the potential of cement stabilization in soft soil …

THE POTENTIAL OF CEMENT STABILIZATION IN SOFT SOIL

NUR DIYANA BINTI NORDIN

AA08009

A thesis submitted in fulfillment of the requirements for the award of

Bachelor of Civil Engineering

Faculty of Civil Engineering & Earth Resources

Universiti Malaysia Pahang

DECEMBER 2010

ABSTRACT

Soft soils often cause difficulties in construction, operation with their low strength

and low stiffness nature. However, the engineering properties of these soils can be

enhanced by soil stabilization. This research was carried out to study the potential of

cement (OPC) stabilization in soft soil around the area of Pekan, Pahang. The

objectives of this research are firstly to determine engineering properties of soft soil.

The soil was classified as clay with very high plasticity (CV), having liquid limit,

plastic limit., plastic index and shrinkage limit of 72.0%, 31.36%, 40.64%, and 7.86%

respectively, specific gravity was 2.51 and maximum &y unit weight and optimum moisture content of 14.45kN/m3 and 20.0% respectively. Secondly, to compare the

strength and characteristic of soft soil before and after treating with different range of

cement concentration, ranging from 2% to 12% of weight of soil. Compaction test

was applied to determine the maximum dry unit weight and the optimum moisture

content of the soils. From this testing, the maximum dry unit weight was obtained for

sample with 10% cement added. By compaction test with mixing water content of 401/o the samples for triaxial test (Unconsolidated Undrained Test) were prepared

and then cured in water for 0, 1,7 and 28 days respectively to allow for investigation

of the curing effect. The result showed the shear stress is increasing proportional to

the cement ratio within curing period. The maximum shear stress was observed for

samples with 10% cement added. Oedometer test was carried out to examine the

relationship between void ratio and applied pressure to the soil sample. From this

test, it showed that 4% and 6% of cement content in the soil were effective in

decreasing the settlement of the originally weak soil or another word, increasing the

applied pressure to the soil samples would decreases the void ratio of the soil

samples. For overall, 10% of cement content shows the effective amount cement added in soft soil stabilization and the objective of this research was achieved.

V

ABSTEAK

Tanah Iernbut sering menyebabkan kesulitan dalam operasi pembinaan dengan

kekuatan dan sifat kekerasan yang rendah. Namun sifat teknikal dari tanah dapat

dipertingkatkan dengan penstabilan tanah. Penyelidikan mi dilakukan untuk

rnengkaji potensi simen (OPC) menstabilkan tanah lembut sekitar kawasan Pekan,

Pahang.. Tujuan dari penyelidikan mi adalah pertama untuk menentukan sifat

kejuruteraan tanah lembut. Tanah dikiasifikasikan sebagai tanah hat dengan

keplastikan yang sangat tinggi (CV), mempunyai had cecair, had plastik, indek

kepiastikan dan had susut masing-masing adalah 72,00/o, 31,36%, 4064%, dan

7.86%, nilai graviti tentu adalah 2.51 dan berat unit kening yang maksimuin dan kadar air optimum, masing-masing adaiah 14.45kN1rn3 and 20.0%. Kedua adalali

untuk membandingkan kekuatan dan cini-ciri tanah iembut sebelum dan selepas

sampel tanah dicampurkan dengan kandungan simen yang berbeza bennula dan 2%

hingga 12% danipada berat tanah. Ujian pemadatan digunakan untuk menentukan

berat unit kering yang maksimum dan kadar air optimum dari tanah. Daripada ujan

mi, berat unit kering yang rnaksimum diperolehi danipath sampel yang ditaznbah

dengan 100/4 siinen. Danipada ujian pemadatan dengan kadar air pencampuran 40%, sampel untuk tjian tiga paksi (ujian tak terkukuh tak tersahir) disediakan dan

