COMPARATIVE STUDY OF THE SHRINKAGE CHARACTERISTICS OF
PEAT AT SOUTH EAST JOHORE
NURSYAHIDAH BINTI SAEDON
A thesis submitted for partial fulfilment of the requirement for the award of
Masters in Civil Engineering
Faculty of Civil and Environmental Engineering
Universiti Tun Hussein Onn Malaysia
JUNE 2016
UNIVERSITI TUN HUSSEIN ONN MALAYSIA
STATUS CONFIRMATION FOR MASTER PROJECT THESIS
COMPARATIVE STUDY OF THE SHRINKAGE CHARACTERISTICS OF
PEAT AT SOUTH EAST JOHORE
ACADEMIC SESSION: 2016/2017
I, NURSYAHIDAH BINTI SAEDON, agree to allow this Master Project Thesis to
be kept at the Library under the following terms:
1. This Master Project Report is the property of the Universiti Tun Hussein Onn Malaysia .
2. The library has the right to make copies for educational purposes only.
3. The library is allowed to make copies of this report for educational exchange between their
higher educational institutions.
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NURSYAHIDAH BINTI SAEDON
48, JALAN GELAM 2,
TAMAN RINTING,
81750 JOHOR BAHRU,
JOHOR
Date :
Approved by,
ASSOC. PROF. DR. ADNAN BIN
ZAINORABIDIN
Date :
√
iii
DECLARATION
I hereby declare that the work in this thesis is my own except for quotations and
summaries which have been duly acknowledged
Student : …………………………………………..
NURSYAHIDAH BINTI SAEDON
Date : JUNE 2016
Supervisor : …………………………………………….
ASSOCIATE PROFESSOR DR. ADNAN BIN
ZAINORABIDIN
iv
DEDICATION
I wish to dedicated and thankful to Almighty Allah though whose grace and mercy, I
have survived till the end.
For my beloved Ayah, Emak and Ibu
Mr. Saedon B. Majid, Mdm. Halijah Bt. Salleh and Mdm. Mastura Bt. Ismail
My Supervisor
Associate Professor Engr. Dr. Adnan bin Zainorabidin
My Siblings
Nurhana, Nurhuda, Muhamad Nur Safwan, Muhammad Nur Hakimi and Mohammad
Nur Syahmi
My Special Friends
Daing Abdul Razzaq bin Mohd Nasir
My Friends
Siti Nooraiin, Nurul Nadia, Amira, Siti Noor Aini, Nor Amalina, Hawa Haidar
v
ACKNOWLEDGEMENT
In the name of Allah, the Most Gracious and the Most Merciful,
Alhamdulillah, all praises to Allah for the strengths and His blessing in completing
this thesis. Special appreciation goes to my supervisor, Assoc. Prof. Dr. Adnan bin
Zainorabidin, for his supervision, enthusiastic guidance, and encouragement in all
aspects during completing this project. His invaluable help of constructive comments
and suggestions throughout the experimental and thesis works have contributed to the
success of this research.
I would like to express my appreciation to the staff of Research Centre of Soft
Soil (RECESS), UTHM, Mrs. Salina, Mr. Amir and Mr. Muzaffar Syah for their
support and assisting in my laboratory work. Not forgotten to RECESS postgraduate
students for their support, co-operations and help towards my master project affairs.
My deepest gratitude to my beloved parents and also to my siblings for their
love, prayers, support and encouragement. Last but not least, sincere thanks to all my
friend for their kindness and moral support during my study. For those who directly or
indirectly contributed in this study, thank you very much.
vi
ABSTRACT
This study is to review the behaviour of peat under reconstituted sample and
undisturbed soil and to investigate shrinkage behaviour using modified techniques.
Three different locations have been selected which are Parit Nipah, Batu Pahat and
Integrated Peat Research Station (IPRS), Pontian for peat soil, while clay soil is
collected from the Research Centre of Soft Soil (RECESS), UTHM. For modified
techniques of measuring shrinkage, peat samples were prepared in different diameter
sizes (50mm, 70mm and 100mm) and temperatures (air-dried, 60C and 105C).
Undisturbed samples were compared with reconstituted sample that had been obtained
by wet sieve and dry sieve procedures (particles that passing 0.300mm and 0.425mm).
Reconstituted sample was also dried with two different temperatures. It is significant
in comparing the shrinkage characteristics by using a modified techniques with the
British standard method. In Von post classification system, Parit Nipah and Pontian
peat soil had been classified as H5 and H4. The results of the index properties tests of
Parit Nipah, Pontian peat soil and RECESS clay soil had been analysed. Most of the
shrinkage values show that reconstituted samples that had been prepared in wet
condition with particle sizes passing 0.300mm is nearly same with undisturbed
samples. It is also shows that particle sizes with passing 0.300mm sieve has higher
absorption rather than 0.425mm. Thus, it shows that, smaller particle sizes give higher
results of volumetric/linear shrinkage and loss of water. It was found that higher
temperature was not necessarily in the volume changes of the soil sample. It also can
be concluded that the shrinkage of peat soil that had been prepared in wet condition is
more compatible with undisturbed peat soil and natural state condition on field site.
