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STRENGTH OF SOFT CLAY REINFORCED WITH GROUP CRUSHED

POLYPROPYLENE (PP) COLUMNS

NURAINI BINTI YUSUF

Thesis submitted in fulfilment of the requirements for the award of the degree of Bachelor of

Civil Engineering

Faculty of Civil Engineering

UNIVERSITY MALAYSIA PAHANG

JUNE 2015

vi

ABSTRACT

The use of granular columns as soil reinforcement technique has proved useful in

problems of foundation stability and settlement, as well as improving soft clay for

foundation construction. The purpose of this study is to investigate the enhancement of

shear strength of soft kaolin clay when it is reinforced with group crushed polypropylene

(PP) columns. Since PP is a waste material, the cost of soil improvement can be reduced

which currently was disposed totally in large quantity into landfill. In order to proceed the

study, physical and mechanical properties of materials used that are kaolin (soil sample)

and PP (reinforcing columns) must be identify first. Then, consolidated kaolin as soft clay

was reinforced with group crushed PP columns, and subsequently tested under Unconfined

Compression Test (UCT). A total of 7 batches of kaolin sample including control sample

had been tested to identify the shear strength. Each batches involved of four samples to find

the average value of maximum stress. The variables used for the columns installation were

the column height that are 60 mm, 80 mm and 100 mm, where the column penetrating ratio

are 0.6, 0.8 and 1.0 respectively. In addition, different values of columns diameter had been

used that are 6 mm and 10 mm for every different height of columns. A total of 28

unconfined compression tests had been conducted on kaolin samples. The kaolin samples

had the dimensions of 50 mm in diameter and 100 mm in height. For the group PP

reinforcement, shear strength increased about 2.13%, 13.51% and 12.84% for 1.44% area

replacement ratio and 6.85%, 14.26% and 13.79% for 4% area replacement ratio at sample

penetration ratio 0.6, 0.8, 1.0 respectively. In the other hand, the relationship of the

increment of shear strength with the various column penetration ratio show different

pattern. The shear strength of both area replacement ratio increases constantly as the

column penetrating ratio increased, but after it reach 80mm height of column, the shear

strength decrease slightly and this support the ‘critical column length’ idea. It can be

concluded that the shear strength parameters were affected by the diameter and the height

of the columns and the presence of PP column greatly improve the shear strength.

vii

ABSTRAK

Penggunaan tiang granular sebagai teknik pengukuhan tanah telah terbukti

berguna dalam masalah kestabilan asas dan mendapan, serta memperbaiki tanah liat lembut

untuk pembinaan asas. Tujuan kajian ini adalah untuk menyiasat peningkatan kekuatan

ricih tanah liat kaolin lembut apabila ia diperkuatkan dengan tiang berkumpulan

polipropilena (PP) hancur. Memandangkan PP adalah bahan buangan, kos pembaikan tanah

boleh dikurangkan yang kini telah dilupuskan sama sekali dalam kuantiti yang besar ke

tapak pelupusan. Untuk meneruskan kajian ini, sifat-sifat fizikal dan mekanikal bahan-

bahan yang digunakan iaitu kaolin (sampel tanah) dan PP (tiang pengukuhan) mesti dikenal

pasti terlebih dahulu. Kemudian, kaolin yang disatukan sebagai tanah liat lembut

diperkukuh dengan tiang berkumpulan PP hancur, dan kemudiannya diuji di bawah Ujian

Mampatan Tak Terkurung (UCT). Sebanyak 7 kumpulan sampel kaolin termasuk sampel

kawalan telah diuji untuk mengenal pasti kekuatan ricih. Setiap kumpulan mempunyai

empat sampel untuk mencari nilai purata tekanan maksimum. Pemboleh ubah yang

digunakan untuk pemasangan tiang tersebut ialah ketinggian tiang iaitu 60 mm, 80 mm dan