kernudiannya diawet dalam air selarna 0,1,7 dan 28 had untuk mernbolehkan kajian

kesan daripada pengaruh awetan. Keputusan menunjukkan tegangan ricih meningkat

setanding dengan nisbah simen dalam tempoh awetan. Tegangan ricih yang

maksimum diperolehi untük sampel dengan 10% kandungan simen. IJJ ian oedometer

dilakukan untük menguji hulungan antara nisbah lompang dan tekanan yang

dikenakan keatas sampel tanah. Ujian mi menunjukkan bahawa 4% dan 6% adalah

kandungan simen dalam tanah yang efektif dalam pengurangan pemendapan path

tanah yang awalnya lemah atau dalam erti kata lain, meningkatkan tekanan yang

dikenakan keatas sampel tanah akan mengurangkan nisbah lompang sampel tanah.

Untuk keseluruhan, 10% kandungan simen rnenunjukkan kadar yang paling efektif

dalam penstabilan tanah lembut dan objektifpenyehidikan mi tercapai.

vi

TABLE OF CONTENTS

CHAFFER

TITLE PAGE

TITLE PAGE i

DECLARATION ii

DEDICATION iii

ACKNOWLEGDMENT iv

ABSTRACT v

A13STRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF ABBREVIATIONS xv

LIST OF SYMBOLS xvi

LIST OF APPENDICES xvii

1 INTRODUCTION

1.1 Background of Research 1

1.2 Problem Statement 3

1.3 Research Objectives 6

1.4 Scope of Study 6

1.5 Significant of Study 7

VI'

VIII

2

LiTERATURE REVIEW

2.1 Soft soil 9 2. 1.1 Properties 12

2.2 Soil stabilization 15 2.2.1 Mechanical stabilization 16

2.2.1.1 Soil replacement method 17 2.2.1.2 Compaction 17 2.2.1.3 Vibration by Vibmflôtation 18 2.2.1.4 Dewatering by vertical drain 19

2.2.2 Additive stabilization 21 2.2.2.1 Cement 22

2.2.2.2 Lime 23

2.2.2.3 Bitumen 24

2.2.2.4 Selection of stabilizer 25 2.3 Stabilization with Portland cement. 28

2.3.1 Types of Portland cement 30 2.4 Principles of laboratory testing 30

2.4.1 Particle Size Distribution (Mechanical Analysis) 31

2.4.1.1 Sieve Analysis 32

2.4.1.2 Laser Particle Size Analyzer 33 2.4.2 Atterberg Limit 33 2.4.3 Determination of specific gravity 34 2.4.4 Standard Proctor Test 35 2.4.5 Triaxial Test (Unconfined Undrained Test) 35

2.4.6 Oedometer Test 36

3 METHODOLOGY

3.1 Introduction 37

3.2 Soil preparation 40

3.3 Soil classification test 41

3.3.1 Particle Size Distribution (Mechanical Analysis)

3:3.1.1 Sieve Analysis

3.11.2 Laser Particle Size Analyzer

3.3.2 Atterbe rg Limits

3.3.2.1 Liquid Limit (LL)

3.12.2 Plastic Limit (PL)

33.2.3 Plasticity Index (P1)

3.3.2.4 Shrinkage Limit (SL)

3.3.3 DcterniLnation of Specific Gravity

3.4 Standard Proctor Test

3.5 Triaxial Test (Unconsolidated Undrained Test)

3.6 Oedometer Test

4

RESULT AND ANALYSIS

4.1 Introduction

4.2 Particle Size Distribution

4.2.1 Dry Sieving

4.2.2 Laser Particle Size Analyzer

4.3 Soil classification test

4.3.1 Atterberg Limits

4.3.2 Determination of Specific Gravity

4.4 Standard Proctor Test

4.5 Triaxiai Test (Unconsolidated Undrained Test)

4.6 Oedometer Test

5 CONCLUSION AND RECOMMENDATIONS

5.1 Introduction 78 5.2 Conclusion 79

5.3 Recommendation 80

ix

42

42

44

45

46

47

48

49

so

Si

53

56

58

59

59

62

64

64

66

67

69

75

REFERENCES

APPENDICES A - G 85

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Typical properties of soil (Reuben, 2003) 13 2.2 Permeability ranges for various soils (Reuben, 2003) 13 2.3 Guide for selecting a stabilizing additive (Das, 2007) 27 2.4 Cement requirement by Volume for Effective 29