Fibre of peat sample gives huge factors of the effect to the volume changes and
shrinkage measurement.
vii
ABSTRAK
Kajian ini adalah untuk mengkaji kelakuan tanah gambut bagi sampel tanah yang
terganggu dan tanah tidak terganggu. Ia juga bagi menyiasat pengecutan tanah gambut
menggunakan teknik baru yang telah diubah suai. Tiga lokasi yang berbeza telah
dipilih iaitu Parit Nipah dan Stesen Penyelidikan Tanah Gambut (IPRS), Pontian untuk
tanah gambut, manakala tanah liat diambil dari Pusat Penyelidikan Tanah Lembut
(RECESS), UTHM. Untuk teknik baru yang diubah suai dalam pengukuran
pengecutan tanah, sampel tanah gambut disediakan dalam berbeza saiz diameter
(50mm, 70mm dan 100mm) dan suhu (suhu bilik, 60°C dan 105°C). Sampel tidak
terganggu dibandingkan dengan sampel semula yang telah disediakan dengan prosedur
ayak basah dan kering (partikel yang melepasi 0.300mm dan 0.425mm).Sampel yang
terganggu telah dikeringkan melalui dua suhu yang berbeza. Ia penting dalam
mengukur pengecutan tanah dengan menggunakan kaedah baru yang diubah suai
berbanding dengan kaedah Standard British. Merujuk kepada sistem klasifikasi Von
Post, sampel di Parit Nipah dan Pontian dikelaskan sebagai H5 dan H4. Sifat asas ujian
Parit Nipah, Pontian tanah gambut dan tanah liat RECESS telah dianalisis. Sebahagian
besar pengecutan tanah gambut menunjukkan bahawa sampel semula yang disediakan
dalam keadaan basah dengan saiz partikel 0.300mm seakan selari dengan sampel tidak
terganggu. Ia juga menunjukkan saiz zarah 0.300mm menyerap lebih cepat daripada
0.425mm. Oleh itu, ia menunjukkan bahawa, saiz partikel yang lebih kecil
memberikan nilai yang tinggi bagi isipadu pengecutan dan kehilangan air. Didapati
bahawa suhu yang tinggi tidak semestinya menjadi faktor utama dalam perubahan
isipadu sampel tanah. Ia juga boleh disimpulkan bahawa pengecutan tanah yang telah
disediakan dalam keadaan basah lebih serasi dengan tanah gambut terganggu dan
keadaan semula jadi di tapak lapangan. Kandungan serat sampel tanah gambut akan
memberikan kesan yang tinggi kepada perubahan isipadu dan pengukuran pengecutan.
viii
TABLE OF CONTENTS
TITLE i
STATUS OF CONFIRMATION ii
DECLARATION iii
DEDICATION iv
ACKNOWLEDGEMENT v
ABSTRACT vi
ABSTRAK vii
TABLE OF CONTENTS viii
LIST OF TABLES xii
LIST OF FIGURES xiv
LIST OF EQUATIONS xvii
LIST OF ABBREVIATIONS xviii
LIST OF APPENDIXES xix
CHAPTER TITLE PAGES
CHAPTER 1 INTRODUCTION
1.1 Background of thesis 1
1.2 Problem Statement 3
1.3 Objectives of study 6
1.4 Aim of study 6
1.5 Scope of study 7
1.6 Outline of thesis 8
ix
CHAPTER 2 LITERATURE REVIEW
2.1 Peat
2.1.1 Peat in the Malaysia 10
2.1.2 Properties of peat soil 12
2.2 Clay soil in Malaysia 16
2.3 Shrinkage Characteristics
2.3.1 Definition of Shrinkage Measurement 21
2.3.2 Shrinkage Process 23
2.3.3 Shrinkage of Peat Soil 24
2.3.4 Shrinkage of an Inorganic Soil 27
2.4 Methods of soil sampling 30
2.5 Summary of chapter 34
CHAPTER 3 RESEARCH METHODOLOOGY
3.1 Introduction 35
3.2 Sampling Method 38
3.2.1 Disturbed sampling 38
3.2.2 Undisturbed sampling 38
3.3 Laboratory testing method 41
3.3.1 Moisture Content by Standard Procedure 42
3.3.2 Moisture Content (different temperature - 60°C) 43
3.3.3 Specific Gravity 43
3.3.4 Liquid limit 45
3.3.5 Rolling hand (Plastic Limit for clay) 47
3.3.6 Organic Content 48
3.3.7 Fibre Content 48
3.4 Sampling Preparation of Shrinkage Measurement
3.4.1 Standard Linear Shrinkage 50
3.4.2 Modified Linear Shrinkage 52
3.5 Summary of chapter 54
x
CHAPTER 4 RESULTS AND CRITICAL ANALYSIS
4.1 Introduction 55
4.2 Physical Characteristic 56
4.3 Index Properties Test Result 57
4.3.1 Moisture Content 59
4.3.2 Specific Gravity 60
4.3.3 Organic Content 61
4.3.4 Fibre content 61
4.3.5 Liquid Limit 62
4.4 Shrinkage Analysis
4.4.1 Bar Linear Shrinkage Method 66
(BS1377: Part 2: 1990: 6.5)
4.4.2 Modified Linear Shrinkage
4.4.2.1 Undisturbed sample preparation 68
(different sizes and different temperature)
4.4.2.1.1 Relationship of volume changes 68
of sample to the temperature effect
4.4.2.1.2 Relationship of water loss to the 73
temperature effect
4.4.2.1.3 Relationship of shrinkage measurement 75
(horizontal) to the temperature effect
4.4.2.2 Reconstituted sample preparation 79
4.4.2.2.1 Relationship of volume changes of 80
sample to the temperature effect
4.4.2.2.2 Relationship of water loss to the 86
temperature effect
4.4.2.2.3 Relationship of shrinkage measurement 92
to the temperature effect
4.4.3 Other research contributions
