STRENGTH OF KAOLIN STABILIZED WITH VARIOUS PERCENTAGE OF

LIME AND 4% SILICA FUME

MOHAMMAD SYAFIQ BIN IDERIS

A thesis submitted in fulfilment the requirements for the award of the degree of

B. ENG. (HONS.) OF CIVIL ENGINEERING

Faculty of Civil Engineering & Earth Resources

UNIVERSITI MALAYSIA PAHANG

JUNE 2015

vi

ABSTRACT

Clay soil as known as soft soil present difficulties to geotechnical engineer due to its

complex nature and also contain variable materials. This type of soil can be categorized

as problematic soil due to its weak properties. As the preliminary stage, soft clay soil

did not meet the requirement for construction purpose. This is because the entire load

from the top of the building will be transferred to the underlying soil. As we know the

strength of soil is weak, without proper design, modification and earthwork,

construction problem such as cracking, settlement of building may be occur and the

building may collapse within its design life. It is very risky if the construction is still

continuing on this type of soil without any remediation or improvement on the soil

itself. Therefore, a proper modification for the soil itself is required to alter the soil

become stronger; hence meet the requirement to use in construction industry. There are

various methods to improve the soil. This research proposes about soil stabilization

method that is soft clay soil Kaolin S300 stabilized with various percentages of lime and

4% silica fume. Percentages of lime used are 3%,5%,7% and 9%. While the percentage

of silica fume used is fixed that is 4%. The main objectives in this research is to conduct

the improvement of undrained shear strength of soft clay soil mixed with various

percentages of lime and 4% silica fume. The improvement will be observed based on

different percentage of lime. Other physical and mechanical tests that involves in this

study are Atterberg Limit, Falling Head, Standard Compaction, Hydrometer, and

Specific Gravity, The properties of soil was compared between the kaolin only and

different percentages of lime mixed with 4% silica fume. The main test in this research

is unconfined compressive test that is to determine the undrained shear strength. From

the study, the optimum amount value of lime is 5%. This is because at 5% lime content,

the maximum stress achieve is 29.37 kPa which is optimum compared to others

percentage. It is shown that, the strength of soft clay is improved by 14.28%. Based on

laboratory test result, it can be concluded that soil stabilization by using lime and silica

fume can improved the strength of soft clay. Lastly, after all the tests had been done,

correlation equation and cohesion value for each test were list out in graph and tabular

form as well.

.

vii

ABSTRAK

Tanah liat yang juga dikenali sebagai tanah lembut mendatangkan banyak masalah

kepada jurutera geoteknik berikutan sifat semulajadinya yang unik dan mengandungi

pelbagai bahan asli di dalam tanah tersebut. Tanah lembut ini dapat dikategorikan

sebagai tanah yang banyak mendatangkan masalah disebabkan sifat semulajadinya yang

lemah. Sebagai permulaan, tanah lembut ini tidak memenuhi kriteria dan syarat untuk

digunakan dalam industri pembinaan. Ini disebabkan, seluruh beban dari atas bangunan

akan dipindahkan kepada permukaan bawah tanah. Seperti yang kita tahu, kekuatan

tanah itu sangat lemah. Oleh yang demikian, tanpa kerja tanah, reka bentuk dan

modifikasi, masalah pembinaan akan berlaku sebagai contohnya keretakan, dan juga

pemendapan bangunan ke dalam tanah. Secara tidak langsung akan menyebabkan

sesuatu bangunan itu untuk runtuh lebih awal daripada waktu yang sepatutnya bangunan

itu runtuh. Sekiranya pembinaan diteruskan di atas permukaan tanah lembut ini, ianya

sangat berisiko tinggi tanpa usaha untuk meningkatkan kekuatan tanah itu sendiri. Oleh

sebab itu, pengubahsuaian yang betul terhadap tanah lembut amat penting untuk

membuatkan tanah lembut itu berubah menjadi lebih baik dan menpunyai sifat yang

kuat menampung beban. Pengubahsuaian yang betul boleh melayakkan tanah lembut ini

untuk digunakan dalam industri pembinaan kelak. Terdapat pelbagai cara untuk

meningkatkan kekuatan tanah tersebut. Kajian ini memfokuskan kepada penstabilan

tanah di mana tanah liat S300 distabilkan dengan pelbagai peratus kapur dan 4% serbuk

silica. Peratus kapur yang digunakan dalam kajian ini ialah 3%,5%,7% dan 9%.