100 mm, di mana nisbah ruang menembusi adalah 0.6, 0.8 dan 1.0. Di samping itu, nilai-

nilai garis pusat tiang yang berbeza telah digunakan iaitu 6 mm dan 10 mm untuk setiap

ketinggian tiang yang berbeza. Sebanyak 28 ujian mampatan tak terkurung telah dijalankan

ke atas sampel kaolin. Sampel kaolin mempunyai dimensi garis pusat 50 mm dan

ketinggian 100 mm. Bagi kumpulan PP tetulang, kekuatan ricih meningkat kira-kira 2.13%,

13.51% dan 12.84% untuk nisbah penggantian kawasan 1.44% dan 6.85%, 14.26% dan

13.79% bagi nisbah penggantian kawasan 4% pada nisbah penembusan sampel 0.6, 0.8,

1.0. Di sisi lain, hubungan antara kenaikan kekuatan ricih dengan pelbagai nisbah

penembusan ruangan mempunyai corak yang berbeza. Kekuatan ricih kedua-dua nisbah

penggantian kawasan sentiasa meningkat apabila nisbah ruang menembusi meningkat,

tetapi selepas ia mencapai ketinggian tiang 80mm, kekuatan ricih menurun sedikit dan ia

disokong oleh idea 'panjang tiang kritikal'. Dapat disimpulkan bahawa parameter kekuatan

ricih terjejas oleh garis pusat dan ketinggian tiang dan kehadiran tiang PP banyak

meningkatkan kekuatan ricih.

