

The variation of moisture content stored in the ground and earth structures under varying

environmental conditions is an important aspect closely related to the mechanical behavior

of partially saturated soils. Change in the degree of saturation can cause significant

changes in volume and shear strength.

The volume change properties of soils (water addition causing swelling and water removal

causing shrinkage) lead to severe management issues related to the integrity of civil

infrastructure that generally involves soil compaction. Most of the infrastructure has been

constructed on/with compacted soils. Shear strength of compacted soil is an important part

of geotechnical engineering because of the role it plays in: (i) the evaluation of bearing

capacity of foundations for residential and commercial facilities, (ii) the evaluation of

stability of the slope for highway embankments, earth dams, canals, excavations and (iii)

the design of earth retaining structures like retaining walls, sheet piles and coffer dams.

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Direct shear test device is commonly used on diameter of about 60 mm and thickness of

about 20 mm (ASTM 3080-98). The standard method has limited the maximum particle

size to one-tenth of the mould diameter or one-sixth of the mould thickness. The soil

samples however may have different degree of saturation. For soil mass with only one

degree of saturation, the obtained result of the direct shear test therefore may not truly

represent the actual in-situ properties dry and wetting season. Hence it‟s significant to

develop some relationship to understand the impact of degree of saturation. Therefore this

research has been undertaken the direct shear test on c-ϕ soil sample with different degree

of saturation.

The study investigate the effect of degree of saturation on shear strength of c-ϕ soil which

is a function of the apparent angle of internal friction and of the apparent cohesion as

evaluated by direct shear tests.

1.2 Research Objectives

The main objective of this research is to investigate the effect of degree of saturation on the

results of shear strength of compacted c-ϕ soils.

Specific objective:

To determine the shear strength parameters, i.e., - friction angle (ϕ'), and cohesion

(c') of compacted samples under different degree of saturation using direct shear

testing.

To develop some correlation between shear strength parameters and degree of

saturation (s).

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1.3 Research Methodology

This section presents a basis for a comprehensive laboratory investigation program. The

whole laboratory investigation program that would be divided into three stages:

geotechnical index properties, compaction curve and shear strength properties.

The sample of Clay and sand was obtained from Gullele, Addis Ababa and Langano, near

Adama. Geotechnical index properties would be done to determine the index properties of

investigated soil. The compaction curve of investigated soil would be done to determine

the optimum water content and maximum dry density, and to obtain the compacted sample

to investigate the behavior of compacted soil. The shear strength properties would be

determined for compacted different degree of saturation samples using consolidated drain

direct shear testing (by using perforated metal plate to let the water out). Total eight sets of

tests would be conducted before and after the optimum moisture content point based on the

compaction test result. The research will focus on understanding the shear strength

properties of compacted soils through the laboratory test and parametric study. Overall, the

output would be expected to introduce the impact of degree of saturation on the results of

direct shear tests of c-ϕ soil and a correlation to determine the cohesion and internal

friction angle with relationships of degree of saturation. Generally, the research

methodology comprises; literature review, index properties and standard proctor

compaction test, direct shear tests, determination of cohesion (c) and friction angle ϕ, and

discussions and conclusions.

1.4 Scope and limitations of the Study

Even though there are many influential properties should be studied in conjunction with

degree of saturation but due to the absence of laboratory apparatus and small budget, this

study focus only to investigate the effect of degree of saturation on the results of direct

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shear strength of c-ϕ soil using direct shear test in correlated degree of saturation with a

predetermined void ratio and sand-clay proportion.

The scope of the research include as follows.

1. Laboratory test were conducted on c-ϕ soil specimens with a fixed ration of clay

and sand mixture.

2. The collected soil samples were disturbed.

3. Determining the properties of soil, including water content, specific gravity,

Atterberge‟s limits, grained size analysis (sieve and hydrometer analysis), and

compaction test.

4. Direct shear testing using small-scale direct shear box (60x60x20mm).

5. Normal stresses used in the direct shear were 100 kPa, 200 kPa, and 400 kPa with a

constant shear displacement rate of 1 mm/minute.

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2. Literature Review

2.1 General

The influence of degree of saturation on both shear strength parameters cohesion „c‟ and

angle of internal friction „ϕ‟ is very significant. Formulating some relationship and

correlation leads to understand the effect and to express in equation and graphs. This

provides the general trends expected in direct shear tests for clay-sand mixtures of variable

degree of saturations.

In ancient civilization, in the time where there was no cement, sand and clay were used to

form brick called adobe means mud brick in Spanish which is a building material made

from earth. Even though many years were passed, there are a lot of structures exist as a

testimony which stood stand still today, like the great mosque of Djenne in Mali and Poeh

Museum tower in USA (THJ Marchand, 2016). It is still in use around the world in

southern United States and South America and Europe even in Africa. To form a good

adobe brick and other geotechnical structure like earth bag, the best ratio was mixing clay

and sand in 30 to 70 present respectively (James R. Clifton, 1979).

clay-sand mixtures were considered by design geotechnical and environmental engineers

for use as hydraulic barriers. Adding clay to the sand helps in achieving low hydraulic

conductivity. The ASTM standards classify the material as clay when the percentage of

material passing sieve no. 200 is greater than 50%, and the consistency tests indicate CL

classification. Also sand is soil that is smaller than 4.75 mm sieve and retained 0.075 mm

sieve. Direct shear test has long been used to estimate the shear strength parameters for the

analysis of slope stability, retaining wall, and bearing capacity problems. Shear strength is

the ultimate resistance force to limit damage when the soil was sheared by force, which is

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one of the most significant indicators of soil physical properties. The main effects of shear

strength are the species of soil structure, moisture content, void ratio and the amount of

sand (Li-chang Wang, 2014).

Shear strength parameters are the key parameter required in the design of foundations,

dams, retaining walls, bridge abutments, and temporary support structures. This chapter

compiles background information related to direct shear test and its result of shear strength

properties of soils due to the effect of variation of degree of saturations.

Figure 2-1: The Great Mosque of Djenne In Mali Built in Adobe (THJ Marchand, 2016).

2.2 Effect of Degree of Saturation Variation on Direct Shear Test Result

Kim (2011) studied the variation of shear strength of weathered granite soil with water

content. This study investigates the effects of initial water content and disturbance on the

strength reduction for both disturbed and undisturbed samples of weathered granite soil in

Korea using direct shear test. Several series of direct shear tests were carried out on

undisturbed or disturbed samples with various water contents under normal stress ranging

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from 30 KPa to 140 KPa. He found out that cohesion and friction angle of weathered

granite soils linearly decrease with an increase in degree of saturation.

Blazejczak et al. (1995) investigated the effect of soil water conditions and soil compaction

on the age hardening process of loamy sand and silty loamy sand in relation to the tensile

strength. Soil samples were moulded at water contents 10%, 15%, and 20% and

compacted upto1.35, 1.45, 1.55 g/cm3. At intervals after moulding, the tensile strengths of

the moist samples were measured with the indirect tension test. High water content had a

negative effect on the tensile strength of soil at constant bulk density. High bulk density,

however, had a positive effect on tensile strength at constant water content.

The Terzaghi‟s definition of effective stresses for saturated soils implies that the changes

in volume and the shear strength of a soil element are entirely due to the change in

effective stresses; in other words, shear strength and void ratio are unique functions of

effective stresses. Therefore the state of a saturated soil is considered as completely

specified by one stress state variable (total stress minus pore water stress) and a volumetric

variable (the void ratio or the water content). Since in partially saturated soils also the air

component has to be taken into account in the description of the mechanical behaviour,

additional parameters are required to describe the state of partial saturation. On the other

hand, to describe the volumetric behavior it is necessary to define a volumetric variable

that identifies the amount of total pore volume (Vv) that is occupied by water (i.e. ew = Vw

/ VS , Toll, 1995). Thus, as far as the volumetric behavior is concerned, the degree of

saturation S is considered by many authors (Gallipoli et al., 2003, Wheeler and Sivakumar,

1995, Wheeler, 1996,) the more suitable to describe the state of partial saturation since it is

related to both the water content and the void ratio by the following expression:

S = ew / e = Vw / Vv = WGs / e (2.1)

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Where W is the water content, Gs is the specific gravity and e is the void ratio.

2.3 Shear Strength for Soils

Shear strength of soils is highly affected by moisture conditions, especially if the soil

contains clay materials. Several landslides were caused by a sudden drop in the mechanical

properties of the material associated with an increase in the water content. This was the

case, for example, in the catastrophic events of the Vaiont Dam failure, where a landslide

caused sudden emptying of the reservoir (Hendron Jr.,A. J. and Patton, F. D., 1987).

An understanding of the shear strength of soil is essential in foundation engineering. This

is because most geotechnical failure involves a shear type failure of the soil. This is due to

the nature of soil, which is composed of individual soil particles that slide when the soil is

loaded. Shear strength of soil is characterized by cohesion (c), and friction angle (ϕ). The

parameters, define the soil maximum ability to resist shear stress under defined load. The

shear strength of soil is required for many different types of engineering analyses (K

Bláhová, 2013). Cohesion mobilizes at the beginning of stress conditions and reaches

maximum values around the plastic limit, i.e. at the beginning of structural collapse

(Mencl, V., 1997).