Manakala peratus bagi serbuk silica adalah tetap iaitu 4%. Tujuan utama kajian ini

adalah untuk mengurus dan memantau peningkatan kekuatan ricih tanah lembut yang

distabilkan dengan pelbagai peratus kapur dan 4% serbuk silica. Peningkatan kekuatan

tanah dipantau berdasarkan peratus kapur yang berbeza dan 4% serbuk silica. Antara

ujian fizikan dan mekanikal yang terlibat dalam kajian ini adalah Had Atterberg, ujian

kebolehtelapan, ujian pemadatan tanah, ujian serakan (Hidrometer), dan ujian graviti

tentu. Setelah ujian ini dilakukan, sifat tanah liat lembut ini dibandingkan antara satu

sama lain dimana tanah liat sahaja dan tanah liat distabilkan dengan pelbagai peratus

kapur dan 4% serbuk silica. Ujian paling utama dalam kajian ini adalah ujian ricih

tanah. Tujuan utama ujian ini adalah untuk mengenalpasti kekuatan ricih tanah.

Berdasarkan kajian yang dibuat, nilai jumlah optimum kapur adalah sebanyak 5%. Ini

disebabkan,pada kadar 5% kandungan kapur, tekanan maksimum yang dicapai ialah

sebanyak 29.37 kPa, dimana kekuatan ricih tanah yang paling tinggi berbanding dengan

kadar peratus kapur yang lain. Ini menunjukkan kekuatan tanah liat lembut ini

meningkat sebanyak 14.28%. Kesimpulannya, berdasarkan kesuluruhan ujian makmal

yang dibuat, penggunaan kapur dan serbuk silca mebuktikan dapat meningkatkan

kekuatan tanah lembut. Akhir sekali, setelah semua ujian makmal siap, kesemua

persamaan korelasi dan nilai perpaduan disenaraikan dalam bentuk graf dan jadual.