4.4.3.1 Different compositions in 50mm diameter 102
of undisturbed samples
4.4.3.2 Further Investigation of Soil Volume Changes 104
xi
at Four Dimensional Points for Undisturbed
Samples of Parit Nipah and Pontian peat
4.4.4 Detailing shrinkage measurements
4.4.4.1 Undisturbed samples 106
4.4.4.1.1 Parit Nipah peat sample 106
4.4.4.1.2 Pontian peat sample 107
4.4.4.2 Reconstituted samples 109
4.4.4.2.1 Parit Nipah peat sample 109
4.4.4.2.2 Pontian peat sample 111
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Introduction 115
5.2 Discussions 115
5.2.1 Objective 1: The behaviour of peat under 117
reconstituted and undisturbed samples condition
5.2.2 Objective 2: An investigation the characterization 120
shrinkage behaviour by modified techniques in
preparing samples and shrinkage measurement
techniques
5.2.3 Objective 3: Established the shrinkage behaviour of 123
peat by comparing reconstituted (samples with passing
sieve 0.300mm and 0.425mm) and undisturbed sample
that has variable particle sizes
5.3 Conclusion 124
5.4 Further recommendation 127
REFERENCES
xii
LIST OF TABLES
NO. TITLE PAGES
1.1 Outline of the study 8
2.1 The distribution of peat land and organic soil in Malaysia 11
(Hashim and Islam, 2008)
2.2 Properties of peat soil based on types of peat 13
2.3 The Von Post Scale of Humidification (source Ekono, 1981) 14
2.4 Properties of peat soil of some areas in Malaysia 16
2.5 Classification of clay soil in Malaysia (Balasubramaniam et al, 1985) 17
2.6 Thickness of clay soil in Peninsular Malaysia (Abdullah and 17
Chandra, 1987)
2.7 Characteristics of clay soil classification in Peninsular Malaysia 19
(Tajuddin, 2004)
2.8 Average annual subsidence of peat at different locations in the 27
Waikato Region
2.9 Probable Expansion as Estimated from Classification Test Data 29
(Holtz and Kovacs, 1981)
3.1 Type of tube sampling and related tests for each location 41
3.2 Summary of testing parameter and conditions (Zainorabidin, 2011) 41
3.3 USDA classification of peat 49
3.4 Numbers of the sample for reconstituted sample that was prepared by 53
wet sieving method
3.5 Numbers of the sample for reconstituted sample that was prepared by 53
dry sieving method
3.6 Numbers of the undisturbed sample for this testing 54
4.1 Typical results of index properties of peat soil 58
4.2 Typical results of index properties of clay soil 58
4.3 Specific gravity of peat and clay soil 60
xiii
4.4 Organic content of peat soil 61
4.5 Fibre content of peat soil 62
4.6 Liquid limit of Parit Nipah peat soil 63
4.7 Liquid limit of Pontian peat soil 64
4.8 Liquid limit of RECESS clay soil 65
4.9 Linear shrinkage of Parit Nipah peat soil 67
4.10 Linear shrinkage of Pontian peat soil 67
4.11 Linear shrinkage of RECESS clay soil 67
4.12 Volumetric shrinkage of Parit Nipah and Pontian peat due to temperature 71
4.13 Loss of water on Parit Nipah and Pontian peat sample due to temperature 73
4.14 Linear shrinkage of Parit Nipah and Pontian peat due to temperature 79
effect
4.15 Volumetric shrinkage on Parit Nipah and Pontian peat sample due to 86
temperature effect
4.16 Loss of water on Parit Nipah and Pontian peat sample due to temperature 91
effect
4.17 Linear shrinkage of Parit Nipah reconstituted peat sample 92
4.18 Linear shrinkage of Pontian reconstituted peat sample 98
4.19 Shrinkage observation that contains different compositions 102
4.20 Detailing shrinkage measurements of Parit Nipah undisturbed samples 106
4.21 Detailing shrinkage measurements of Pontian undisturbed samples 107
4.22 Detailing shrinkage measurements of Parit Nipah reconstituted samples 109
4.23 Detailing shrinkage measurements of Pontian reconstituted samples 111
5.1 Volumetric shrinkage on reconstituted samples of Parit Nipah and 121
Pontian peat soil
5.2 Volumetric shrinkage of undisturbed sample of Parit Nipah and 121
Pontian peat due to temperature effect
5.3 Different structure of reconstituted samples between 0.300mm and 123
0.425mm in dry condition
5.4 Index properties of peat and clay soil 124
5.5 Linear shrinkage of undisturbed peat sample due to temperature effect 125
5.6 Linear shrinkage of reconstituted peat sample due to temperature effect 125
xiv
LIST OF FIGURES
NO. TITLE PAGES
1.1 The Holme Post, today and in the past (Waltham, 2000) 2
1.2 Land subsidence on one of the houses in Kampung Parit Nipah, 4
Batu Pahat
1.3 Poor road conditions in Kampung Parit Nipah, Batu Pahat as a 5
result of subsidence caused by shrink-swell behaviour.