Internal friction is generally defined as resistance of two planes moving against each other,

determined by their grading. Friction increases with increase in normal load, provided that

the soil specimen is allowed to consolidate (Mencl, V., 1997). It is expected for the shear

strength to grow with the decrease in water content. This assumption is in accordance with

Toll (2000), who says that clayey materials compacted drier than optimum moisture

content behave in a coarser fashion, due to aggregation, than would be justified by the

grading. Therefore reduction of water content in clayey soils results in higher friction

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angle, due to the fact, that clay particles group into aggregates which have larger effective

particle size, as proposed in Brackley (1973, 1975).

From Terzaghi‟s definition the concept of effective stress will first be introduced. The

effective stress is defined as

(2.2)

Where,

is effective stress

is total stress and

u is pore water pressure.

In shear strength testing, the total stress acting on the soil specimen can be determined as

the load divided by the area over which it acts. The pore water pressure and the air pressure

in the soil is typically assumed to be equal to zero that is slowly sheared in direct shear

apparatus. The shear strength of soil can be defined as,

f = c + nftan

Where,

τf = shear stress on the failure plane at failure,

c' = effective cohesion,

σnf = effective normal stress on the failure plane at failure,

ϕ' = effective friction angle.

2.3.1 Friction Angle

Friction angle for a given soil is the angle on the graph (Mohr's Circle) of the shear stress

and normal effective stresses at which shear failure occurs. Friction angle of soil is

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generally denoted by "ϕ". Gravels with some sand typically have a friction angle of 34ο to

48ο , loose to dense sand have 30

ο to 45

ο, silts have a friction angle of 26

ο to 35

ο and clay

have around 20ο. Well graded soils have high values of friction angle. (Pa‟lossy et

al.,1993).

The friction angle is a function of the characteristics like particle size, compaction effort

and applied stress level (Hawley, 2001; Holtz and Kovacs, 2003). Friction angle increases

with the increase in particle size (Holtz, 1960) whereas Kirkpatrick (1965) made it more

specific by indicating that the friction angle increases as the maximum particle size

increases. Friction angle also increases with the increase in angularity and surface

roughness (Cho et al, 2006). With an increase of density or decrease in void ratio, friction

angle increases (Bishop, 1996). Bhandary and Yatabe (2007) reported that friction angle

decreased with the increasing values of expansive mineral ratio (relative amount of

expansive clay mineral to non-expansive clay mineral).

2.3.2 Cohesion

Cohesion of soil is usually denoted by "c" and is one of the important components of shear

strength soil mainly for fine materials. Cohesion is the attraction by which soil particles are

united throughout the mass. Cohesion is the strength of soil which behaves like glue that

binds the grains together. Rock has a cohesion value of 10,000 kPa, whereas silt has 75

kPa and clay has 10 to 20 kPa. Depending on the stiffness of the clay soft to high, cohesion

varies from 0 to 76 kPa. Natural minerals that have been leached into the soil, such as

caliches and salts, can provide a very strong cohesion. Heat fusion and long term

overburden pressure will tend to fuse the soil grains together, producing significant

cohesion (R. H. Chowdhury, 2013).

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2.4 Compaction Curve

In geotechnical engineering, compaction is defined as the densification of soils by the

application of mechanical energy (Holtz et al., 2011). Soil compaction is a general practice

in geotechnical engineering to construction road, dams, landfills, airfields, foundations,

hydraulic barriers, and ground improvements.

Compaction is applied to the soil, with the purpose of finding optimum water content in

order to maximize its dry density which eventually decreases long term compressibility,

increases shear strength, and sometimes reduces permeability. Proper compaction of

materials ensures the durability and stability of earthen constructions (A Maher, and L

Gucunski., 1998). A typical compaction curve presents different densification stages when

the soil is compacted with the same apparent energy input but different water contents. The

water content at the peak of the curve is called the optimum water content (OWC) and

represents the water content at which dry density is maximized for a given compaction

energy.

Several different methods are used to compact the soil in the field, such as tamping,

kneading, vibration, and static load compaction. However, laboratory tests employ the

tamping or impact compaction method using the type of equipment and methodology

developed by Proctor (1933). This is because, the test is known as the proctor test. Two

types of compaction tests are commonly used in laboratory tests, (i) The Standard Proctor

Test, and (ii) The Modified Proctor Test (WV Ping, 2003).

Zein (2000) showed that, compacted materials are highly aggregated on the dry side of

optimum moisture content, albeit aggregation does not exist on the wet of optimum and

also noted that there were no aggregations at optimum water content (and also wet of

optimum). However, the degree of aggregation increased as the water content reduced

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below optimum moisture content. At moisture contents below 70% of OWC the material

was completely aggregated with no matrix material. The effect of compaction water

content (at three points of the compaction curve: dry, OWC, and wet) on the microstructure

of Jossigny silt (the clay fraction is 34%) was studied by Delage et al. (1996). At optimum

water content, a more massive structure with less obvious aggregates occurred. The higher

density is a result of lower resistance to deformation of the aggregates, which deform and

break down more easily; reducing in particular the interaggregate pores. On the wet side,

due to hydration, the clay particles volume is much larger and forms a clay paste

surrounding the silt grains.

According to Toll (2000) fabric plays a vital role in determining the engineering behavior

of compacted soils. Clayey materials compacted dry of optimum moisture content develop

an aggregated or „packet‟ fabric. The presence of aggregations causes the soil to behave in

a coarser fashion that would be justified by the grading. For soils, compacted to degrees of

saturation of 90% and over, the material would be expected to be non-aggregated. As the

degree of saturation drops, the amount of aggregation increases rapidly and reaches a fully

aggregated condition for degrees of saturation below 50%.

2.5 Soil Classifications

Based on ASTM (D 2487 00) soil classification is the method used to purpose the soil type

and predict the soil behavior introductory. In the soil classification method is mostly used

the Unified Soil Classification System (USCS). The basic element of the USCS is the

determination of the amount and distribution of particle size larger than 0.075 mm

(retained sieve no.200) is determined by sieving and the distribution of particle size smaller

than 0.075 mm by the hydrometer analysis. For the USCS, the rocks fragments and soil

particles versus size are defined as Boulders is rock that have an average diameter greater

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than 300 mm, Cobbles is rock that is smaller than 300 mm and retained on 75 mm sieve

(USCS standard sieve), Gravel is rock or soil that is smaller than 75 mm sieve and retained

4.75 mm sieve, Sand is soil that is smaller than 4.75 mm sieve and retained 0.075 mm

sieve, Silt is the fine soil that is passing 0.075 mm sieve and larger than 0.002 mm, Clay is

the fine soil that is passing 0.075 mm sieve and smaller than 0.002 mm, It is important to

separate between the size of soil particle and the classification of the soil.

The basis of the USCS is that the engineering behavior of coarse-grained soils is based on

their grain size distributions and the engineering behavior of fine-grained soil is related to

their plasticity characteristics. The USCS summary is shown in Table A.13 (Appendix).

2.6 Direct Shear Testing

2.6.1 A History of the Direct Shear Box Test

The direct shear box test is a conceptually simple test that apparently was used for soil

testing as early as 1776 by Coulomb (Lambe & Whitman, 1969) and was featured

prominently by French engineer Alexandre Collin in 1846 (Skempton, 1984). He used a

split box, 350 mm long, in which a sample of clay 40 x 40 mm section was subjected to

double shear under a load applied by hanging weights.

In Britain, Bell (1915) made the earliest measurements who constructed a device which

was to be the prototype for subsequent developments of the shear box. Bell was the first to

carry out and publish result practical of shear tests on various types of soil (Skempton,

1958).

A simple shear box with a single plane of shear was designed in 1934, using the stress

control' principle where the load was applied in increments by progressively adding

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

weights to a pan. This required considerable care and judgment on the part of the operator

in order to ascertain the load at which failure occurred.

A modern shear box was designed by A.Casagrande at Harvard (USA) in 1932. Four years

later, Gilboy at MIT, developed a constant rate of displacement machine which applies the

'strain control' principle, using a fixed speed motor. In 1946, Bishop at imperial College

introduced the improvements of design using this principle in details. Most commercial

shear box machines are still based on the displacement control principle. These machines

provide a wide range of displacement speeds, from a few millimeters per minute to about

10000 times slower. The stress-control method has certain advantages in some long-term

tests in which increments of stress must be applied very slowly, and in tests for the study of

the effect of 'creep' under constant shear stress. However, for routine testing applications

the displacement-control method is the one now normally used.

2.6.2 Significance and Use of Direct shear Test

The direct shear test is suited to the relatively rapid determination of consolidated drained

strength properties because the drainage paths through the test specimen are short, thereby

allowing excess pore pressure to be dissipated more rapidly than with other drained stress

tests. The test can be made on all soil materials and undisturbed, remolded or compacted

materials. There is however, a limitation on maximum particle size (T Boonklung, 2013).