viii

TABLE OF CONTENT

Page

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF FIGURES xi

LIST OF TABLE xii

LIST OF FIGURE xiii

LIST OF SYMBOL xvii

LIST OF ABBREVIATIONS xviii

CHAPTER 1 INTRODUCTION

1.1 Background of Study 1

1.2 Problem Statement 3

1.3 Objectives 5

1.4 Scope of Study 5

1.5 Significance of study 6

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 7

2.2 Soil Types 7

2.3 Soft Clay 10

2.4 Soil Stabilization 16

2.5 Chemical Stabilization 16

2.6 Lime Stabilization 18

ix

2.7 Silica Fume Stabilization 22

2.8 Engineering Properties 25

2.8.1 Soil Compaction 26

2.8.2 Plasticity Characteristics 30

2.8.3 Permeability 33

2.8.4 Compressibility 34

2.8.5 Shear Strength 35

2.8.6 Unconfined Compressive Strength 36

CHAPTER 3 METHODOLOGY

3.1 Introduction 42

3.2 Laboratory Works 44

3.3 Physical Properties 45

3.3.1 Atterberg Limit Test 45

3.3.2 Specific Gravity Test 47

3.3.3 Sieve Analysis Test 49

3.3.4 Hydrometer Test 50

3.4 Mechanical Properties 52

3.4.1 Standard Compaction Test 52

3.4.2 Permeability Test 53

3.4.3 Unconfined Compression Test 54

3.5 Sample Preparation 56

CHAPTER 4 RESULTS AND DISCUSSION

4.1 Introduction 58

4.2 Summary of kaolin and kaolin stabilized with various percentages 59

of lime and 4% silica fume

4.3 Physical Properties 61

4.3.1 Atterberg Limit Test 61

4.3.2 Specific Gravity 65

x

4.3.3 Particle Size Distribution 67

4.4 Mechanical Properties 69

4.4.1 Compaction 69

4.4.2 Permeability 74

4.4.3 Unconfined Compression Test 76

4.5 List of Correlation Equations and Cohesion Value 81

CHAPTER 5 CONCLUSION AND RECOMMENDATION

5.1 Introduction 82

5.2 Conclusion 82

5.3 Recommendation 85

REFERENCES 87

APPENDICES A-F

A Atterberg Limit Test Results 92

B Specific Gravity Test Results 97

C Hydrometer Test Results 100

D Permeability Test Results 105

E Compaction Test Results 110

F Unconfined Compression Test Results 116

xi

LIST OF TABLE

TABLE NO. TITLE PAGE

2.1 Soil types based on particle sizes (Gofar and Kassim, 2005) 9

2.2 British Soil Classification system (Gofar and Kassim, 2005) 9

2.3 General of clay characteristics ( Holtz and Kovacs, 1981) 11

2.4 Strength of Soft Ground Clay (Terzaghi and Peck , 1948) 12

2.5 Physical and chemical properties of typical white kaolin

(Eisazadeh et al., 2007)

13

2.6 Basic properties of untreated kaolin (Muhmed, 2013) 14

2.7 Suggested lime content (Ingles, 1972) 20

2.8 Chemical composition of silica fume minerals (El-Aziz et

al., 2003)

24

2.9 Test on clay soils treated with optimum amount of lime (Bell

and Tyrer, 1987)

29

2.10 Comparison index and shrinkage properties of untreated and

treated expansive soil samples with lime (Siddique, 2013)

32

2.11 Unconfined compressive strength of lime stabilized

expansive soil (Siddique, 2013)

39

3.1 Summary of Laboratory Test Program 44

3.2 Classification of soil according to permeability (Terzaghi,

1967)

54

4.1 Summary of kaolin clay properties 59

4.2 Summary of kaolin clay stabilized with (3%, 5%, 7%, 9%)

of lime and 4% silica fume

60

4.3

Summary of specific gravity value of kaolin and stabilized

kaolin

65

4.4 Particle size distribution analysis results for kaolin and

kaolin mixed with various percentages of lime and 4% silica

fume according to BS 5930:1999

69

4.5 Summary value of maximum dry density and optimum

moisture content of kaolin with stabilized kaolin

70

xii

4.6 Summary value of hydraulic conductivity based on lime

content

74

4.7 Summary value of maximum stress and axial strain 77

4.8 Correlation equation and cohesion value for all physical and

mechanical properties test

81

xiii

LIST OF FIGURE

FIGURE NO.

TITLE PAGE

2.1 Particle size distribution graph for Pekan soft clay (Zukri,

2012)

15

2.2 Soil classification based on BS 5930:1999 (Head, 1992) 15

2.3 Effect of silica fume on the dry unit weight and moisture

content (Kalkan, 2012)

25

2.4 Typical compaction curve (Rodriguez et al., 1988) 27

2.5 Moisture content versus dry density (Siddique, 2013) 28

2.6 Effect of lime on atterberg limit (Muhmed, 2013) 30

2.7 Plastic and liquid limit of kaolinite, montmorillonite, and

fine quartz with various addition of lime content (Bell,

1996)

31

2.8 Unconfined compressive strength against percentage of

lime content for 0, 7, 14 and 28 days curing period

(Farooq, 2011)

38

2.9 Unconfined compressive strength with varying

percentage of lime content (Farooq, 2011)

38

2.10 Effect of lime on unconfined compressive strength

(Siddique, 2013)

40

2.11 Consumption of lime needed to achieve optimum strength

(Muhmed, 2013)