1.4 Longitudinal cracking on a rural road in Lincolnshire as a result of 5
clay-related subsidence. Credit photo: O. Pritchard. (Pritchard, 2015)
2.1 Peat land distribution in Semenanjung Malaysia (642,857 ha) 11
(Hashim and Islam, 2008)
2.2 Definition of shrinkage limit of clay soil (Holtz and Kovacs, 1981) 21
2.3 Shrinking Soil Mechanism 24
2.4 The record of ground subsidence on the peat within 150 years at 25
the Holme Post which is correlated with water table (Waltham, 2000)
2.5 Conceptual model describing the development of primary, secondary 28
and tertiary cracks, resulting from the build-up of tensile stresses
on drying (Taboada, 2003)
3.1 Actual work procedure in this study 36
3.2 Method of collecting undisturbed sample 40
3.3 Specific gravity testing procedure 44
3.4 Apparatus for cone penetrometer liquid test 45
3.5 Peat soil preparation of bar linear shrinkage 51
3.6 Procedure of modified shrinkage measurement of undisturbed sample 53
4.1 Illustration of peat and clay soil composition (a) Parit Nipah peat 57
soil; (b) Pontian peat soil; and (c) RECESS clay soil
4.2 Graph of penetration against moisture content for Parit Nipah 64
peat soil
xv
4.3 Graph of penetration against moisture content for Pontian 65
peat soil
4.4 Graph of penetration against moisture content for RECESS 66
clay soil
4.5 Volume changes with various temperature for Parit Nipah peat soil 68
(50mm, 75mm and 100mm diameter of samples)
4.6 Volume changes with various temperature for Pontian peat soil 69
(50mm, 75mm and 100mm diameter of samples)
4.7 Volume changes of 50mm diameter of sample with different 71
temperature for Parit Nipah (PPN) and Pontian (PN) peat soil
4.8 Volume changes of 75mm diameter of sample with different 72
temperature for Parit Nipah (PPN) and Pontian (PN) peat soil
4.9 Volume changes of 100mm diameter of sample with different 72
temperature for Parit Nipah (PPN) and Pontian (PN) peat soil
4.10 Water loss of Parit Nipah (PPN) and Pontian (PP) peat soil 73
with different temperature (50mm diameter size)
4.11 Water loss of Parit Nipah (PPN) and Pontian (PP) peat soil 74
with different temperature (75mm diameter size)
4.12 Water loss of Parit Nipah (PPN) and Pontian (PP) peat soil 74
with different temperature (100mm diameter size)
4.13 Linear shrinkage of Parit Nipah peat soil with different temperature 76
(a) 50mm diameter of samples; (b) 75mm diameter of samples; and
(c) 100mm diameter of samples
4.14 Linear shrinkage of Pontian peat soil with different temperature 77
(a) 50mm diameter of samples; (b) 75mm diameter of samples; and
(c) 100mm diameter of samples
4.15 Schematic drawing in dry and saturated conditions; 80
(i) sand; (ii) clay; and (iii) peat soil (Zainorabidin, 2010)
4.16 Volume changes for Parit Nipah reconstituted peat sample with 81
different drying temperature (a) air-dried; (b) 60°C; and (c) 105°C
4.17 Comparison of volumetric shrinkage for Parit Nipah reconstituted peat 83
sample with different drying temperature
4.18 Volume changes for Pontian reconstituted peat sample with different 84
drying temperature (a) air-dried; (b) 60°C; and (c) 105°C
xvi
4.19 Comparison of volumetric shrinkage for Pontian reconstituted 85
peat sample with different drying temperature
4.20 Moisture loss for Parit Nipah reconstituted peat sample with different 87
drying temperature (a) air-dried; (b) 60°C; and (c) 105°C
4.21 Comparison of moisture loss for Parit Nipah reconstituted peat 88
sample with different drying temperature
4.22 Moisture loss for Pontian reconstituted peat sample with drying 89
temperature (a) air-dried; (b) 60°C; and (c) 105°C
4.23 Comparison of water loss for Pontian reconstituted peat sample 90
with different drying temperature
4.24 Linear shrinkage for Parit Nipah reconstituted peat sample with 93
different drying temperature (a) air-dried; (b) 60°C; and (c) 105°C
4.25 Comparison of linear shrinkage for Parit Nipah reconstituted peat 95
sample with different drying temperature
4.26 Horizontal and vertical shrinkage for Parit Nipah reconstituted sample 96
4.27 Linear shrinkage for Pontian reconstituted peat sample with different 97
drying temperature (a) air-dried; (b) 60°C; and (c) 105°C
4.28 Comparison of linear shrinkage for Pontian reconstituted peat 100
sample with different drying temperature
4.29 Horizontal and vertical shrinkage for Pontian reconstituted sample 101
4.30 Changes in density for 50mm diameter size of PP sample 103
4.31 Changes in loss of moisture for 50mm diameter size of PP sample 103
4.32 Shrinkage measurement by point A, B, C and D 104
4.33 Diameter of Parit Nipah peat sample in 105⁰C for 24 hours 105
4.34 Diameter of Pontian peat sample in 105⁰C for 24 hours 105