Stabilization of Various Soils a([) 2007)

25 Typical Compressive strengths of Soils and Soil-Cement 29

Mixtures (Das, 2007)

3.1 List of tests and reference 38 3.2 U.S. standard sieve sizes 43 4.1 Compaction Test Result 68

XI

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 The location map ofPekan,Pahang 5

2.1 Peninsular Malaysia soil coverage in terms of Great ii

Soil Groups (iegHCM-PM)

2.2 Vibroflotation method (Reuban, 2003) 19

2.3 Preloading with vertical drains (Chu et al., 2004) 20

2.4 Appropriate Additive Stabilization (After Dept. of 22

Army, 1983)

2.5 Gradation triangles for aid in selecting a commercial 26

stabilizing agent .(Das, 2007)

2.6 The classification of laboratory tests (Ling, 2005) 31

2.7 Typical compaction curve (Das, 2007) 32

2.8 Moisture content versus volume relation 34

(Liu & Evett, 2003)

3.1 Flow of activities of research 31

3.2 Percussion drilling sets 40

3.3 Percussion gauge 40

3.4 Soil sample in Percussion gouges 41

3.5 Mechanical shaker for dry sieving 44

3.6 CILAS 1180 Liquid instrument 45

3.7 Cone Penetrorneter apparatus 46

3.8 Plasticity chart 48

3.9 Density bottle method apparatus 50

xli

.x111

3.10 Density bottle in vacuum desiccators 51

3.11 Standard Proctor Test apparatus .52

3.12 Adiagrarn of the tiiaxial test equipment 53

3.13 Triaxial test equipment 54

3.1.4 Triaxial test apparatus 54

3.15 The, chamber of the triaxial cell, filled with water 55

3.16 'Odoemeter test machine 57

4.1 Particle Size Distribution Curve for Sample 1 60

4.2 1 article Size Distribution Curve for Sample 2 60

4.3 Particle Size Distribution Curve for Sample 3 61

4.4 Particle Size Distribution Curve (Average) 61

4.5 CILAS 1180 Liquid instrument 62

4.6 Distribution Curve (Laser particle size analyzer) 63

4.7 Graph of cone penetration versus moisture content 64

4.8 Plasticity 'Chart 65

4.9 The sample in density bottle 66

4.10 Compaction Curve 67

4.11 Curing Process 69

4.12 Shear stress with cement content 70

4.13 Stress-strain relationship for specimens with 2% of 71

cement. & curing time


cement & curing time



4.16 Stress-strain relationship for specimens with 8 1/6 of 72

cement. & curing time





4.19 Mode of failure for triaxial sample 74

4.20 Total stress Mohr's circles and failure envelope (4 0) 75

xiv

4.21 Relationship between Void ratio and applied pressure 76

for specimen with different concentration of cement

content

LIST OF ABBREVIATIONS

OPC - Ordinary Portland Cement

ASTM - American Society for Testing of Materials

BS - British Standard

LL - Liquid Limit

PL - Plastic Limit

SL - Shrinkage Limit

P1 - Plasticity Index

CD - Consolidated-drained

CU - Consolidated-undrained

UU - Unconsolidated-undrained

xv

LIST OF SYMBOLS

g - Gram

mm - Millimeter

m - Meter

cm - Centimeter

% - Percent

kPa - Kilo pascal

Gs - Specific gravity

L0 - Initial length

LD - Oven-dried length

V - Volume

M - Mass

W - Weight

P Density

Ywet - Wet unit weight

Yd - Dry unit weight

C - Undrained shear strength (mohr's circle)

Cu - Shear strength

e - Void ratio

- Strain

G3 - Total and effective confining stress

a1 - Total and effective axial stress at failure

4) - Angle of friction

xvi

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Particle Size Distribution (Dry sieving) 85