41

3.1 Flow Chart of the Project Methodology 43

3.2 Cone penetrometer for liquid limit test 46

3.3 Soil thread of 3.2mm in diameter 46

3.4 Plasticity chart 47

3.5 Preparation for small pyknometer test 48

3.6 Small pyknometer samples in the vacuum dessicators 49

3.7 Sieve shakes analysis 50

3.8 Hydrometer test apparatus 52

xiv

3.9 Compaction test apparatus 53

3.10 Permeability test apparatus 54

3.11 Unconfined compression test apparatus 55

3.12 Kaolin, lime and silica fume before mixed together 57

3.13 180 mm height and 50 mm internal diameter steel mold 57

4.1 Effect of various lime content with (4%) silica fume on

Atterberg limits.

61

4.2 Plasticity chart (ASTM D2487) 63

4.3 Correlation graph of liquid limit with various percentages

of lime and 4% silica fume

63

4.4 Correlation graph of plastic limit with various

percentages of lime and 4% silica fume

64

4.5 Correlation graph of plasticity index with various

percentages of lime and 4% silica fume

64

4.6 Effect of stabilizer content on specific gravity 66

4.7 Correlation graph of specific gravity with various

percentages of lime and 4% silica fume

66

4.8 Particle size distribution of kaolin clay S300 68

4.9 Particle size distribution of kaolin and kaolin mixed with

various percentages of lime and 4% silica fume

68

4.10 Variation of the dry density with moisture content for

different lime percents

70

4.11 Effect of various percentage of lime with 4% silica fume

on the optimum moisture content

72

4.12 Effect of various percentage of lime with 4% silica fume

on the maximum dry unit weight

72

4.13 Correlation graph of optimum moisture with various

percentages of lime and 4% silica fume

73

4.14 Correlation graph of maximum dry unit weight with

various percentages of lime and 4% silica fume

73

xv

4.15 Effect of various percentages of lime and 4% silica fume

on the hydraulic conductivity

74

4.16 Correlation graph of various percentages of lime and 4%

silica fume on the hydraulic conductivity

76

4.17 Stress-strain relationships from unconfined compression

test

77

4.18 Effect of various percentage of lime and 4% silica fume

on the compressive strength

79

4.19 Correlation graph of various percentages of lime and 4%

silica fume on the compressive strength

79

4.20 Mode of failure of sample 80

xvi

LIST OF SYMBOLS

Gs - Specific Gravity

k - Hydraulic conductivity

kN - Kilo Newton

kPa - Kilo Pascal

Mg - Mega Gram

MN - Mega Newton

m/s - Metre per Second

mm - Milimetre

µm - Micrometre

qmax - Maximum deviator stress

qu - Undrained Shear Strength

�� - Plasticity index

�� - Liquid limit

�� - Plastic limit

w - Moisture Content

wopt - Optimum Moisture Content

�� - Dry Density

��(�) - Maximum Dry Density

ϕ - Internal Friction Angle

% - Percent

� - Cohesion value

xvii

LIST OF ABBREVIATIONS

ASSHTO American Association of State Highway and

Transportation Officials

ASTM American Society for Testing and Materials

CBR California Bearing Ratio

BA Bottom Ash

BS British Standard

BSCS British Soil Classification System

K Kaolin

L Lime

LL Liquid Limit

OL Low plasticity organic clay

PI Plastic Index

PL Plastic Limit

SF Silica fume

SL Shrinkage Limit

UCS Unconfined compressive strength

UCT Unconfined Compression Test

US United States

USCS Unified Soil Classification System

CHAPTER 1

INTRODUCTION

1.1 Background of Study

Clayey soils are usually categorized as expansive soils. Other names of these

soils are soft soils or fine-grained soils. These types of soils are known lead to critical

damage to structures resting on them. Normally in construction industries, the structures

that constructed on clay soils are tend to trigger the soil when exposed to additional load

as well as external impact. This deformation could potentially cause significant failure

to foundation and structures. Besides, the construction of roadway on the soft soils also

encountered the same problem. This is because the soils do not have enough physical

properties for construction application. It is very risky if the construction is still

continuing on these types of soils without any remediation or improvement on the soils.