5.1 Comparison between undisturbed and reconstituted samples for 118
Parit Nipah (PN) peat soil; (a) air-dried; (b) 60°C; and (c) 105°C
5.2 Comparison between undisturbed and reconstituted samples for 120
Pontian (PO) peat soil; (a) air-dried; (b) 60°C; and (c) 105°C
xvii
LIST OF EQUATIONS
NO. TITLE PAGES
2.1 Linear Shrinkage 22
2.2 Inside Clearance Ratio (ICR) 33
2.3 Area Ratio (AR) 33
3.1 Moisture Content 42
3.2 Specific Gravity 43
3.3 Plastic Limit 47
3.4 Ignition Loss 48
3.5 Fibre Content 49
3.6 Linear Shrinkage 52
xviii
LIST OF ABBREVIATIONS
AD Air-dried
AR Area Ratio
ASTM American Society for Testing and Materials Standard
AW Absorbed Water
BS British Standard Institution
CR Clay RECESS
FC Fibre Content (%)
GS Specific Gravity
ICR Inside Clearance Ratio
ICW Intercellular Water
IPRS Integrated Peat Research Station
IPW Interparticle Water
ISA Ideal Sampling Approach
LL Liquid Limit (%)
LOI Loss of Ignition (%)
LS Linear Shrinkage (%)
OC Organic Content (%)
PIV Particle Image Velocimetry
PL Plastic Limit (%)
PP Pontian Peat
PPN Parit Nipah Peat
PVC Polymerized Vinyl Chloride
RECESS Research Centre of Soft Soils
SL Shrinkage Limit (%)
USA United States of America
UTHM Universiti Tun Hussein Onn Malaysia
w Moisture Content (%)
xix
LIST OF APPENDICES
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
1
CHAPTER 1
INTRODUCTION
1.1 Background of thesis
Urbanisation leads to the utilization of very soft soil such as peat ground conditions,
especially in extensive peat areas such as Kampung Parit Nipah and Integrated Peat
Research Station (IPRS), Pontian. The behaviour and composition of peats are
accentuating the need for useful geotechnical design purposes and engineering
geological classification and assessment of the ground conditions (Zainorabidin and
Bakar, 2003; Zainorabidin et al.,2007).
Peat soil area is categorized as very unstable ground (Alwi, 2008; Deboucha et
al., 2008; Hashim and Islam, 2008; Duraisamy et al., 2008; Huat et al., 2011 and
Atemin, 2012). It is highly compressible and characterized to have very low shear
strengths and poor drainage characteristics (Duraisamy et al., 2008; Huat et al., 2011;
and Atemin, 2012).
The characterization and composition of peat that are not homogenous and high
fibrous content have a significant effect on behaviour as well as the strength of soil.
The physical characteristics such as high moisture content and organic content more
than 75% are the causes of stability problems (Masawi, 2010). It creates very
challenging construction problems, such as excessive time-dependent foundation
settlements, as well as bearing capacity and foundation failures (Fuleihan, 2015).
In many parts of the world, most of the countries that experienced seasonal
changes every year such as United Kingdom, USA and Japan are considered as
important and have potential economic significance with a shrink swell characteristics
of fine-grained soil. It can cause excessive damage to structure and road constructions
2
by shrinking swell characteristics which happen repetitively every year. This situation
is also called as the subsidence of soil.
For countries with no seasonal changes such as Malaysia, rainfall and hot
weather occur frequently significantly in shrink swell soil. It can cause cracking to the
building and heaving the roadways. For the property owners of buildings and roadways
who do construction on representative soil, they will face financial lost to repair the
affected houses.
According to Figure 1.1, it shows the emergence of the Holme Post from the
wasting peat, and there was subsidence from 1850’s to 2000’s even without any
loading. Waltham (2000) mentioned that it subsided about 4m and gave an impressive
record of the ground subsidence. Throughout the time, it was then slowed to a rate that
only recognisable over a decade or more; where the observations were clearly recorded
the ground movement since the peat was more drained which caused subsidence.
Figure 1.1: The Holme Post, today and in the past (Waltham, 2000)
However, sampling of the soil is also significant in obtaining more accurate
results by minimizing the degree of disturbance before the sampling is tested in the
laboratory. Further study and ground information were gathered as the most desired
research based on the appreciation of the type and the extent of challenging ground
3
conditions, especially subsidence by the shrinkage effect that exists on the test sites. It
gives difficulty to the construction of peat soils due to the fibre origin, temperature and
humidity. Apart of shrinkage effect, ground subsidence is also due to a combination of
consolidation and wastage, and it will cause a settlement to the soils.