B Particle Size Distribution (Laser particle size analyzer) 88

C Atterberg Limit

97

D Determination of Specific Gravity 99

E Standard Proctor Test 101

F Triaxial Test (Unconsolidated Undrained Test) 122

G One-Dimensional Test 139

iNTRODUCTION

1.1 Background of Research

The emergence of development in construction industry has minimized the

preferred site of geotechnical quality for construction although these sites are known

to reduce technical problems and thus the cost associated with their construction. By

that, socio-economic and political considerations have forced the use of sites of

lower quality and in particular, the site covered by compressible soils.

In developed country such as Malaysia, the chances to have good quality

construction sites become rarer and it is necessary to choose sites that include

compressible soils, especially for industrial structures and transportation projects.

Therefore, the tasks to do constructions on these problematic soils have become a

challenge for geotechnical engineers all over the world. The ground or soil condition

is one of the important factors in foundation design. Before starting to design a

foundation, a civil engineer must first obtain the required soil, information from soil

investigation carried out at the proposed site. Therefore, a civil engineer must have

an adequate knowledge on the properties of soil and the soil testing.

Soils with characteristics of low strength and compressible exist all over the

world. One of the most significant problems arises because of its characteristics that

are difficulties in supporting loads on such foundation. The problem arises with low

PA

strength is that it leads to difficulties in guaranteeing the stability of the structure on

this type of soil.

Therefore, the stabilization of soil is important to be done in the construction.

The main purposes of soil stabilization are to modify the soil, expedite construction,

and improve the strength and durability of the soil. Besides that, soil stabilization

also can be defined as the modification or improvement of the characteristics of soil

in order to enhance the engineering performance of the soil. For example, improve

the density of soil, mixing the soil with additives to change the chemical and physical

properties such as stiffness, compressibility, permeability, workability, lower the

ground water level, and eliminate weak soil.

The term modification implies a minor change in the properties of a soil,

while stabilization means that the engineering properties of the soil have been

changed enough to allow field construction to take place. There are two primary

methods of soil stabilization used today, mechanical and additives. The method of

soil stabilization is determined by the amount of stabilizing required and the

conditions encountered on the project. An accurate soil description and classification

is essential to the selection of the correct materials and procedures. The most

common improvements achieved through stabilization include better soil gradation,

reduction of plasticity index or swelling potential, and increases in durability and

strength.

Mechanical stabilization is the process of altering soil properties by changing

the gradation through mixing with other soils, densifying the soils using compaction

efforts, or undercutting the existing soils and replacing them with granular material.

The examples of mechanical method are soil replacement, vibroflotation, compaction

and others.

In additive method, stabilization of soils to improve strength and durability

properties often relies on cement, lime, fly ash, and asphalt emulsion. These

materials are inexpensive, relatively easy to apply, and provide benefits to many

different soil types. However, there are varieties of non-traditional soil

3

stabilization/modification additives available from the commercial sector such as

polymer emulsions, acids, lignin derivatives, enzymes, tree resin emulsions, and

silicates. These additives may be in liquid or solid form and are often touted to be

applicable for most soils. Previous research studies in this area have demonstrated

that many soil additives have little to no benefit for silt and sandy soil types (Santoni

et. al, 1787).

1.2 Problem Statement

Malaysia is a developing country located in South-East Asia. The demands

for buildings, for commercial or residential use are high especially in Kuala Lumpur,

the capital city of Malaysia. A building is designed to support the load applied to it

safely. The ability of building to sustain the applied loads depends on the soil below

the foundation of the building. The superstructure loads will be transferred to the

underlying soil. Without a proper design and earthwork construction, problem such

as cracking, settlement of building may occur and even to the extent, the whole

building may collapse within its design life. Therefore, a proper earthwork required

to maintain the safeness of a building.