As a general knowledge, the common approach when facing this difficulty is to remove

all the soils and replace it with stronger soils or material like crushed rocks. The

excessive expenses regarding the soils replacement cause the researcher to explore

another method to make the cost become more reasonable.

Nowadays, there are many methods to improve the soils. From time to time,

researchers make use of soils stabilization technique to enhance the geotechnical

characteristics of clay soil to maintain roadways, control foundation settlement, prevent

structures from collapsing, as well as avoid any kind of related failure. Various soil

stabilization techniques are suitable for stabilization involving expansive clayey soil.

These kinds of methods consist the application of chemicals, soil replacing, rewetting,

moisture control, compaction control, surcharge loading and thermal methods (Chen,

1988; Nelson and Miller, 1992; Yong and Ouhadi, 2007). Instead of using chemical

product, recycled or reused materials usually are might offer more economical options

2

for a variety application of soil stabilization. As an example we can use lime and silica

fume to improve the soil characteristics and also the performance of the soil.

Preservation with the aim of getting rid of all environmental considerations is really a

series issue (Edil & Craig, 2007). All these methods may have their advantages and

disadvantages of being ineffective and also costly. Therefore, new methods are still

being research to improve the strength properties in order to reduce the swell potential

of expansive soils.

As an example, cement was initially utilized as a stabilizing agent in the

beginning of the 20th century. It had been combined with the soils in order to create road

materials and was used in a wide range of applications worldwide. Since then, many

other materials such as lime, fly ash, silica fume, organic polymers and other mixtures

have been used as stabilizing agent. Among the stabilizing agent that have been

identified, lime and silica fume have been selected in this research because these types

of materials have good characteristics to improve its stability, increase the bearing

capacity and reduce settlement and lateral deformation of the clayey soil. Type of clay

use is Kaolin S300. As a general knowledge, kaolin is a clay mineral with the chemical

composition Al�Si�O�(OH)� (Weaver & Pollard, 1973). Kaolin has a minimal shrink

swell capacity and low cation exchange capacity. It is easy to absorb water and will

shrink as water is drawn away. This kind of clayey soil contains clay mineral that have

the possibility of swelling and shrinkage under transforming water content.

Lime provides an economical as well as powerful way of chemical

improvement. The standard utilization of lime stabilization is in the treatment of clay

subgrade to create improved road foundation without necessity for large amounts of

imported granular aggregates. In United States and Europe, lime stabilization is actually

popular regarding improving traffic ability, loading capacity of foundations of road and

embankment and also for erosion control (Perry et al., 1977). Contrary to lime

modification, lime creates long lasting improvements in soils characteristics offering

structural benefits. Other than improving roadways, lime also treat foundations and

embankment. Silica fume is very fine dust of silica from a blast furnace produce during

silicon metal production and it has historically recently been considered as a waste

product. Based on the previous study, it is indicating that silica fume help to improves

3

geotechnical properties of the fine-grained soils for example hydraulic conductivity,

swelling behavior, and unconfined compressive strength (Aiticin et al., 1984). In

addition, silica fume also have the ability to reduce the effects regarding freezing and

also thawing cycles on the strength as well as permeability within the landfill liner and

cover systems. Among the pozzolanic materials, silica fume has becomes the most

effective by-product due to its extremely energetic and higher pozzolanic property (Atis

et al., 2005).

1.2 Problem Statement

Clay present difficulty to geotechnical engineer due to its complex nature and

also contains variable materials. In the preliminary stage, the soils do not have enough

physical properties for construction purpose. This is because; marginal soils which

include soft clays, loose sand, and organic are not satisfactory materials for construction

applications. However, this type of soils are very important in geology, construction,

and also for the environmental applications because of their wide consumption as

impermeable along with containment barriers inside landfill areas and other

environmentally applications (Kayabali et al., 1997). As an example, during the site

investigation process, if the soil at any particular locality is unsuitable entirely or

partially based on the engineer requirements a fundamental decision must therefore be

generated whether to be able to remove the site materials and replace with a superior

materials or just accept as it is and design to standard sufficient to meet the constraints

by its recent quality or the last choice is to alter the properties of existing soil to become

better and meet the engineer requirement.