viii

TABLE OF CONTENTS

Page

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

DEDICATION iv

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xii

LIST OF FIGURES xiv

LIST OF APPENDICES xviii

LIST OF SYMBOLS xix

LIST OF ABBREVIATIONS xxi

CHAPTER 1 INTRODUCTION

1.1 Background of Research 1

1.2 Problem Statement 5

1.3 Objectives 6

1.4 Scope of Study 6

1.5 Research Significance 8

CHAPTER 2 LITERATURE REVIEW

2.1 Soft Clay 10

2.1.1 Compressibility and Consolidation 12

2.1.2 Shear Strength 14

2.2 Polypropylene (PP) 16

ix

2.2.1 Particle Size 17

2.2.2 Specific Gravity 22

2.2.2 Compaction 23

2.2.4 Shear Strength and Tensile Strength 27

2.2.5 Permeability 30

2.2.6 Compressibility 31

2.3 Vertical Granular Column 33

2.3.1 Shear Strength 34

2.3.2 Consolidation Around Vertical Granular Column 37

2.3.3 Stress Strain Behavior 39

CHAPTER 3 METHODOLOGY

3.1 Introduction 43

3.2 Laboratory Works 45

3.3 Laboratory Tests For Determination of Physical Properties 46

3.3.1 Atterberg Limit Test 46

3.3.2 Specific Gravity Test 48

3.3.3 Sieve Analysis Test 49

3.3.4 Hydrometer Test 50

3.3.5 Relative Density Test 51

3.4 Laboratory Tests for Determination of mechanical Properties 52

3.4.1 Standard Compaction Test 53

3.4.2 Falling Head Permeability Test 54

3.5 Reinforcing Soft Kaolin Clay with Group Crushed PP Columns 56

3.5.1 Samples Preparation 56

3.5.2 Installation of PP Columns 58

3.5.3 Unconfined Compression Test (UCT) 62

x

CHAPTER 4 RESULTS AND DISCUSSIONS

4.1 Background 64

4.2 Physical Properties 65

4.2.1 Atterberg Limit Test 66

4.2.2 Specific Gravity Test 68

4.2.3 Particle Size Distribution 69

4.2.4 Relative Density Test 71

4.3 Mechanical Properties 72

4.3.1 Standard Compaction Test 72

4.3.2 Falling Head Permeability Test 74

4.4 Reinforcing Soft Kaolin Clay With Group Crushed PP Columns 75

4.4.1 Effect of PP Columns on shear Strength 75

4.4.2 The Effect of Area Replacement Ratio 85

4.4.3 The Effect of Column Penetration Ratio 88

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusion 91

5.2 Recommendation 93

REFERENCES 94

APPENDICES 98

A Properties of Polypropylene 98

B Atterberg Limit Test 99

C Specific Gravity Test 101

D Sieve Analysis Test 102

E Hydrometer Test 104

F Relative Density Test 106

G Standard Compaction Test 108

xi

H Falling Head Permeability Test 110

I Unconfined Compression Test 112

xii

LIST OF TABLES

Table No. Title

Page

1.1 Consumption rate for different types of plastics resin per day of the

respondent companies

4

1.2 Samples with Different Variables

8

2.1 General clay characteristics

12

2.2 Typical value of compression index of different type of soil offered

by Prof. Juan M. Pestana-Nascimento

14

2.3 Mechanical properties of the compaction

26

2.4 Range of Saturated Hydraulic Conductivity of Various Soil Material

30

2.5 Permeability value of PP to various gaseous

31

2.6 Comparison of the pressure response of similar semi-crystalline

polymers with different volume (room temperature)

32

2.7 Result of Unconfined Compression Test for group columns with

different height of columns

42

3.1 Summary of Laboratory Testing Program

45

3.2 Sample with variables of crushed PP installation

59

3.3 Summarization of the area replacement ratio calculations for 100

mm height of column

62

4.1 Basic properties of kaolin clay and PP

65

4.2 Specific gravity value for several type of soils

69

4.3 Type of soil with its unit weight

73

4.4 Permeability coefficient for different soils

74

4.5 Average value of shear strength for controlled sample

76

4.6 Average value of shear strength for reinforced column of 6 mm

diameter and 60 mm height

77

xiii



78



79



81



82



83

4.12 Summary of Analysis on Unconfined Compression Test

84

4.13 Effect of area replacement ratio for fully penetrating columns of

several studies

86

xiv

LIST OF FIGURES

Figure No. Title

Page

1.1 Installation of granular column

2

1.2 Consumption rate of plastics according to resin types

4

1.3 Unconfined Compression Test (UCT)

7

2.1 Quaternary Sediments in Peninsular Malaysia

11

2.2 The Relationship between Void Ratio, e and Log P for Normally

Consolidated and Overconsolidated Soil

13

2.3 Strength of Klang Clay

15

2.4 Crushed PP in pellet form

17

2.5 The Scanning Electron Microscopy photographs of PP powder

18

2.6 Particle size distribution of ELTEX P powders with different

grade

19

2.7 Particle size distribution between ELTEX P powder, other

commercial powders and group PP pellets

20

2.8 (a) SEM photomicrograph of morphology

(b) Particle size distribution of HPP-plastomer blend

21

2.9 (a) SEM photomicrograph of morphology

(b) Particle size distribution of HPP-EPR blend

22

2.10 (a) Comparison of specific gravities of fibres

(b) 1 kg of PP of equivalent coverage yields 20-41% more yarn

than other fibres, giving higher yield for the same weight

23

2.11 Effects on compaction on pore space

24

2.12 Moisture-density curve of soil for a given compactive effort

25

2.13 The effect of PP on shear strength of sand under normal load 28

kPa

29

xv

2.14 The effect of PP on the shear strength of the sand under three

different normal loads

29

2.15 Stone Column Installation

33

2.16 Effect of column height over column diameter ratio on

undrained shear strength

35

2.17 Column arrangement

36

2.18 Mechanisms of load transfer for (a) rigid pile and (b) a stone

column

37

2.19 Consolidation response for a group of columns

38

2.20 Excess pore pressure during consolidation

39

2.21 The variation of deviatoric stress and volumetric strain with

axial strain (a) Ac/As=7.9% (b) Ac/As=17.8% (c) Ac/As=31.2%

40

3.1 Flowchart of Project Methodology

44

3.2 Cone Penetration Method

47

3.3 Small pycnometers are leaved under vacuum

49

3.4 (a) Sieve shaker (b) Sieve analysis set

50

3.5 Equipment set up for the hydrometer test

51

3.6 Relative Density Test Equipment set up on vibrating table

52

3.7 The typical apparatus of the standard proctor test that are

standard compaction mold (left) and standard compaction

hammer (right)