During the direct shear test, there is rotation of principal stresses, which may or may not

model field conditions. Moreover, failure may not occur on the weak plane since failure is

forced to occur on or near a horizontal plane at the middle of the specimen (R.F. RF.

Craig., 1992.)

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Shear stresses and displacements are non-uniformly distributed within the specimen, and

an appropriate height is not defined for calculating shear strains or any associated

engineering quantity. The slow rate of displacement provides for dissipation of excess pore

pressures, but it also permits plastic flow of soft cohesive soils (R. H. Chowdhury, 2013)

Generally, advantages of the shear box test pointed out as follows:

2.6.2.1 Advantages

1) The test is relatively quick and simple to carry out.

2) The basic principle is easily understood.

3) The principle can be extended to gravelly soils and other materials containing large

particles, which would be more expensive to test by another means.

4) Preparation of re-compacted test specimens is not difficult.

5) Friction between rocks and the angle of friction between soils and many other

engineering materials can be measured.

6) The apparatus can be used for drained tests and for the measurement of residual

shear strength by the multi-reversal process.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

3. Research Methodology

3.1 General

The laboratory testing program was focused on determination of the shear strength

properties of local c-ϕ soil in different degree of saturations. The research methodology

was divided into two parts. As a Figure 3.1 shows, in part one, index properties and

compaction curve were conducted and in part two, based on the result of geotechnical

index properties and compaction curve the direct shear test was performed.

clay-sand mixtures were prepared in proportion of 30% clay (with some slit) to 70% sand.

Sand and clay were used to form brick called adobe brick. To form a good adobe brick and

other geotechnical structure like earth bag, the best ratio was mixing clay and sand in 30 to

70 present respectively. The sample of Clay and sand was obtained from Gullele, Addis

Ababa and Langano, near Adama. These sample of clay were retrieved from a depth of 1.5

m in accordance with ASTM D1452-07a. Then samples were transported to the Ethiopian

Construction, Design and Super Vision Works geotechnical laboratory facility near to

emperial, Addis abeba.

Figure 3.1 shows the laboratory investigation program. Each of the test procedures is

described in this section whereas the test data and example calculations are given in the

Appendix.

Tests performed on investigated soil consisted of the determination of

Geotechnical index properties,

Standard proctor test,

Direct shear test.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 3-1: Laboratory Investigation Program

3.2 Geotechnical Index Properties

3.2.1 Water Content

Water content (w) is the amount of water present in the soil and is represented as

percentage. Water content was determined according to ASTM D2216-05. This test

method is determination the water (moisture) content by mass of soil, rock and similar

materials where the reduction in mass by drying is due to loss of water. This test can be

performed on disturbed and undisturbed sample. The water content (w) is the ratio,

expressed as percentage of a weight of water (ww) in a given weight of soil (ws) to the

weight of dry soil (wd). The water content test consists of determining the weight of wet

soil (ws) specimen and then drying the soil in an oven about 12 to 16 hours at a

temperature of 110 °C ± 5 °C in order to determine the weight of dry soil (wd). The loss of

mass due to drying is considered to be water. The following equation was used to

determine the water content:

( ) [( )

( )] ( )

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Where,

w = water content (%),

Mcms = mass of moisture can and moist soil,

Mcds = mass of moisture can and dry soil,

Mc = mass of moisture can

3.2.2 Specific Gravity

Specific gravity (Gs) is the ratio of the mass of soil solid to the mass of an equal volume of

distilled water at 4 ºC. The specific gravity was determined by ASTM D854-10. The test

method are cover the determination of the specific gravity of the soil solids that passing

sieve no.4. A clean and dry pycnometer was weighed to the nearest 0.01 g. Distilled water

was de-aired using the vacuum pump and that was kept overnight to remove all the air

bubbles. Then the distilled and de-aired water was added to the pycnometer up to the

calibration mark of 500 ml. The mass of pycnometer and water and temperature were

measured. Around 100g of soil was dispersed and with the distilled water soil was made to

slurry. Slurry was poured into the pycnometer and remaining soil particle was carefully

washed with spray squirt bottle to pour into the pycnometer. More water was added to

make around two third volume of the pycnometer. Then vacuum pump was connected to

the pycnomter and operated for 4 hours to remove entrapped air from the soil slurry. After

the de-airing process was completed, the pycnometer was filled with de-aired distilled

water to the calibration mark and weight of the pycnomter was measured. The soil slurry

was transferred to the evaporating dish and it was kept in an oven that maintained the

temperature at 110°C. The following relationship was used to measure the specific gravity

of investigated soil:

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To calculate the mass of the pycnometer and water at the test temperature:

( ) ( )

Where:

Mrw,t = mass of the pycnometer and water at the test temperature (Tt), g,

Mp = the average calibrated mass of the dry pycnometer, g,

Vp = the average calibrated volume of the pycnometer, mL, and

pw,t = the density of water at the test temperature (Tt), g/mL from Table 2(ASTM)

To calculate the specific gravity at soil solids the test temperature, Gt:

( ( )) (3.3)

Where:

ps = the density of the soil solids Mg/m3 or g/cm

3,

pw,t = the density of water at the test temperature (Tt), from Table 2(ASTM), g/mL

. or g/cm3.

Ms = the mass of the oven dry soil solids (g), and

Mpws,t = the mass of pycnometer, water, and soil solids at the test temperature, (Tt), g.

Finally, calculate the specific gravity of soil solids at 20°C:

(3.4)

Where:

K = the temperature coefficient given in Table 2(ASTM). Or K is the ratio of the

density of water (or t) at the test temperature t and at 20 °C.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

( )

The specific gravity of a soil solid is used in calculating the phase relationships of soils,

such as void ratio and degree of saturation.

3.2.3 Grain Size Distribution

The grain size distribution (GSD) was determined in accordance with ASTM D422-63

(2007). GSD was done in two phases. In the first phase particle sizes larger than 75 μm

(retained on the No. 200 sieve) was determined by sieve analysis and then in the second

phase the distribution of particle sizes smaller than 75μm was determined by a

sedimentation process, using a hydrometer.

3.2.3.1 Sieve Analysis

Around 500g soil specimen was taken and distilled water was added to the sample to make

it slurry. The slurry was allowed to passed through the Sieve No. 200 (opening size =

0.075 mm). The soil retained and passing from the sieve was transferred to the evaporating

dishes and kept in oven at the temperature of 110 °C ± 5 °C. The specimens were taken out

of oven after drying and weighed. The fines content (%) was calculated from retained soil.

Sieve properties following ASTM standard is shown in Table A.14 (Appendix)

3.2.3.2 Hydrometer Analysis

The finer soil, mainly the clay fraction (the percent finer than 0.002 mm) which cannot be

analyzed by sieve, is usually done by hydrometer analysis. After sieve analysis, the soil

retained on the pan was dried and around 100 g of soil was taken for the hydrometer

analysis. This sample was mixed with 125 mL of 4% NaPO3 solution in a small

evaporating dish and the dish was covered by wet paper towel to minimize evaporation.

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The mixture was kept for 16 hours to soak. After soaking, the mixture was transferred to a

dispersion cup and water was added until the cup was about two-thirds full. Then the

mixture was transferred to the sedimentation cylinder and agitated carefully for about 1

minute to make the mixture uniform. Then the cylinder was set for the hydrometer test and

first reading was taken at an elapsed time of 2 minutes. At the same time water temperature

was recorded. At least 15 seconds before the reading taken, the hydrometer was placed on

the cylinder so that it can be settled down.

Hydrometer and temperature readings were continued at approximate elapsed times of 5,

15, 30, 60, 250 and 1440 minutes. The density of the suspension at the level of hydrometer

can be computed by means of Stocks law, whereas the weight of the particles finer than

that size can be computed from the density of the suspension at the same level. The results

are represented by cumulative curve plotted on semi-logarithm graph.

3.2.4 Free Swell

Free Swell Index is the increase in volume of a soil, without any external constraints, on

submergence in water.

( )

(3.6)

Where:

Vf = final volume of soil specimen read after 24 hours from the graduated

cylinder containing distilled water.

Vi = initial volume of soil specimen read from the graduated cylinder.

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3.2.5 Atterberge‟s (Consistency) Limits

The liquid limit is the water content at which soil changes from the liquid state to a plastic

state or the minimum moisture content at which a soil flows upon application of very small

shear force. Liquid limit (wl) is the water content, in percent, of a soil at the arbitrarily

defined boundary between the semi-liquid and plastic states whereas the plastic limit (wp)

is the water content, in percent, of a soil at the boundary between the plastic and semi-solid

states.

The liquid limit, plastic limit and plasticity index were determined according to ASTM

D4318–10. The liquid limit and plastic limits are used for soil identification and

classification and for strength correlation. The specimen was processed to remove any

material retained on a 425-m (No. 40) sieve. The liquid limit was determined by

performing trials in which a portion of the specimen was spread in a brass cup, divided in

two by a grooving tool, and then allowed to flow together from the shocks caused by

repeatedly dropping the cup in a standard mechanical device. But due to the amount of

sand compared to clay was high, conducting this procedure was failed hence to determine

the liquid limit cone penetrometer was used. This is based on penetration of cone shaped

metal object into a homogeneously prepared soil mud with free fall. 300 g sample of soil is

taken and mixed with water then by pushing a portion of mixed soil into the cap with a

palette knife taking care not to trap air. Strike off excess soil with the straightedge to give a

smooth level surface. With the penetration cone locked in the raised position lower the

supporting assembly so that the tip of the cone touches the surface of the soil. When the

cone is in the correct position a slight movement of the cup will just mark the soil surface.