Nowadays, the construction on soft soil is growing because of insufficient

appropriate terrain for infrastructures as well as other developments. In this research,

study is carried out by using kaolin S300 clay mixed with lime and silica fume. One of

the well known waste industrial materials is silica fume. In western countries, it has

recently become environmentally undesirable to produce the fume in to the atmosphere

and thus it is collected (Aiticin et al., 1983). Awareness is very important related to the

harmful issue of the silica fume. Hence, we need to fully utilize the silica fume wisely

4

as a stabilization material. Although silica fume is the waste product of industrial, the

material has become the most valuable by-product among the pozzolanic materials

because of its very active and also higher pozzolanic property (Atis et al., 2005).

According to Kalkan (2009) it absolutely was observed that silica fume improved much

better the properties of clayey soil as well as make the clayey soil become more

strength. In soil stabilization, binder material is very crucial to make each of the

particles join and hold firmly. The binders is important to improve mechanical and

chemical properties of the stabilize soil (Ancade, 2007). Some examples of the binders

are lime, cement and other pozzolanic materials. In this research, lime treatment is

carried out with the clayey soil considered inadequate amount in construction as well as

recycle involving these kind of material will probably make environment become more

friendly and also financial benefits by reducing expenses (Usman et al., 2005). In

addition, lime required less time to react with all the materials and also improved the

chemical properties of soil in a more comprehensive technique (Osula, 1996). By

utilizing waste product within soil stabilization purpose, retains these types of products

from getting trashed directly into landfills. Therefore, conserving method is already

using up landfill area.

Chemical stabilization of clay soil has been proved to be effective in increasing

its strength and stiffness. Lime and silica fume provides one such means. As an extra

advantage, make use of waste material in soil stabilization purpose, keeps these material

from being dumped into landfills, thereby saving already the use of landfill space. For a

successful stabilization, laboratory test followed up by field test is required in order to

determine the engineering properties of soil. Therefore, in order to prevent the

problems, it is important for engineers to stabilize the existing soil before starting the

construction activities. By simply stabilizing the soil, it is expected that soil could be

more suitable for any type of construction such as road or building construction. Thus, a

suitable method to make sure strength of kaolin is improved is by mixing it with lime

and silica fume as a stabilizer.

5

1.3 Objectives of Study

The objectives of this research are as follows:

I) To determine the physical characteristics of kaolin and kaolin mixed various

percentage of lime and 4% silica fume

II) To determine the undrained shear strength of kaolin and kaolin mixed with

various percentage of lime and 4% silica fume

III) To correlate the undrained shear strength of kaolin mixed with various

percentage of lime and 4% silica fume.

1.4 Scope of Study

All testing was conducted in Geotechnical Engineering Laboratory, Universiti

Malaysia Pahang (UMP). This research is mainly focused on stabilizing of kaolin clay

(S300) using selected agents that were lime and silica fume. Laboratory testing methods

will be conducted to test the strength, behavior and performance of stabilized soils.

The physical and mechanical properties of kaolin were determined from the following

laboratory test:

I) Liquid Limit And Plastic Limit Test

II) Specific Gravity Test

III) Standard Compaction Test

IV) Falling Head Permeability Test

V) Hydrometer Test

The effective strength parameter of kaolin only and stabilized kaolin was determined

from Unconfined Compression Test (UCT) with the following step:

I) Every batch of sample was produced by using compaction method by make sure that

the size of the samples is same as well as exact size.

II) Diameter and height of each sample was 50mm and 100mm respectively.