54

3.8 The setup of apparatus for falling head test

55

3.9 Preparation of samples using customized mold

57

3.10 Drilling process of specimen

58

3.11 (a) Detailed arrangement of columns for diameter of 6 mm

(b) Detailed arrangement of columns for diameter of 10 mm

60

xvi

3.12 (a) 2D arrangement of columns with 6 mm diameter of PP

column

(b) 2D arrangement of columns with 15 mm diameter of PP

column

61

3.13 (a) Before installation of PP columns into the kaolin clay

(b) After installation of PP columns into the kaolin clay

62

3.14 Equipment set up for unconfined

63

4.1 Graph of penetration versus moisture content for liquid limit test

67

4.2 Plasticity Chart

68

4.3 Particle Size Distribution of Kaolin

70

4.4 Particle Size Distribution of PP

71

4.5 Dry unit weight versus average moisture content of kaolin

73

4.6 Relationship of strain and stress for controlled sample

76

4.7 Relationship of strain and stress for reinforced column of 6 mm


78



79



80



81



82



83

4.13 Improvement of shear strength versus area replacement ratio,

Ac/As

85


diameter with 60 mm, 80 mm and 100 mm height

87

xvii


diameter with 60 mm, 80 mm and 100 mm height

87

4.16 Improvement of shear strength versus column penetration ratio,

Hc/Hs

88


and 10 mm diameter with 60 mm height

89



90



90

xviii

LIST OF APPENDICES

Appendix Title

Page

A

Properties of Polypropylene 98

B Atterberg Limit Test

99

C Specific Gravity Test

101

D Sieve Analysis Test

102

E Hydrometer Test

104

F Relative Density Test

106

G Standard Compaction Test

108

H Falling Head Permeability Test

110

I

Unconfined Compression Test

112

xix

LIST OF SYMBOLS

Ac Area of column

As Area of sample

c Cohesion

Cc Compression index

Cc Coefficient of gradation

Cu Uniformity coefficient

e Void ratio

ε Strain

Gs Specific gravity

Hc Height of column

Hs Height of sample

i Hydraulic gradient

k Permeability coefficient

m Moisture content

Se Elastic settlement

Sc Primary consolidation settlement

Ss Secondary consolidation settlement

ST Total settlement

Pc Maximum pressure the soil has been subjected to in past

ρd Dry density

ρd-max

Maximum dry density

ρd-min Minimum dry density

xx

q Deviator stress

qmax Maximum deviator stress

Rd Relative density

So Sorting coefficient

su Undrained shear strength

v Velocity

γd Dry unit weight

γt Wet unit weight

γsat Saturated unit weight

φ Angle of internal friction

σ Normal stress

xxi

LIST OF ABBREVIATIONS

ABS Acrylonitryl Butadien Styrene

AASHTO

American Association of State Highway and Transportation

Officials

ASTM American Society for Testing and Materials

BS British Standard

BSCS British Soil Classification System

CL Clay low plasticity

CH Clay high plasticity

EPR Ethylene-propylene rubber

FYP Final Year Project

HDPE High-density polyethylene

HPP Homo-polymer Polypropylene

LL Liquid limit

LDPE Low-density polyethylene

MDPE Medium-density polyethylene

MH Silt high plasticity

ML Silt low plasticity

MPMA Malaysian Plastics Manufacturer Association

NP Non-plastic

PC Polycarbonate

PE Polyethylene

PI Plasticity index

http://en.wikipedia.org/wiki/American_Association_of_State_Highway_and_Transportation_Officials

http://en.wikipedia.org/wiki/American_Association_of_State_Highway_and_Transportation_Officials