Lower the stem of the dial gauge to contact the cone shaft and recording of the dial gauge

to the nearest 0.1 mm in 5+1 seconds. Take a moisture content sample about 10 g from the

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

area penetrated by the cone and determine the moisture content. Repeat the step at least

three more times using the same sample of soil to which further increments of distilled

water have been added. Lastly, water content corresponding to 25 blows was determined.

(See cone penetration apparatus used for liquid limit test in appendix b)

About 20 g portion of soil was taken from the material prepared for the liquid limit test to

determine the plastic limit of soil. The water content of the soil was reduced to a

consistency at which it can be rolled without sticking to the hands by spreading on the

glass plate. The mass is rolled between the palm or fingers and the ground-glass plate with

just sufficient pressure to roll the mass into a thread of uniform diameter throughout its

length. The thread was further deformed on each stroke so that its diameter reached 3.2

mm (1/8 in). Two trials were done for plastic limit test and the average value was taken for

plastic limit.

Finally, the difference between liquid limits and plastic limits were taken as plastic index.

The study of plasticity index, in combination with liquid limit, gives information about the

type of clay. Plasticity chart, which is a plot between the plasticity index and liquid limit, is

extremely useful for classification of fine-grained soils. In fact, the main use of consistency

limits is in classification of soils.

3.3 Compaction Curve

The standard proctor compaction tests were done on the investigated soil according to

ASTM D1557-09. Total five numbers of samples have compacted to get a proper

compaction curve. Air dried sample was used for each compaction test. All the lumps of

the soil were broken and sieved through a 4.75 mm opening sieve (sieve No. 4) and collect

the entire passed sample and stored in the container. Enough water was added to the soil

sample (passed through 4.75 mm opening sieve) and mixed thoroughly to bring the water

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

content up desired quantity. Weight of the proctor mold and base plate were measured.

After attaching the mold top extension soil sample will be poured into the mold in three

equal layers. Each layer will be compacted with standard proctor compaction effort by 25

times before the next layer of loose soil was poured into the mold. After compaction of

each three layers, by removing the top extension, excess soil above the mold was trimmed.

Weight of the (proctor mold + base plate + compacted moist soil) was measured.

Compacted soil was removed from mold carefully. Small amount of soil was kept for the

water content determination after removing the sample from the mold. To determine dry

unit weight and dry density, first bulk density () was determined as follows:

( )

(3.7)

Where:

pm = moist density of compacted specimen, Mg/m3,

Mt = mass of moist specimen and mold, kg,

Mmd = mass of compaction mold, kg, and

V = volume of compaction mold, m3

To determine dry density:

(3.8)

Where:

pd = dry density of compacted specimen, Mg/m3, and

w = water content, %.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

To determine dry unit weight:

in KN/m3 (3.9)

Where:

d = dry unit weight of compacted specimen.

To calculate points for plotting the 100 % saturation curve or zero air voids curve

select values of dry unit weight, calculate corresponding values of water content

corresponding to the condition of 100 % saturation as follows:

( )( )

( )( ) (3.10)

Where:

wsat = water content for complete saturation, %,

w = unit weight of water, 9.789 kN/m3 at 20°C,

d = dry unit weight of soil, kN/m3, and

Gs = specific gravity of soil.

Soil placed as engineering fill (embankments, foundation pads, road bases) is compacted to

a dense state to obtain satisfactory engineering properties such as, shear strength.

Laboratory compaction tests provide the basis for determining the percent compaction and

water content needed to achieve the required engineering properties, and for controlling

construction to assure that the required compaction and water contents are achieved.

During design of shear or other tests require preparation of test specimens by compacting

at some water content to some unit weight. It is common practice to first determine the

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

optimum water content (wo) and maximum dry unit weight (dmax) by means of a

compaction test.

3.4 Direct Shear Test

In this study, based on the compaction result eight sets of direct shear test had conducted 3

in wetting and 4 in drying side with controlled degree of saturation in predetermine void

ratio (from maximum dry density with optimum moisture content) and c-ϕ soil proportion.

The consolidated drain test was conducted on different degree of saturation by varying the

moisture content of the samples.

Direct shear test are performed to determine the shear strength parameters of soil. The test

procedure follows the relevant ASTM standard (ASTM D3080). This test method covers

the determination of the consolidated drained shear strength of a soil material in direct

shear test. The test is performed by deforming a specimen at a controlled strain rate on or

near a single shear plane determined by the configuration of the apparatus. Generally, three

or more specimens are tested, each under a difference normal load, to determine the effect

upon shear resistance and displacement, and strength properties such as Mohr strength

envelopes. Shear stress and displacement are non-uniformly distributed within the

specimen. An appropriate height cannot be defined for calculation of shear strains.

Therefore, stress-strain relationships or any associated quantity such as modulus cannot be

defined from this test. The test condition including normal stress and moisture content are

selected by varying the degree of saturation which represent the field conditions being

investigated.

Rectangular direct shear ring was used in the shear box assembly which is 60x60x20mm

size. Normal stresses which applied are 100 kPa, 200 kPa, and 400 kPa. The shearing rate

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

is using as low speed about 1mm/minutes and 0.001376 N/div proving ring calibration,

which is the occurrence exceed pore water pressure. This test method consists of placing

the test specimen in the direct shear device, applying a predetermined normal stress,

providing for wetting or draining of the test specimens consolidating the specimen under

the normal stress, unlocking the frames that hold the test specimen, and displacing one

frame horizontally with respect to the other at a constant rate of shearing deformation and

measuring the shearing force and horizontal displacements as the specimen is sheared.

The peak strength is calculated and plotted the corresponding normal stresses with shear

strength. The test results are summarized the shear strength parameters of plotted friction

angle with water content and cohesion with water content and in relation with degree of

saturation.

To determine nominal shear stress, acting on the specimen is,

(3.11)

Where:

τ = nominal shear stress (kPa),

F = shear force (N),

A = initial area of the specimen (mm2),

Normal stress acting on the specimen is,

(3.12)

Where:

σ = normal .stress (kPa),

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

N = normal vertical force acting on the specimen (N).

3.5 Experimental Work

3.5.1 Construction of Test and Preparation of Sample

The tests were performed on disturbed compacted c-ϕ soil samples. The air-dried sand and

clay has been crushed and sieved passing sieve no.4 for the preparation of soil samples.

The physical characteristics then determined. Using conventional strain controlled direct

shear apparatus according to three classes of vertical load (100 kPa, 200 kPa and 400 kPa)

as a rapid method to determine the shear strength of soils.

The degree of saturation of the soil samples have been controlled accurately through

adjusting the amount and proportion of air- dried soil, water and sand on the experimental

study.

3.5.2 Degree of Saturation Controlled Soil Samples Preparation

There are eight soil samples have been prepared by compacting air-dried soil and the

certain amount of water to study the effects of degree of saturation on the shear strength

parameters (c, ϕ). The properties of prepared samples are as follows: void ratio e = 0.385

(from compaction test result), degree of saturation s = 30%, 40%, 50%, 60%, 73%, 80%,

90% and 100%.

The calculations of parameters of the prepared sample are as follows:

(3.13)

(3.14)

(3.15)

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

( )

( ) ( ) (3.16)

The formulas for calculating the weight of air-dried soil and the amount of water added on

air-dried soil samples based on degree of saturation are as follows:

( ) (3.17)

( )

( ) (3.18)

Note:

(3.19)

But

Where; e = void ratio, n = porosity, S = degree of saturation, w = water content, GS = the

specific gravity of soil particles, ρd = dry density, w = water density (1g/ml, or 1000kg/m3,

or 1mg/m3), Vv = volume of void, Vw = volume of water, V = Volume, mds = weight of dry

soil, w0 = water content of air-dried soil, mwo = weight of air-dried soil, mw = weight of

water and mw(add) = the additional water to be added on the sample.

3.6 Correlation of Cohesion (C) and Friction Angle (Φ) With

Degree of Saturation

Analysis of the effects of degree of saturation on the shear strength parameters (the

cohesion c, the angle of internal friction ϕ) has been worked out by using a single factor

analysis test which is a statistical method used to describe variability among observed,

correlated variables in terms of a potentially lower number of unobserved variable called

factors.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

4. Results and Discussions

4.1 General

This chapter presents and discusses the results obtained from the study. The test results

were water content, specific gravity, grained size distribution, compaction test,

Atterberge‟s limit, and direct shear strength. These are believed to be important parameters

to determine the properties of soils which are essential for the design of foundation and

other geotechnical related structures.

4.2 Geotechnical Index Properties

4.2.1 Water Content

As the soil sample was clay-sand mixtures, the initial moisture content for disturbed soil

was determined. The initial water content of 3 samples are: 1.32%, 1.21%, and 1.21%.