III) After all the samples is well prepared, the UCT test is run and the data was

analyzed.

6

1.5 Significance of Study

This research will be carried out to determine how far the performance of kaolin

mixed with lime and silica fume. The work presented in this research is a contribution

to the application of chemical stabilization techniques, for different concentration of

lime and silica fume for kaolin clay. Therefore, this research provides insight into which

stabilizers are most effective for stabilizing kaolin clay. This report can be used as a

guide to select an appropriate stabilizer type and the amount of stabilizer based on the

soil properties and the desired strength. All the problems regarding silica fume harmful

can be solved by utilizing it as a stabilizing agent mixed with lime and kaolin.

Therefore, the bearing capacity of clayey soil is increased and settlement of structure

foundation is reduced. Hence, it increased the availability of marginal sites for small

expenses and long term construction.

The main objective in this research is to evaluate the engineering properties of

kaolin clay which is stabilized with different admixtures such as lime and silica fume.

The improvement of soil is observed based on different percentage of lime and silica

fume mixed with kaolin compared with kaolin only. A series of laboratory tests were

carried out to prove that kaolin become more improved when mixed with stabilizing

agents for soil stabilization technique. After the completion of this research, the

problem related to strength of kaolin was solved with one solution. The usage of lime

and silica fume as stabilizing agents was able to increase bearing capacity and shear

strength of the clayey soil as well as reduced the waste of industrial waste of silica fume

which currently disposed in large quantity into landfill. Apart from that, it can be

considered as economic and environmental friendly since the silica fume is a waste

generated during silicon metal production

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

In this literature review, there will be further explanation about the components of

this study for any related issue and the definition in-depth. The sources are from various

sources such as books, journals website and articles. This chapter will provide a clear

understanding of the research objective, problem statement, and the significant of the study

2.2 SOIL TYPES

With regard to engineering purpose, soil is defined as the uncemented aggregate of

mineral grains and also decayed organic and natural matter (solid particles) with liquid as

well as gas inside the empty spaces between the solid particles. Soil may be split up into

three very wide categories; cohesive, non-cohesive, and organic soil. As a general

knowledge, organic soil is the organic and natural matter element of soil comprising of

plant and animal residues at numerous phases of decomposition, ingredients synthesized by

soil organisms, and cells and tissues of soil organisms (Groenigen et al., 2010). Non-

cohesive soil has strength on their owned. Any free running kind of soil for example sand

or gravel whose strength is depend on friction between particles. On the other hand, if

sandy or gravely soil is geologically confined, they can produce strength properties but the

strength is depending on the confinement not the materials itself.

8

Cohesive soil is (mostly clay, but also silty clay, and clay-sand mixtures with clay

being main element). Most of these soils usually contain adequate amount of clay in order

to success bind the actual mass together. In addition, they have the ability to be molded or

shaped. This property is called ‘plasticity’. This type of soil possesses inner strength, can be

compacted and compressed and usually suitable for foundation materials under optimum

moisture conditions. According to Coduto (1999) clayey soil cannot easily be segregated by

sieve analysis into size groups because no particle sieve made with small opening instead

of the particle size may be determined by observing settling velocities of the particles in a

water mixture.

Clayey soil generally has low shear strength and will become more easily to lose

shear strength during wetting or any other physical disturbance. Plastic and compressible

are their properties. The soil condition will shrink when dried and tend to get expand when

wetted. When a constant load is applied to the cohesive soil, it can suddenly slip (deform

plastically) when the shear strength reach it limit and will cause landslides to occur. In that

condition, large lateral load is produce and the soil have low permeability (Coduto, 1999).

The particle size in soil is varying from 100mm to less than 0.001mm. Table 2.1 below

describes details about the size of particles between limits and also Table 2.2 that describe

about the size of soils according to British Soil Classification System (BSCS).