1.2 Problem Statement
Peat as organic soil that is known as soft soil is widely distributed in Malaysia. It is
difficult to collect samples of peat soil due to the high fibre and groundwater level
especially an undisturbed sample.
For peat, shrinkage effect and some other important parts are important in
determining the strength and moisture content. It is a common cause to foundation
problems; especially in road construction. It is also contributed to the cause of
settlement of soil. The changes of moisture content may also due to periods of unusual
rain, changes in humidity or unusual drought. By referring to British Standard, oven
dried temperature for a soil is 105 ± 5 C. However, it will be a problem to the peat
soil because of its composition with high fibre content that consists of root and wood
decayed.
It is significant to observe the shrinkage effect especially when a property
subsides it can cause significant cracking and damage to the property. For affected
areas such as Parit Nipah, buildings that were constructed with piling were floated
while buildings without piling were cracked. However, shrinkage which taking into
account on climate change is likely to result in more frequent occurrence of
subsidence.
4
Figure 1.2: Land subsidence in one of the houses in Kampung Parit Nipah, Batu
Pahat
Infrastructure such as roadways was also affected by clay-related subsidence
that was caused by shrinkage effect. Road networks were also susceptible to
subsidence. As in Figure 1.3 and 1.4, it can result in severe longitudinal cracking of
pavements and making poor driving conditions. Since the roadways were constructed
using piling methods, the pile can emerge from the road when it was subsidised.
5
Figure 1.3: Poor road conditions at Kampung Parit Nipah, Batu Pahat as a result of
subsidence that possibly caused by shrink-swell behaviour
Figure 1.4: Longitudinal cracking on a rural road in Lincolnshire as a result of clay-
related subsidence. Credit photo: O. Pritchard. (Pritchard, 2015)
6
1.3 Objectives of Study
The objectives of this study are:
1. To review the behaviour of Parit Nipah and Pontian peat under
reconstituted and undisturbed conditions.
2. To investigate the characterization of shrinkage behaviour by modified
techniques in preparing samples and shrinkage measurement techniques.
3. To establish the shrinkage behaviour of peat by comparing reconstituted
(samples that passing sieve at 0.300mm and 0.425mm) and undisturbed
samples.
1.4 Aim of the study
The purpose of the study is to review the shrinkage behaviour of peat under
reconstituted sample and undisturbed sample with different techniques and
temperatures. A modified method of using two different grain sizes was compared with
undisturbed sample. According to the British Standard, the sample preparation for
linear shrinkage testing used particle sizes that passing 0.425mm. However, in real
condition of peat soils, it was composed to various particle sizes and most of the peat
soil particles were formed by decayed plants that are larger than 0.425mm. Moreover,
the shrinkage characteristics were observed by two different techniques which are in
accordance to British standard which is bar linear shrinkage method and modified
shrinkage techniques. Modified shrinkage techniques were conducted directly on
undisturbed samples of the tube sampler in order to retain their conditions,
compositions and soil moisture.
7
1.5 Scope of the study
In this study, two different types of soil were collected which are peat and clay soil.
Peat samples were collected from Kampung Parit Nipah and Institute Peat Research
Station (IPRS), Pontian, while clay samples were collected from the Research Centre
of Soft Soil (RECESS), UTHM. This study is also focused on the sampling method of
undisturbed sample especially for soft soil due to no proper method of collecting
samples. Clay soil was conducted to compare with peat soil based on a standard
method. It is also focused on behaviour of soft soil such as peat and clay soil. By
establishing the engineering properties of soft soil; it involves field and laboratory
testing.
For the laboratory test, it is significant in measuring the physical test like
measuring shrinkage characteristics for different types of soil, diameter of samples,
different grain sizes, temperature and duration of testing. A physical test also includes
Particle Size Distribution, Degree of Decomposition, Specific Gravity, Moisture
Content, Loss of Ignition, Liquid Limit, Fibre Content, Organic Content and pH test.
All tests were conducted according to BS1377:1990 and ASTM: D4427.
Shrinkage effect was evaluated by different techniques then the samples were
compared with a standard method with three different diameter sample sizes (50mm,
70mm and 100mm). For sample preparations, reconstituted sample was prepared by
using wet and dry sieve methods with two different grain sizes (0.300mm and
0.425mm). Meanwhile, undisturbed sample was prepared directly by using a PVC tube
that had been collected from field sites. Reconstituted and undisturbed samples were
placed into oven-dried with three different temperatures, which are air-dried, 60C and
105C to observe the shrinkage effect. Two different types of sample which are peat
and clay were used in order to establish and review the shrinkage behaviour of peat
soils to be compared with inorganic soil.
8
1.6 Outline of the thesis
An outline of the thesis during this study is listed as below:
Table 1.1: Outline of the study
Chapter Titles Description
01 Introduction
The background of this study, including the
objectives of the project, aims, scopes of study and
problem statement.
02
Literature
review of past
research
Critical reviews from the past researches that
related to this study, which include soil
properties/characteristics (peat soil), laboratory
testing techniques and theories and shrinkage
characteristics.