Accordingly, the average initial (air dried) water content is 1.25%.

4.2.2 Specific Gravity

The specific gravity relates the density of the soil particles to the density of water. The

determination of the dry mass of the soil is using a pycnometer to obtain the volume of the

soil solids (ASTM D854). Specific gravity tests carried out on 2 samples were 2.679 and

2.700. Hence, the average specific gravity is 2.69.

4.2.3 Grained size distributions

The grained size analysis is the methodology to present the grained size distributions of

soil. The relationship of percent finer with grained size distributions have plotted on the

semi-log graph as showing in Figure 4.1. The soil fabrication has containing sand 70%, silt

7% and clay 23% (from sieve and hydrometer result). Soil classification is following

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Unified Soil Classification System (USCS). According to the USCS, this soil sample group

name is clayey sands and can be classified as low plasticity (CL).

4.2.3.1 Sieve Analysis

The grain size distribution (sieve analysis) of this soil sample has been shown in Figure 4.1

below in conjunction with hydrometer analysis (Table A.15).

4.2.3.2 Hydrometer analysis

The hydrometer analysis of soil sample has been shown in Figure 4.1 in combination with

sieve analysis result (Table A.16). After sieve analysis, the soil pass to the pan was dried

and around 50 g of soil was taken for the hydrometer analysis.

Generally,

Particles larger than 2mm = 11%

Coarse Sand 2mm - 0.425mm = 50%

Fine Sand 0.425mm - 0.075mm = 9%

Silt 0.075-0.002mm = 7%

Clay smaller than 0.002mm = 23%

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-1: The Relationship of Percent of Finer With Grained Size Distributions

4.2.4 Free Swell

Free Swell Index is the increase in volume of a soil, without any external constraints,

submergence in water. The free swell indexes obtained from the test using two soil sample

were 14 % and 15 %. The average value of free swell is 14.5%.

4.2.5 Atterberge‟s (Consistency) Limits

Liquid limit obtained from the test using 300 g soil sample. From cone penetration test the

liquid limit test result was 26 % as shown in the figure 4.2. As the sand amount was 70 %,

even though there is small plasticity due to the addition of clay but the sample can‟t be

rolled with the hand on the glass plate. Hence, the plastic limit wasn‟t determined.

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

110.00

0.00100.01000.10001.000010.0000

% P

ass

Particle size(mm)

Sieve Analysis and Hydrometer Analysis Combine

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-2: Liquid Limit Flow Chart

As a general, the specific gravity of the soil was found to be 2.69. Materials finer than

0.075 mm and finer than 0.002 mm were respectively found to be 7% and 23%, thereby,

which is more dominate by sandy soil which was 70% confirming the coarse grained

nature of the soil. The clayey sands mixture had 26% liquid limit and with small plasticity

due to the addition of clay even if it was categorized in non-plastic zone. Hence, the soil

mixture was classified as CL.

4.3 Compaction Curve

Figure 4.3 shows the compaction curve for investigated soil from the result of standard

proctor compaction test. The curve consisted of the five proctor points as shown in the

figure. The maximum dry density was found to be 1.942 g/cm3 at the optimum water

content of 10.4%. The increase in d with an increase in water content on dry side of

optimum is due to expulsion of air from the pore space and re-arrangement of particles that

decreases the pore space. Conversely, an increase in water content on wet side of optimum

10.00

12.00

14.00

16.00

18.00

20.00

22.00

24.00

26.00

28.00

30.00

10 100

% M

OIS

TU

RE

NO. OF BLOWS

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

results in an increased volume of water (w = 1 g/cm3) which replaces the soil particles (Gs

= 2.69 g/cm3).

Figure 4-3: Compaction Curve for the Investigated Soil

4.4 Direct Shear Test

Even though there are many factors, the variation of degree of saturation is one of the main

factors that affect the nature of soil, which is composed of individual soil particles that

slide when the soil is loaded. Hence, understanding of the shear strength of soil is

necessary in the geotechnical engineering.

4.4.1 Shear Strength Parameters on Different Degree of Saturation.

In process of founding cohesion and internal friction angle, the first step is determining the

weight of air-dried soil and the amount of water added on air-dried soil samples based on

degree of saturation. Equation 3.17 and 3.18 are helps to determine these values.

( )

1.500

1.550

1.600

1.650

1.700

1.750

1.800

1.850

1.900

1.950

2.000

0.00 5.00 10.00 15.00 20.00

Dry

Den

sity

, g

/cc

Moisture Content, %

Moisture - Dry Density Relationship

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

( )

( )

Using equation (3.17) and (3.18), the weight of air-dried soil and the amount of water

added for preparing soil samples for conducting direct shear test under different degree of

saturation were worked out as shown in Table 4.1.

A relationship was developed from the compaction test result to fix the value of void ratio.

Therefore, at maximum dry density

– 1 = 0.385

Hence, weight of air-dried soil needed for sample preparation was,

( )

( ) ( )

The amount of water should be added to develop the desire degree of saturation was also

based on the compaction test result.

Sample calculation: to meet 40 % degree of saturation, the water content of the sample

should be,

Hence, the amount of water added become,

( )

( )

( ) ( )

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table 4-1: Weight of water added under different degree of saturation

Number

Degree of

Saturation

Water

Content

Weight of

air-dried soil

Weight of

water added

S (%) w (%) mwo (g) mw(add) (g)

1 30 4.29 141.59 4.25

2 40 5.72 141.59 6.25

3 50 7.16 141.59 8.26

4 60 8.59 141.59 10.26

5 73.64 10.54 141.59 12.99

6 80 11.45 141.59 14.26

7 90 12.88 141.59 16.26

8 100 14.31 141.59 18.26

The shear strength parameters were determined from the graph of normal stress verses

shear stress and other direct shear test results were found by plotting the shear stresses with

shear displacement. Therefore, based on the effect of degree of saturation the cohesion and

the internal friction angle were determined.

Table 4-2: Direct Shear Test Data at 30% of Degree of Saturation

0.01

0.001376 0.004

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 143 54.66 25 0.25 192 73.39 25 0.25 311 118.87

50 0.5 177 67.65 50 0.5 350 133.78 50 0.5 500 191.11

75 0.75 205 78.36 75 0.75 478 182.70 75 0.75 675 258.00

100 1 231 88.29 100 1 573 219.01 100 1 784 299.66

150 1.5 252 96.32 150 1.5 601 229.72 150 1.5 936 357.76

200 2 265 101.29 200 2 588 224.75 200 2 989 378.02

250 2.5 272 103.96 250 2.5 560 214.04 250 2.5 971 371.14

300 3 261 99.76 300 3 300 3 947 361.96

350 3.5 245 93.64 350 3.5 350 3.5

Proving Ring

Calibration,KN/Div

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

For 100KPa Horizontal displacement

Readingh ,div

Specimen X-sectional Area,m2

30 % SATURATION SHEAR DATA

Horizontal dial reading corection

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table 4-3: Direct Shear Test Result at 30 % Degree of Saturation

Figure 4-4: Shear Vs Horizontal Displacement Due to 30 % Degree of Saturation.

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 103.96 229.72 378.02 29.43 40.94

30 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-5: Maximum Shear Vs Normal Stress Curve Due To 30 % Degree of Saturation.

Table 4-4: Direct Shear Test Result at 40 % Degree of Saturation

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 114.28 221.69 384.90 32.68 41.32

40 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-6: Maximum Shear Vs Normal Stress Curve Due to 40 % Degree of Saturation.

Table 4-5: Direct Shear Test Result at 50 % Degree of Saturation

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 118.11 227.80 390.63 36.69 41.45

50 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-7: Maximum Shear Vs Normal Stress Curve Due to 50 % Degree of Saturation.

Table 4-6: Direct Shear Test Result at 60 % Degree of Saturation

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 122.69 237.36 400.19 41.28 41.83

60 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-8: Maximum Shear Vs Normal Stress Curve Due to 60 % Degree of Saturation.

Table 4-7: Direct Shear Test Result at 73.64 % Degree of Saturation

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 126.52 245.00 407.07 45.48 42.02

73.64 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-9: Maximum Shear Vs Normal Stress Curve Due to 73.64 % Degree of

Saturation.

Table 4-8: Direct Shear Test Result at 80% Degree of Saturation

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 129.19 228.95 402.10 42.62 41.93

80 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-10: Maximum Shear Vs Normal Stress Curve Due to 80% Degree of Saturation.

Table 4-9: Direct Shear Test Result at 90% Degree of Saturation

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 122.69 197.61 366.55 38.22 39.37

90 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-11: Maximum Shear Vs Normal Stress Curve Due to 90% Degree of Saturation

Table 4-10: Direct Shear Test Result at 100% Degree of Saturation

Sample No. 1

Sample Condition DISTURBED

Specimen Size (mm) 60 × 60 × 20

Initial Volume (cm3) 72.00

Normal Stress (KPa) 100 200 400 C(KPa) φ (Degrees)

Shear Stress (KPa) 110.84 193.02 347.44 33.64 38.11

100 % SATURATION SHEAR RESULT

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-12: Maximum Shear Vs Normal Stress Curve Due to 100% Degree of Saturation

4.4.2 Relationships between Cohesion (c), Angle of Internal Friction (ϕ) and

Degree of Saturation (S)

The shear strength parameters cohesion (c) and angle of internal friction (ϕ) of soil samples

have been obtained by the shear strength tests of compacted c-ϕ soil.