Nowadays, many construction have face the problem of soil where the soil

cannot reach the required specification such as bearing capacity of soft soil too weak

to support superstructure above it. The existing soil at a construction site may not

always be totally suitable for supporting structures such as buildings, bridges,

highways, and dams. Due to that, the understanding and knowledge of engineering

characteristics of soft soil are critical and should be understand by people related in

this field. The selection of construction method on this formation is restricted by

cost, duration of completion, and benefits. in this study, the type of soil will be

focused on soft soil.

4

Soft soil is chosen as a sample in this study because of their low strength and

high compressibility. Usually, due to sedimentary process on different environments,

both physical and engineering properties (namely void ratio, water content, grain size

distribution, compressibility, permeability, and strength) show a significant variation.

Further, they exhibit high compressibility (including an important secondary

consolidation), reduced strength, low Permeability and compactness, and

consequently low quality for construction.

The problem of settlement is significant when dealing with structure such as

roads, housing and embankment constructions on soft soil. Due to the characteristic

of soft soil, the structure may settle excessively both due to high compressibility and

low shear strength. The settlement may take a long time depending on the ability of

the soil to dissipate the excess prop induced by the construction. Structures built on

soft soil are subject to settlement and some settlement is often inevitable, depending

on the circumstances, and tolerable. For example, small uniform settlement of a

building throughout the floor area might be tolerable, whereas non-uniform

settlement of the same building might not be

Clay soils can be classified as a soft soil. Some clay soils undergo slow

volume changes that occur independently of loading and are attributable to swelling

or shrinkage. These volume changes can give rise to ground movements that can also

cause damage to structures. Low rise buildings are particularly vulnerable to such

ground movements since they generally do not have sufficient weight or strength to resist.

In certain cases, the soft soil failed to support the foundation of the structure.

In this case, the softer layers are found under the intermediate layers. The presence of intermediate hard layers makes it difficult to penetrate the soil using driven or

jacking piles. It may results in the piles being falsely terminated on top of the intermediate layer. Consequently, the high building loads are transferred to the softer

layers which underlain the intermediate hard layers. This wills leads to building settlement as the loads are not properly transferred to the actual founding level.

5

This study was conducted in Pekan, Pahang. The soft soil sample was taken

near to the river mouth of Sungai Pahang. Figure 1.1 shows the location map of

pekan, Pahang.

KELANTAN

-

!4L TERENG'ANU / Q

t'U.. •'O 'a 7 . • PERAK PAHANG

.

i-fth I L.' C'-.i,,rC "- lCHr,

I I •

•1%h 4SELANGOP

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Loft U-9

sh

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I 3 - C

' • i TqiP j It. J.l.

,7'•_,•• Piu'M

• - i " •. ItI1 ct F*&LIIW A.. ..

NEGERI T •7i SEME3tLAN -*'Vjk^ Koba. ^^-Wb A-W

/11

I IfrI..

JOl-IOR -,

Figure 1.1: The location map of Pekan, Pahang

1.3 Research Objectives

The objectives of the project are:

1. To determine engineering properties of soft soil.

2. To compare the strength and characteristic of soft soil before and after

treating with different concentration of cement and curing periods.

3. To determine the effectiveness of cement in soft soil.

1.4 Scope of Study

The term of soft soils had been used in this study to describe soils that have a

high moisture content, approaching that of the liquid limit and have a high

sensitivity. Soil samples from various locations in Pekan, Pahang were collected.

Undisturbed and disturbed soil sample was taken and brought to the laboratory for

classified and to be investigated for use in soil cement. The soil samples were chosen

to represent plasticity index is less than about 25 and clay fraction (passing No. 200

sieve) are less than about 40 percent.

Ordinary Portland Cement (OPC) was used in this research. Portland cement

had proven to be a very good method of base stabilization by decrease the liquid

limit and increase the plasticity index and workability of soft soil.

For soils classification, soils included size of particle, specific gravity, and

water content, In soil classification tests, there are three laboratory testing were

carried out that are Particle size distribution test, Atterberg limits test, and Specific

gravity test. Each testing was conducted with three samples of soil to get the average

results.