9

Table 2.1: Soil types based on particle sizes

Particle sizes (mm)

Soil Types British Standard

(BS)

ASTM

D422/ D635 USCS

AASHTO

Boulders > 200 > 300 > 300 > 75

Cobbles 60 – 200 75 – 300 75 – 300

Gravel 2 – 60 4.75 – 75 4.75 – 75 20 – 75

Sand 0.063 – 2 0.075 – 4.75 0.075 – 4.75 0.075 – 2

Silt 0.002 – 0.063 0.005–0.075 0.005 – 0.075 0.005 – 0.075

Clay < 0.002 < 0.005 < 0.005 0.001 – 0.005

Colloids < 0.001

Source: Gofar and Kassim (2005)

Table 2.2: British Soil Classification system

Very coarse

soils

BOULDERS > 200 mm

COBBLES 60 – 200 mm

Coarse soils

G

GRAVEL

Coarse 20 – 60 mm

Medium 6 – 20 mm

Fine 2 – 6 mm

S

SAND

Coarse 0.6 – 2.0 mm

Medium 0.2 – 0.6 mm

Fine 0.06 – 0.2 mm

Fine soils

M

SILT

Coarse 0.02 – 0.06 mm

Medium 0.006 – 0.02 mm

Fine 0.002 – 0.006

C

CLAY < 0.002

10

Source: Gofar and Kasim (2005)

2.3 SOFT CLAY

From the past until now, many construction industries were facing with challenging

soft clay soil construction. This is because of the soil itself engineering properties that are

shape and size, type and strength of structural bonds, high compressibility, low shear

strength and low permeability of soil (Das, 2006). All of these characteristics are dangerous

because it leads to excessive settlement problem, and reduce bearing capacity. To construct

on this type of soil, either specially design foundation or pre treatment of soil is compulsory

with regard to low cost construction for develop houses and road infrastructure (Chan,

2006). Therefore, it is not practical to remove and replace the soft clay soil with another

type of string soil because the process is very expensive and take a lot of time.

The treatment required the knowledge of physical properties of soft clay and their

effect on the usage of soft clay in the field. According to Unified Soil Classification System

(USCS), clay are categorized as fine grained soils with more than 50% by weight passing

No. 200 US standard sieve (0.075mm. This dimension has larger surface areas compared to

coarse grained soils. Generally, clayey soil is referred to clay mineral made up of a mass

fine mineral particles as well as linked with certain quantity of water, it will revealed

plasticity characteristics. There are three major minerals consisted in clay minerals. There

are kaolinite, illite, and montmorillonite. Table 2.3 below describes general characteristics

of clay minerals.

11

Table 2.3: General of clay characteristics

Mineral Kaolinite Illite Montmorillonite

Typical thickness (nm) 50 – 2000 30 3

Typical diameter (nm) 300 – 4000 10000 100 - 1000

Specific surface (m�/g) 10 – 30 50 – 100 200 - 800

Cation exchange capacity

(meq/100g)

3 25 100

Activity (PL/ %clay) 0.3 - 0.5 0.5 - 1.3 1.5 - 7

Swell potential low medium high

Source: Holtz and Kovacs (1981)

Soft clay soil can be yellow, red, brown, grey or various combinations of those

colors (Steele, 1976). By testing most of the fined grain soil, they are known to be derived

from in-situ weathering factor that is metamorphic rocks and igneous rocks and limestone

continues to be non dispersive (Sherrad and Decker, 1977). Most of the soft clay particles

have particles size lower than 2µm and the particles also are easily breakdown to this

dimension (Liu and Evett, 2005). Table 2.4 below shows the soft clay classification

according to their compressive strength. Based on Kempfert and Gebreselassie (2006), soft

soil can be clay or silt depends on the geological young and also under a well balanced

condition because of its own weight has not yet gone through significant secondary

consolidation simply by its formation. However, there are possibilities in large deformation

although the soft clay soil is able to carry its own overburden weight and any other

imposed additional load.

According to British Soil Classification System (BSCS), clay soils composed of

35% to 100% fines in which the clay particles predominate to produce plasticity, cohesion

and low permeability.