Table 4-11: Shear Strength Parameters Value at Different Degree of Saturation

Number

Degree of

Saturation

Angle of Internal

Friction (ϕ) Cohesion (c)

S (%) (Degrees) (KPa)

1 30 40.94 29.43

2 40 41.32 32.68

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

3 50 41.45 36.69

4 60 41.83 41.28

5 73.64 42.02 45.48

6 80 41.93 42.62

7 90 39.37 38.22

8 100 38.11 33.64

4.4.2.1 Correlation between degree of saturation (s) and cohesion (c)

Figure 4-13: Degree of Saturation (S) Vs Cohesion (C) Relationship

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-14: Incremental Cohesion (C) Vs Degree of Saturation (S) Correlation graph

Hence, the correlative equation between incremental cohesion and degree of saturation is:

( ) (4.1)

Figure 4-15: Decremental Cohesion (C) Vs Degree of Saturation (S) Correlation graph

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Hence, the correlative equation between decremental cohesion and degree of saturation is:

( ) (4.2)

4.4.2.2 Correlation between Degree of Saturation (s) and Angle of Internal Friction

(ϕ)

Figure 4-16: Degree of Saturation (S) Vs Angle of Internal Friction (ϕ) Relationship

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure 4-17: Incremental Angle of Internal Friction (ϕ) Vs Degree of Saturation (S)

Correlation graph

Hence, the correlative equation between angle of internal friction (ϕ) and degree of

saturation is:

( ) (4.3)

Figure 4-18: Decremental Angle of Internal Friction (ϕ) Vs Degree of Saturation (S)

Correlation graph

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Hence, the correlative equation between angle of internal friction (ϕ) and degree of

saturation is:

( ) (4.4)

4.4.3 Analysis of the Effects of Degree of Saturation on the Cohesion (c)

Fig. 4.13 gives the relationship between cohesion and degree of saturation. The cohesion

increase with increase of degree of saturation similar to the shape of the compaction curve,

after the point where maximum dry density attained with optimum moisture content, even

though the degree of saturation increase but the value of cohesion decrease.

Cohesion was found lower at the drier side of optimum due to the presence of clay

aggregate which made the soil mass more granular. Then cohesion value increases with the

water content and reached maximum value at around optimum due to reduction of the size

of clay aggregate. This is similar to the work done by Cokca et al. (2004). They mentioned

that the cohesion at the drier side of optimum will be lesser than that at optimum water

content due to the „clay aggregation‟ phenomenon where the soil mass exhibits a granular

texture.

Increase in water content above optimum moisture content reduced cohesion as excess

water might develop thicker water film around the clay particle and thus increased the

distance between particles. Seed et al. (1961) observed that cohesion on the wetter side of

optimum is lesser than that at optimum water content due to the formation of thicker water

films‟ around clay particles in the „clay-water system‟.

4.4.4 Analysis of the Effects of Moisture Content on the Angle of Internal

Friction (Φ)

Fig. 4.16 shows the relationship between internal friction angle and degree of saturation.

As it shows, there is a slight variation which is less than 5°. The internal friction angle

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

increase with increase of degree of saturation until 73.64% of degree of saturation and

decrease as degree of saturation continue its increase.

On the dry side of optimum, the values of friction angle are not much varied with respect

to the maximum friction angle; this is due to clay aggregates formed on the dry side of

optimum (Cokca et al., 2004). The granular structure and large size of aggregates within

soil mass increased the interlocking between the particles and this generates a resistance to

slippage at the contacts between the particles (or aggregates) as the moisture content

decreases on the dry of optimum.

On the wet side of the optimum; the reduction was due to the increased lubrication of the

soil paste following water addition causing soil particles to slip and slide, resulting in a

reduced friction angle. For higher water content, the soil particles dominated the behaviour

of the soil mixture and the water acts as a lubricant, which decreases the friction angle as

the degree of saturation increases. The lubrication occurs when the surface of the soil

particle is wetted, causing the mobility of the absorbed film to increase due to increased

thickness and greater surface ion hydration and dissociation (Mitchell, 1993).

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

5. Summary, Conclusions and Recommendation

5.1 Summary

The purpose of this project work was to explore the effect of degree of saturation on the

shear strength parameters of c-ф soil by using direct shear test and to establish a clear

understanding of the shear strength behavior of compacted clayey sands mixture. The

result of direct shear tests has been discussed on the previous chapter.

A clay-sand mixture was considered by design geotechnical and environmental engineers

for use as hydraulic barriers. Adding clay to the sand helps in achieving low hydraulic

conductivity. Most geotechnical structures (like, earth bag and adobe brick) mixing 30%

clay with 70% sand were best ratio. The variation of degree of saturation in this clayey

sands mixture affects cohesion and internal friction angle. This study shows the effect of

degree of saturation on cohesion and internal friction angle.

A comprehensive research methodology was developed to determine shear strength

properties of c-ф soil in controlled degree of saturation with in fixed void ratio and sand

clay mixture. Hence, a relationship was developed between shear strength parameters (c,

υ) of disturbed compacted clayey sands and degree of saturation (s).

5.2 Conclusion

From the results and discussions presented earlier, following conclusions are drawn:

The investigated clay-sand mixture soil, it‟s specific gravity was found to be 2.69 and a

materials finer than 0.075 mm and finer than 0.002 mm were respectively found to be 7%

and 23%, thereby, which is more dominate by sandy soil which was 70% confirming the

coarse grained nature of the soil. This clayey sands mixture had 26% liquid limit and with

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

small plasticity even if the category lays in none plastic. The maximum dry density was

found to be 1.942 g/cm3 at the optimum water content of 10.4%.

The cohesion (c) followed the compaction curve with a maximum value of 45.48 kPa at the

optimum water content. The cohesion increase with increase of degree of saturation, after

the point where maximum dry density attained with optimum moisture content, even

though the degree of saturation increase but the value of cohesion decrease.

Likewise, the friction angle increase with increase of degree of saturation until 73.64% of

degree of saturation and decrease as degree of saturation continue its increase.

Even though the soil mixture would exhibit properties as discussed in discussion part, but

the shear strength test shows the compacted mixed clayey sands soil (like, Adobe brick)

wouldn‟t much affected due to the saturation. This is why the structures which were

constructed in ancient time still exist.

During the degree of saturation variation, the cohesive values much more vary than the

values of friction angle. This shows the clay with optimum water content create more

strong bonding that increase the cohesion force between the particles. Hence, this made the

material and the structure stable and strong.

5.3 Recommendation

Suction controlled direct shear test is highly recommended for accurate measurement of

friction angle due to suction.

Large-scale direct shear test should be performed on the disturbed sample at various

gradations to understand the actual situation.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Other shear strength properties test such as unconfined compression and triaxial test should

be conducted in addition to direct shear test, for more satisfactory and acceptable result and

comparison.

As the shear strength parameters are the key parameter required in the design of

foundations, dams, retaining walls, bridge abutments, temporary support and earth

structures, but degree of saturation is not the only effects of shear strength. Therefore, the

study should be broad to include the effects of the species of soil structure, void ratio and

the amount of sand proportion.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

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49(2): 143-159.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Wu, P., and Matsushima, K., and Tatsuoka, F. (2008). Effects of Specimen Size and Some

Other Factors on the Strength and Deformation of Granular Soil in Direct Shear

Tests. Geotechnical Testing Journal. Vol. 31, No.1.

Yazdanjou, V., and Eshkevari, S. N., and Hamidi, A. (2008). Effect of Gravel Content

on the Shear Behavior of Sandy Soils. The 4th National Conference on Civil

Engineering, University of Tehran.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Appendices

Appendix A: List of Table

Table A. 1: Initial Moisture Content

INITIAL WATER CONTENT TEST METHOD: ASTM D854-10

Initial Water Content

Tare Tare + Wet Tare +

Dry Dry Soil Water Moisture

Sample Mass Soil Mass Soil Mass Mass Mass Content

Tare No. (g) (g) (g) (g) (g) (%)

355 14.88 34.88 34.62 19.74 0.26 1.32

357 14.84 34.84 34.6 19.76 0.24 1.21

367 15.42 35.42 35.18 19.76 0.24 1.21

Table A. 2: Specific Gravity

SPECIFIC GRAVITY TEST METHOD: ASTM D854-10

Specific Gravity of Soil Solids

Soil Description: Temperature Density Correction

Test Number 1 2 (C) (g/ml) Factor

Volumetric Flaskj No. R C

Mass of Flask, Mf (g) 596.4 598.5

Mass of Flask + Soil, Mfs (g) 696.4 698.5

Mass of Soil, Ms (g) 100 100

With water level with the fill line:

Mass of Flask + Water + Soil (g) 1725.2 1727.6

Temperature, T (oC) 19 19 19 0.9984 1.0002

Mass of Flask + Water, Mfw (g) 1662.6 1664.7

(Mfw - (Mfws - Ms)) (g) 37.4 37.1

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Gs (at T) =

[Ms/(Mfw - (Mfws - Ms)) 2.6738 2.69542

Correction Factor 1.002 1.002

Gs (at 20 C) 2.67914 2.70081

Average 2.69

Table A. 3: Free Swell

Initial Free Swell

Sample, ml 10

No.