03 Research
Methodology
Materials and experimental works in terms of
sample preparation, site investigation, test
equipment and procedure of the laboratory and field
testing. This section discusses on laboratory and
field testing techniques. It also proposes a modified
method of observation on shrinkage measurement
with different methods.
04 Results and
analysis
This chapter presents the test results include the
analysation of volume changes, loss of water and
linear shrinkage of soil with different techniques
that are reconstituted sample and undisturbed soil in
terms of swelling and shrinkage properties. It also
conducts basic properties. Correlations between the
various parameters are established and compared
with results from previous researchers.
9
05 Conclusion and
recommendation
Summary of study and detail recommendation for
future work based on current research experience
and literature review. It helps to establish a
modified method for further practice and long term
applications.
Reference A complete list of references is included
Appendices Appendices on relevant topics can be found at the
end of the thesis.
10
CHAPTER 2
LITERATURE REVIEW
2.1 Peat
2.1.1 Peat in Malaysia
Peat is found in all parts of the world except in deserts and the arctic regions which are
estimated to have about 1 billion acres of peat land in the world or about 4.5% of total
land areas (Deboucha et al., 2008). Distribution of peat soil is predominantly in a
tropical area. Meanwhile, Huat et al. (2011) reviewed that peat area consists of 300
million hectares and 2/3 of South East Asia. As in Indonesia, it is covered by 26 million
hectares, then, for Japan, the peat area consists of approximately 2000 km2, 170 million
hectares of peat in Canada, 150 million hectares of peat soil in Rusia and U.S. consists
of 30 million hectares of peat. He concluded that Canada has the largest area of peat
in the world.
Peat has also been identified as one of the major types of soil that found in
Malaysia. According to Zainorabidin and Bakar (2003), almost 13% or 16,500 km2 of
areas in Sarawak is covered by peat and it is the most extensive peat lands in Malaysia.
90% of the area has more than 1 m thickness of peat. They also mentioned that in
Peninsular Malaysia, peat soils are found in the coastal areas, especially in the west
area which are Pontian, Batu Pahat, Kuantan and Pekan districts, West Selangor and
Perak.
Hashim and Islam (2008) tabulated the distribution of peat land and organic
soil in Malaysia as in Table 2.1 and Figure 2.1. It is stated that Sarawak has the largest
area covered by peat in Malaysia.
11
Table 2.1: The distribution of peat land and organic soil in Malaysia (Hashim and
Islam, 2008)
State Peat (ha) Organic Clay
Johor 228, 960 69, 540
Negeri Sembilan 6, 300 -
Selangor 194, 300 -
Perak 107, 500 -
Pahang 219, 561 62, 939
Terengganu 81, 245 6, 755
Kelantan 7, 400 -
Sarawak 1, 657, 600 -
Sabah 86, 000 -
Total for Malaysia 2, 588, 866 139, 234
Figure 2.1: Peat land distribution in Semenanjung Malaysia (642,857 ha) (Hashim
and Islam, 2008)
12
Generally, most of the peat areas have a problem with road construction and
foundation. The development process will be more difficult to be carried out because
of the nature of soft soil, loam, high organic content and a very low shear force because
it consists of fibre. These unfavourable characteristics of peat soil deposits make them
unsuitable for supporting most engineering projects or infrastructure development.
Furthermore, such ground presents failure due to ground instability such as localised
sinking and extreme settlement over extended time periods when subjected to an
increment in loading (Jarret, 1995; Huat et al., 2004). Most of the areas that
predominantly covered by peat cannot be developed by any infrastructure and most of
the buildings have lower than four-storey.
2.1.2 Properties of Peat soil
There are differences between organic soil, inorganic soils, and peat soil. For
soil that contains less than 20% of organic matter can be classified as inorganic soil.
Meanwhile soil that contains organic matter more than 20% can be considered as
organic soil and soft soil. As peat, it must have more than 65% of organic matter. Peat
soil is also known to have high content of fibre and mineral which is less than 35%.
Composition of peat for every location is different due to its origin fibre, climate,
humidity, water level and temperature. Huat et al. (2004) discussed that properties of
peat are divided into three which are physical, chemical and physico-chemical
properties. The physical structure changes in chemical state that is loss of organic
matter either in gas or solution by involving the decomposition and humidification of
soil.
Peat is divided into three groups of layers which are fibric, hemic and sapric.
Fibric is the peat soil with least decomposition with 67% of fibre content. Meanwhile,
hemic is known as semifibrous with a moderate decomposed plant which consist of
33% to 66% of fibre content and sapric with less than 33% of fibre content can be
called as sapric [Duraisamy et al. (2008); Huat et al. (2011); Tang et al. (2011)]. Peat
profile can be categorized into three distinguish degrees of decomposition which are
sapric, hemic and fibric. In general, sapric layer is located in the upper layer underlain
by hemic and fibric.
13
In Malaysia, classification of peat and organic soils is based on the British
Standard 5930:1981. However, this classification has been modified and improved by
Public Work Malaysia to make this system works better with the Malaysia
environment (Jarret, 1995). Table 2.2 presents the properties of peat soils and the Von
Post Scale of Humidification (Ekono, 1981) is shown in Table 2.3.