7

The main testing Was carried out to compare the strength and characteristic of

soft soil before and after treating with different concentration of cement. The testing

were Standard Proctor test, Triaxial test (Unconsolidated Undrained test), and

Oedometer test. There were seven different ratios (00/o, 2%, 4%, 6%, 8%, 10%, and

12%) of cement content were mixed -with the soft soil to make soil samples. Cement

ratio is ratio of the weight of cement to the weight of soil sample.

Standard proctor test was applied to determine the maximum dry unit weight

and the optimum moisture content of the soils. Triaxial Test was conducted to

determine shear strength parameters and to allow for investigation of the curing

effect. Triaxial specimens were about in diameter and 76mm long was used

and the testing was tested fteozuriing period of 0, 1,7 and 28 days. Lastly, odometer

test was conducted to determine the consolidation characteristics of soil, for low

permeability.

1.5 Significant of Study

Many studies and researches had been carried out Demonstrating cement

stabilized soil has a significant enhancement in strength and other soil engineering

properties. With this research, tests are carried to investigate whether the sets of

tested cement stabilized has enough strength to withstand the increasing load. it

provides a reference for the behavior of compressive strength on cement stabilized

soft soil under different amount of cement contents.

Soil stabilization with cement has been successfully applied in engineering

Construction. Applications of this method have recently been further expanded. The

more Common uses today are for stream bank protection, grade control (drop)

structures, and pond liners. Soil cement has been proven in all of these uses to be cost effective, aesthetically pleasing, performance and time tested. Other uses for soil

cement are retaining walls, streets, shoulders, airports, parking and storage areas.

8

As the soil cement is placed and compacted, the cement hydrates and the mix

becomes a structural slab-like material. After construction and curing, soil cement is

hardly affected by water or the freeze thaw cycle, therefore does not pump under

construction traffic or rut during spring thaws, and can bridge over soft sub grade.

Treatment of soils offers technical, economic, ecological and environmental

advantages. For technical advantage, treatment with cement allows production and

use of homogeneous, long-lasting and stable materials with mechanical

characteristics. In addition, these materials are characterised by great stiffness and

excellent fatigue strength. They show good performance in hot weather, with no

deformation or rutting, and good performance on exposure to freeze-thaw cycles due

to the stiffness of the material.

For economic advantage, field recycling is a significant savings factor as this

reduces to a minimum stripping cuts, landfill, provision of aggregates and thus the

cost of their transport. The absence of transport of aggregates and of cuts to the

landfill contributes to preserving the road network in the vicinity of the building site.

CHAPTER 2

LITERATURE REVIEW

2.1 Soft soil

Soil is a natural body consisting of layers (soil horizons) of mineral

constituents of variable thicknesses, which differ from the parent materials in their

morphological, physical, chemical, and mineralogical characteristics

(Birkeland, 1999).

Soft soils can be considered as near-normally consolidated clays, clayey silts

and peat The special features of these materials are their high degree of

compressibility. But in the same time soft soil has a high sensitivity and low strength

compared to another types of soil and the most important problem related to building

on soft soil is settlement which is relatively large and takes long time to complete.

Usually, due to sedimentary process on different environments, both physical

and engineering properties such as void ratio, water content, grain size distribution, compressibility, permeability and strength are show a significant variation. Further,

they exhibit high compressibility (including an important secondary consolidation),

reduced strength, low permeability and compactness, and consequently low quality for construction.

10

Due to the rapid increase in population and associated development activities

taking place, especially in the congested coastal areas, construction activities have

become concentrated UI low-lying marshy areas, which are comprised of highly

compressible weak organic and peaty soils of varying thickness (Indraratna et al.,

1992). The entire coastal belt is dotted with very soft clays up to significant depths.

These soft clay deposits have very low bearing capacity and excessive settlement

characteristics, affecting major infrastructure including buildings, roads, and rail

tracks (Johnson, 1970). Figure 2.1 shows the Peninsular Malaysia soil coverage in

terms of Great Soil Groups

the potential of cement stabilization in soft soil …

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