Free

Swell

Final

Reading

Free

Swell

(ml) %

1 11.4 14.00

2 11.5 15.00

Average 14.50

Table A. 4: Liquid Limit

LIQUID LIMIT

TEST METHOD: ASTM D4318–10

Liquid Limit Test

Trial 1 Trial 2 Trial 3 Trial 4

No. of Blows N 24.9 20.6 17.3 13.6

Mass of moist Sample + Can M1 32.91 31.12 33.01 26.69

Mass of Dried Sample + Can M2 29.17 27.99 29.82 24.73

Mass of Can Mc 14.88 14.9 15 14.77

Mass of Moist Mm=M1-M2 3.74 3.13 3.19 1.96

Mass of Dried Sample Md=M2-Mc 14.29 13.09 14.82 9.96

Moisture w = (Mm-Md) / Md x 100 26.17 23.91 21.52 19.68

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table A. 5: Compaction

COMPACTION (standard) TEST METHOD: ASTM D1557-09

MOISTURE - DENSITY RELATION OF SOIL

Standard (ASTM D1557-09)

No. of blows : 25 Weight of hammer,kg : 2.5

No. of layers : 3 Volume of mold,cm3 : 944

Trial 1 2 3 4 5

Wt. of Mold + Wet

Soil gram 6048.30 6137.30 6223.70 6013.10 5778.90

Wt. of Mold gram 4197.80

Wt. Wet Soil gram 1850.50 1939.50 2025.90 1815.30 1581.10

Volume of Mold cu.cm. 944.00

Wet Density gr/cu.cm. 1.96 2.05 2.15 1.92 1.67

Container No. 365 348 345 352 327

Wt. Cont + Wet soil grams 117.10 83.10 85.30 86.60 93.20

Wt. Cont + Dry soil grams 103.25 75.01 78.58 81.86 89.08

Weight of Water grams 13.85 8.09 6.72 4.74 4.12

Weight of Container grams 15.20 14.80 14.80 14.90 15.10

Weight of Dry Soil grams 88.05 60.21 63.78 66.96 73.98

Moisture Content % 15.73 13.44 10.54 7.08 5.57

Dry Density gr/cu.cm. 1.694 1.811 1.942 1.796 1.587

Table A. 6: Direct Shear Test Data at 40 % Degree of Saturation

0.01

0.001376 0.0036

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 153 58.48 25 0.25 200 76.44 25 0.25 496 189.58

50 0.5 217 82.94 50 0.5 349 133.40 50 0.5 688 262.97

75 0.75 256 97.85 75 0.75 453 173.15 75 0.75 807 308.45

100 1 291 111.23 100 1 532 203.34 100 1 889 339.80

150 1.5 299 114.28 150 1.5 580 221.69 150 1.5 983 375.72

200 2 295 112.76 200 2 560 214.04 200 2 1007 384.90

250 2.5 286 109.32 250 2.5 506 193.40 250 2.5 968 369.99

300 3 300 3 300 3 939 358.91

Proving Ring

Calibration,KN/Div

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

Specimen X-sectional Area,m2

40 % SATURATION SHEAR DATA

Horizontal dial reading corection

For 100KPa

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table A. 7: Direct Shear Test Data at 50 % Degree of Saturation

Table A. 8: Direct Shear Test Data at 60 % Degree of Saturation

0.01

0.001376 0.004

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 157 60.01 25 0.25 225 86.00 25 0.25 635 242.71

50 0.5 209 79.88 50 0.5 327 124.99 50 0.5 793 303.10

75 0.75 246 94.03 75 0.75 400 152.89 75 0.75 891 340.56

100 1 275 105.11 100 1 474 181.17 100 1 955 365.02

150 1.5 298 113.90 150 1.5 533 203.72 150 1.5 1007 384.90

200 2 309 118.11 200 2 596 227.80 200 2 1022 390.63

250 2.5 297 113.52 250 2.5 572 218.63 250 2.5 1009 385.66

300 3 269 102.82 300 3 550 210.22 300 3 987 377.25

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

For 100KPa Horizontal displacement

Readingh ,div

Proving Ring

Calibration,KN/Div

Specimen X-sectional Area,m2

50 % SATURATION SHEAR DATA

Horizontal dial reading corection

0.01

0.001376 0.004

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 139 53.13 25 0.25 195 74.53 25 0.25 510 194.93

50 0.5 204 77.97 50 0.5 318 121.55 50 0.5 709 271.00

75 0.75 243 92.88 75 0.75 399 152.51 75 0.75 837 319.92

100 1 274 104.73 100 1 472 180.41 100 1 929 355.08

150 1.5 302 115.43 150 1.5 565 215.96 150 1.5 1025 391.78

200 2 321 122.69 200 2 610 233.16 200 2 1047 400.19

250 2.5 308 117.72 250 2.5 621 237.36 250 2.5 1034 395.22

300 3 287 109.70 300 3 613 234.30 300 3 993 379.55

350 3.5 350 3.5 592 226.28 350 3.5

60 % SATURATION SHEAR DATA

Horizontal dial reading corection

Horizontal displacement

Readingh ,div

Specimen X-sectional Area,m2

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

For 100KPa

Proving Ring

Calibration,KN/Div

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table A. 9: Direct Shear Test Data at 73.64 % Degree of Saturation

Table A. 10: Direct Shear Test Data at 80 % Degree of Saturation

0.01

0.001376 0.0036

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 137 52.36 25 0.25 157 60.01 25 0.25 285 108.93

50 0.5 204 77.97 50 0.5 225 86.00 50 0.5 425 162.44

75 0.75 248 94.79 75 0.75 330 126.13 75 0.75 600 229.33

100 1 281 107.40 100 1 400 152.89 100 1 723 276.35

150 1.5 318 121.55 150 1.5 503 192.26 150 1.5 881 336.74

200 2 327 124.99 200 2 580 221.69 200 2 984 376.11

250 2.5 331 126.52 250 2.5 615 235.07 250 2.5 1052 402.10

300 3 325 124.22 300 3 629 240.42 300 3 1065 407.07

350 3.5 310 118.49 350 3.5 641 245.00 350 3.5 1034 395.22

400 4 0.00 400 4 634 242.33 400 4 993 379.55

450 4.5 0.00 450 4.5 624 238.51 450 4.5 964 368.46

73.64 % SATURATION SHEAR DATA

Horizontal dial reading corection

Horizontal displacement

Readingh ,div

Specimen X-sectional Area,m2

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

For 100KPa

Proving Ring

Calibration,KN/Div

0.01

0.001376 0.004

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 59 22.55 25 0.25 124 47.40 25 0.25 305 116.58

50 0.5 108 41.28 50 0.5 223 85.24 50 0.5 440 168.18

75 0.75 144 55.04 75 0.75 288 110.08 75 0.75 557 212.90

100 1 185 70.71 100 1 337 128.81 100 1 645 246.53

150 1.5 225 86.00 150 1.5 434 165.88 150 1.5 834 318.77

200 2 271 103.58 200 2 503 192.26 200 2 961 367.32

250 2.5 303 115.81 250 2.5 555 212.13 250 2.5 1035 395.60

300 3 321 122.69 300 3 586 223.98 300 3 1052 402.10

350 3.5 333 127.28 350 3.5 593 226.66 350 3.5 1047 400.19

400 4 338 129.19 400 4 599 228.95 400 4 1031 394.07

450 4.5 332 126.90 450 4.5 585 223.60 450 4.5

500 5 315 120.40 500 5 569 217.48 500 5

80 % SATURATION SHEAR DATA

Horizontal dial reading corection

Horizontal displacement

Readingh ,div

Specimen X-sectional Area,m2

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

For 100KPa

Proving Ring

Calibration,KN/Div

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table A. 11: Direct Shear Test Data at 90 % Degree of Saturation

Table A. 12: Direct Shear Test Data at 100 % Degree of Saturation

0.01

0.001376 0.004

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 50 19.11 25 0.25 75 28.67 25 0.25 288 110.08