xxii

PL Plastic limit

PP Polypropylene

PS Polystyrene

PT Peat

SL Shrinkage limit

UCT Unconfined Compression Test

USCS Unified Soil Classification System

CHAPTER 1

INTRODUCTION

1.1. BACKGROUND OF RESEARCH

Recently, due to urbanization and industrialization that increase the development,

the building construction such as housing and commercial are being built massively. Soft

clays exist in most coastal plains of Peninsular Malaysia and all land including soft soil has

to utilize to overcome the massive construction. Clay is widely distributed, abundant

mineral resources of major industrial importance for an enormous variety of uses (Ampian,

1985). Development of activities on those sites such as road embankment, earth dams and

others involve problems of stability and excessive settlement. There are many available

methods to improve the properties of soft clay soil since this type of soil usually causes

problems to the civil engineer as it has high compressibility and low shear strength.

The settlement behavior of soil must be understand to find the solution for it

because it may impose stability problem to the superstructure where the rate of settlement

is different all over the area of the developed ground if the uneven settlement occurred.

Uneven settlement might cause toppling of the said superstructure, meanwhile for uniform

settlement, foundation settlement problem can occur in excessive settlement (Halim, 2012).

Thus, settlement of soil must be solved before the superstructure being constructed.

Therefore, ground improvement techniques may be necessitated to modify the soil

properties. There are many available methods to improve the properties of soft clay such as

sand drain, piling, stone (granular) column, using admixtures and many more. Recently,

2

stone column are gaining acceptances in geotechnical field and have been widely used all

around the world including Malaysia. This method is applied commonly for road

embankments and railway area, lightly loaded foundation, and storage tanks (Murugesan

and Rajagopal, 2010). Besides it promotes the compaction of the soil and allows water to

rise up by acting as a channel, additional bearing capacity is also provided to the soil.

This Final Year Project (FYP) concentrates on the strength of soft clay reinforced

with group crushed Polypropylene (PP) columns. Basically, concept of crushed PP columns

with stone column is the same, but the result from this process is slightly different depends

on the properties of the PP itself. However, this ground improvement technique has been

successfully applied to reduce the settlement as well as increasing the bearing capacity of

the soils and accelerating the settlement process (Ambily and Gandhi, 2007).

Previous studies have been proven that when the granular column is inserted into

soft soil as shown in Figure 1.1, a composite soil mass that has a greater strength and

improved stiffness will be produced compared to the unreinforced soil. The columns act as

piles that transfer the structure load to greater depth. Thus, this is one of the most practical

techniques to improve the mechanical properties of soft soil (Black et al., 2007).

Figure 1.1: Installation of granular column

Source: Juan Manuel et al. (2010)

3

PP is a thermoplastic which means those materials can be melted again and again

and also can be heated to a certain temperature and will harden again as they cool. It has an

intermediate level of crystallinity which located between low-density polyethylene (LDPE)

and high-density polyethylene (HDPE). It is known for its low strength to density ratio

compared to HDPE and LDPE which the density can range from 0.90 to 0.92 g/cm3. PP

yields the greatest volume of fibre for a given weight because of its low specific gravity

which means that PP provides good bulk and cover while being lighter in weight. The

porous PP molecule has a series of CH3 groups that oriented on one side of the carbon

backbone which is making PP stiffer, creates higher degree of crystallinity and more

resistance to the tendency to flow under stress as compared to polyethylene (PE). It is also

harder and more opaque to withstand somewhat higher temperature up to 160 °C, or 320 °F

without melting.

The rapid economic growth in Malaysia has generated 0.5-08 kg waste

material/person/day and in rural areas the figure increased to 1.7 kg/person/day (Kathirvale

et al., 2003). The authors noted that plastics materials constitute the largest component of

waste material by weight at 18.9 %, apart from food and paper. Findings from study

indicated that plastics materials are disposed at rate of 2.943 kg/day, an approximation of 5

% from the daily consumption of plastics material. This finding is in agreement with the

results obtained by Rossbach (1979) at 5.3 %. The results from Malaysian Plastics

Manufacturer Association (MPMA) (2004) clearly indicated that polyolefin such as

polypropylene (27 %) and polyethylene (10 %) monopolized the plastics industry in

Malaysia and it reported that the consumption of poly olefins as the highest, at 67.7 %.