50 0.5 87 33.25 50 0.5 121 46.25 50 0.5 399 152.51

75 0.75 120 45.87 75 0.75 167 63.83 75 0.75 486 185.76

100 1 144 55.04 100 1 200 76.44 100 1 560 214.04

150 1.5 195 74.53 150 1.5 269 102.82 150 1.5 687 262.59

200 2 232 88.68 200 2 333 127.28 200 2 797 304.63

250 2.5 263 100.52 250 2.5 387 147.92 250 2.5 865 330.62

300 3 288 110.08 300 3 419 160.15 300 3 917 350.50

350 3.5 304 116.20 350 3.5 447 170.85 350 3.5 948 362.35

400 4 314 120.02 400 4 475 181.56 400 4 959 366.55

450 4.5 321 122.69 450 4.5 492 188.05 450 4.5 951 363.49

500 5 319 121.93 500 5 508 194.17 500 5 933 356.61

550 5.5 315 120.40 550 5.5 517 197.61 550 5.5

600 6 308 117.72 600 6 511 195.32 600 6

650 6.5 650 6.5 493 188.44 650 6.5

90 % SATURATION SHEAR DATA

Horizontal dial reading corection

Horizontal displacement

Readingh ,div

Specimen X-sectional Area,m2

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

For 100KPa

Proving Ring

Calibration,KN/Div

0.01

0.001376 0.004

in Div in Kpa in Div in Kpa in Div in Kpa

0 0 0 0.00 0 0 0 0.00 0 0 0 0.00

25 0.25 33 12.61 25 0.25 73 27.90 25 0.25 266 101.67

50 0.5 52 19.88 50 0.5 122 46.63 50 0.5 341 130.34

75 0.75 71 27.14 75 0.75 163 62.30 75 0.75 416 159.00

100 1 88 33.64 100 1 197 75.30 100 1 473 180.79

150 1.5 117 44.72 150 1.5 242 92.50 150 1.5 590 225.51

200 2 144 55.04 200 2 311 118.87 200 2 680 259.91

250 2.5 165 63.07 250 2.5 365 139.51 250 2.5 770 294.31

300 3 186 71.09 300 3 415 158.62 300 3 825 315.33

350 3.5 205 78.36 350 3.5 453 173.15 350 3.5 865 330.62

400 4 217 82.94 400 4 479 183.08 400 4 884 337.88

450 4.5 226 86.38 450 4.5 492 188.05 450 4.5 902 344.76

500 5 239 91.35 500 5 501 191.49 500 5 909 347.44

550 5.5 251 95.94 550 5.5 505 193.02 550 5.5 905 345.91

600 6 261 99.76 600 6 502 191.88 600 6 898 343.24

650 6.5 273 104.35 650 6.5 489 186.91 650 6.5 881 336.74

700 7 245 93.64 700 7 471 180.03 700 7

750 7.5 281 107.40 750 7.5 750 7.5

800 8 286 109.32 800 8 800 8

850 8.5 290 110.84 850 8.5 850 8.5

900 9 285 108.93 900 9 900 9

950 9.5 278 106.26 950 9.5 950 9.5

For 200KPa For 400KPaHorizontal displacement

Readingh ,div

Horizontal displacement

Readingh ,div

For 100KPa

Specimen X-sectional Area,m2Proving Ring

Calibration,KN/Div

100 % SATURATION SHEAR DATA

Horizontal dial reading corection

Horizontal displacement

Readingh ,div

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table A. 13: Unified Soil Classification Systems

More than 12 

percent fines*

Silty gravels, gravel –sand-

silt mixturesGM

Minus no.40 soil

plots on or above the

A line

Minus no.40 soil

plots below the A

line

Does not meet Cu

and/or Cc criteria

listed above

Less than 5 pe

rcent fines*GP

Less than 5 

percent fines*Cu ≥ 6 and 1≤ Cc ≤ 3

Sands (50 percent

of more of coarse

fraction passes

no.4 sieve)

SP

SW

GCClayey gravels, gravel-sand-

clay mixtures.

More than 12 

percent fines*

Silty sands, sand-silt mixturesSMMore than 12 

percent fines*

Minus no.40 soil

plots below the A

line

Less than 5 

percent fines*

Poorly graded sands or

gravelly sands, little or no

fines

Does not meet Cu

and/or Cc criterialist

ed above

Well-

graded sands or gravelly

sands, little or no fines

Fine-grained soil

(50 percent or

more passes

no.200 sieve)

Coarse-grained

soils (More than

50 percent

retained on

no.200 sieve)

USCS

symbol

Gravels (More

than 50 percent of

coarse fraction

retained on no.4

sieve)

GW

Poorly    graded    gravels    

or gravelly sands, little or no

fines

Well-graded gravel-sand

mixtures, little or no fines

Less than 5 pe

rcent fines*

Major divisions Subdivisions Typical names Laboratory classification criteria

Cu ≥ 4 and 1≤ Cc ≤ 3

SCClayey sands, sand-clay

mixtures

More than 12 

percent fines*

Minus no.40 soil

plots on or above the

A line

Silt and clays

(liquid limit 50 or

more)

Silt and clays

(liquid limit less

than 50)

Inorganic silt, rock flour, 

silts of low plasticity

Inorganic soilPI > 7 and plots on

or above A line

LL (Oven-dried)/LL

(not dried) < 0.75

Plots below A line

PI < 4 or plots below

A line

LL (oven-dried)/LL

(not dried) < 0.75OH

Organic silts and organicclay

s of high plasticity

Plots on or above A

line

Organic silts and organic

clays of low plasticity

Inorganic clays of low

plasticity, gravelly clays,

sandy clays, etc.

CL

MH Inorganic soil

CH Inorganic soil

Inorganic silts, micaceous

silts of high plasticity

Inorganic highly plastic clays

, fat clays, silty clays, etc.

ML Inorganic soil

OL Organic

Organic

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Table A. 14: Sieve Number and Sieve Opening

No. Sieve no. Sieve opening (mm)

1 ¾ in 19.000

2 3/8 in 9.500

3 4 4.750

4 10 2.000

5 20 0.850

6 40 0.425

7 60 0.250

8 140 0.106

9 200 0.075

10 Pan -

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Table A. 15: Grain Size Distribution (Sieve Analysis) of Clay-Sand Mixtures Soil

SIEVE ANALYSIS

Group:

Soil Description:

Dry Sample Mass: (g)

Sieve

Size

#

Sieve

Opening

(mm)

Pan

Mass

(g)

Retained

Soil + Pan

(g)

Soil

Mass

(g)

%

Mass

Retained

%

Cumulative

Retained

%

Finer

4 4.75 483.700 0.000 0.0 0.0% 0.0% 100.0%

10 2.0 470.0 523.700 53.70 10.8% 10.8% 89.2%

20 0.850 436.300 569.900 133.60 26.9% 37.7% 62.3%

40 0.425 420.200 537.400 117.20 23.6% 61.3% 38.7%

60 0.250 381.000 405.100 24.10 4.8% 66.1% 33.9%

140 0.106 297.600 312.100 14.50 2.9% 69.0% 31.0%

200 0.075 333.200 337.200 4.00 0.8% 69.8% 30.2%

PAN - 515.600 665.600 150.00 30.2% 100.0% 0.0%

Total Soil Mass Sieved: 497.1

% Loss During Sieve Analysis: 2.9

D10: 0.00101 mm

D30: 0.00745 mm

D60: 0.80000 mm

Cu: 792.08

Cc: 9.22

Table A. 16: Hydrometer Analysis of Clay-Sand Mixtures Soil

Hydrometer Analysis Data

Specific Gravity = 2.69

Time (min.)

Actual

Hydr.m.

Reading

Temp.

Corrected

H.Reading Corr.

Factor

(a)

Effe.

Depth of

Hydrm.

(L)

Values

of K

Diameter

of soil

Particle

(mm)

%

finer,

D R' R"

2 19 19 20.85 14.85 0.9910 13.20 0.01365 0.0351

29.54

5 18.5 19 20.35 14.35 0.9910 13.25 0.01365 0.0222

28.55

15 18.25 19 20.1 14.1 0.9910 13.75 0.01365 0.0131

28.05

30 18 19 19.85 13.85 0.9910 13.30 0.01365 0.0091

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

27.55

60 17.5 19 19.35 13.35 0.9910 13.40 0.01365 0.0065

26.56

250 17 19 18.85 12.85 0.9910 13.50 0.01365 0.0032

25.56

1440 15 19 16.85 10.85 0.9910 13.80 0.01365 0.0013

21.58

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Appendix B: List of Figure

Figure B. 1: Shear Vs Horizontal Displacement Due To 40 % Degree of Saturation.

Figure B. 2: Shear Vs Horizontal Displacement Due to 50 % Degree of Saturation.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure B. 3: Shear Vs Horizontal Displacement Due to 60 % Degree of Saturation.

Figure B. 4: Shear Vs Horizontal Displacement Due to 73.64 % Degree of Saturation.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure B. 5: Shear Vs Horizontal Displacement Due to 80 % Degree of Saturation.

Figure B. 6: Shear Vs Horizontal Displacement Due to 90 % Degree of Saturation.

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure B. 7: Shear Vs Horizontal Displacement Due to 100 % Degree of Saturation.

Figure B. 8: Sample Preparation of Clay and Sand

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The Effect of Degree of Saturation…… Summary, Conclusions and Recommendation

Figure B. 9: Liquid Limit Test Using Cone Penetration Apparatus

Figure B. 10: Specific Gravity, Free Swell and Hydrometer Soak

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Figure B. 11: Sample Preparation for Compaction Test

Figure B. 12: Direct Shear Test Sample Preparation and Testing