Figure 1.2 and Table 1.1 show the consumption rate for different types of plastics resin

(MPMA, 2004). Currently, the recycling and fully utilization of waste materials have

attracted great attention in construction field to fulfill the current interest in long term and

sustainable development, as well as to reduce the cost of managing the landfill.

4

Table 1.1: Consumption rate for different types of plastics resin per day of the respondent

companies

Plastic resin kg day-1

Polypropylene (PP) 12827

Polyethylene (PE) 4588

Polystyrene (PS) 9413

Polycarbonate 1825

Acrylonitrile butadiene styrene (ABS) 13218

Others 4966

Total consumption per day 46837

Source: Malaysian Plastics Manufacturers Association, MPMA (2004)

Figure 1.2: Consumption rate of plastics according to resin types

Source: Malaysian Plastics Manufacturers Association, MPMA (2004)

http://www.mpma.org.my/

5

1.2. PROBLEM STATEMENT

Chen and Morriss (2000) stated that the design of foundation on soft clay has been

the concern of engineers since the beginning of soil engineering. Therefore, structures

constructed on soft soils may experience excessive settlements, large lateral flow and slope

stability (Abdullah and Edil, 2007). This has leads to the findings and applications of

various type of ground improvement, for example granular columns. This technique is

preferable because it gives the advantage of reduced settlements and accelerated

consolidation settlements due to reduction in flow path lengths. One of the major factors

that could lead to high settlement is the high compressibility properties of soft clay. This

condition due to finer particles of soft clay and the presence of water make it being too

cohesive. High settlement is so dangerous because it affects the movement of whole

structure and end up with structure failures.

Due to the rapid development of building construction and highway infrastructure,

the settlement of soft soil become one of the main problems for foundation design. For

example, there is an increase of stress in the soft ground as well as the strain or settlement

when a road embankment is constructed over soft ground. Excessive yielding in vertical

and lateral direction of the soft ground will occur if the surcharge load due to filling and

constructions traffic load is high near the ultimate bearing capacity of the supported soft

ground. Moreover, this situation will followed by tension crack, deep seated rotational or

translational slip when the deformation is large and extensive.

Therefore, in this study, the strength of soft soils reinforced with group crushed PP

as replacement material in granular column had been investigated. Expecting the analysis

result may give the positive progress to the soil improvement such as the undrained shear

strength of sample reinforced was greatly improved compared with that of the unreinforced

samples. Indirectly, it will solve the PP disposal problem by reusing the material to

reinforce the soft soils, besides, the landfill in Malaysia also have been limited due to the

increasing of daily waste. Furthermore, since the PP is a waste material, the cost of soil

6

improvement can be reduce and hopefully the analysis result will help to make further

progress to the soil improvement of the soft clay.

1.3. OBJECTIVES

The aim of this study is to investigate the strength of soft clay reinforced with group

crushed PP columns. The soft clay has been represented by compacting kaolin paste. This

study is carried out to achieve the objectives as follow:

i. To determine the physical characteristics of kaolin clay and PP and

morphological characteristics of PP;

ii. To determine the undrained shear strength of soft clay reinforced with

various dimensions of group PP columns.

1.4. SCOPE OF STUDY

The materials used in this study were kaolin as soil sample and crushed PP as

reinforcing columns. To determine the physical properties of kaolin and PP and the

morphological characteristics of PP, the following laboratory tests were carried out:

i. Atterberg Limit Test

ii. Specific Gravity Test

iii. Sieve Analysis Test

iv. Hydrometer Test

v. Relative Density Test

vi. Standard Compaction Test

vii. Falling Head Permeability Test

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