Table 2.2: Properties of peat soil based on types of peat
Properties Fibric peat Hemic peat Sapric peat
Bulk density (γb) 1.260 Mg/m3 1.170 Mg/m3 0.996 – 1.019
Mg/m3
Dry density (γd) - 0.180 Mg/m3 0.243 Mg/m3
Moisture content (w) 630 – 670% 791 % 140 – 300%
Void ration (e) 8.36 10.48 – 15.98 4.12 – 4.84
Fibre content 90.00% 65% 31 – 32%
Specific gravity (Gs) 1.24-1.64 1.88 1.49 – 1.56
Classification/Von Post H3 H4 H8
Linear Shrinkage 12% 7 – 29% -
Liquid Limit 380% 119% 240 – 330%
pH 3 – 4 3.6 -
Loss on ignition 97 – 99% 78.76% 70 – 80%
Location Pontian Parit Nipah West Malaysia
References Tang (2011) Atemin (2012)
Huat et al.
(2004);
Duraisamy
(2007)
14
Table 2.3: The Von Post Scale of Humidification (Ekono, 1981)
Symbol Description
H1
Completely undecomposed peat which, when squeezed, releases
almost clear water. Plant remains easily identifiable. No amorphous
material presents.
H2
Almost entirely undecomposed peat which, when squeezed, releases
clear or yellowish water. Plant remains easily identifiable. No
amorphous material presents.
H3
Very slightly decomposed peat which, when squeezed, releases
muddy brown water, but no peat passes between the fingers. Plant
remains identifiable and no amorphous material presents.
H4
Slightly decomposed peat which, when squeezed, releases very
muddy dark water. No peat is passed between the fingers but the plant
remains slightly pasty and lost some of its identifiable features.
H5
Moderately decomposed peat which, when squeezed, releases very
“muddy” water with a very small amount of amorphous granular peat
escaping between the fingers. The structure of the plant remains quite
indistinct although it is still possible to recognize certain features.
The residue is very pasty.
H6
Moderately highly decomposed peat with a very indistict plant
structure. When squeezed, about one-third of the peat escapes
between the fingers. The residue is very pasty but shows the plant
structure more distinctly than before squeezing.
H7
Highly decomposed peat. Contains a lot of amorphous material with
very faintly recognizable plant structure. When squeezed, about one-
half of the peat escapes between the fingers. The water, if any is
released, is very dark and almost pasty.
H8
Very highly decomposed peat with a large quantity of amorphous
materials and has a very indistinct plant structure. When squeezed,
about two-thirds of the peat escapes between the fingers. A small
quantity of pasty water may be released. The plant material remains
in hand and consists of residues such as roots and fibres that resist
decomposition.
H9
Practically fully decomposed peat in which there is hardly any
recognizable plant structure. When squeezed, it is a fairly uniform
paste.
H10 Completely decomposed peat with no discernible plant structure.
When squeezed, all the wet peats escape between the fingers.
B1 Dry peat
B2 Low moisture content
B3 Moderate moisture content
B4 High moisture content
B5 Very high moisture content
*Note: The moisture of each peat sample is estimated using the above scale of 1-5
and symbol “B” (derived from Swedish blӧthet = wetness)
15
By referring to the properties of In-situ peat soil that was obtained by Alwi
(2008), moisture content and fibre content have value in the range of 700 – 850 % and
84.99%. Peat soil is classified by conducting Von Post Scale of Humidification (source
Ekono, 1981). It was shown that the soil is slightly decomposed peat which, when
squeezes, it releases very muddy dark water. Moreover, no peat is passed between the
fingers but the plant remains slightly pasty and lost some of its identifiable features.
Soil sample is classified as H4.
Basic parameters such as water content, fibre content, organic content, specific
gravity and linear shrinkage are included in this study as shown in Table 2.4. One of
basic parameters is water content. The values depend on its origin, degree of
decomposition and chemical composition of peat. Naturally, peat has very high natural
water content due to its natural water-holding capacity (Huat et al., 2011). The water
content is in the range between 414 to 850%. Past researchers conducted water content
testing according to BS 1377: Part 1: 1990 which requirements for oven-drying
method.
Specific gravity of peat is greatly affected by its composition and percentage
of the inorganic component. It is related to the degree of decomposition and mineral
content of peat. Higher specific gravity indicates higher degree of decomposition and
higher mineral content. The determination of the specific gravity of the peat soil
sample uses small pycnometer method according to BS 1377: Part 2: 1990. Specific
gravity lies in the range from 0.9 to 1.88.
Organic matter influences many of the physical, chemical and biological
properties of soils. Some of the properties are influenced by organic matter including
soil structure, soil compressibility and shear strength. According to BS 1377: Part 3:
1990, the organic content will determine the mass loss on ignition.
As mentioned previously, there are differences between organic soil, inorganic
soils, and peat soil. For soil that contains less than 20% of organic matter can be
classified as inorganic soil while soil that contains organic matter more than 20% can
be considered as organic soil and soft soil. As peat, it must have more than 65% of
organic matter. Table 2.4 shows that organic content that is valued between 78.76 to
99% while fibre content is from 58 to 90%, which is in the range to classify the soil as
peat soil.
16
Table 2.4: Properties of peat soil of some areas in Malaysia
Location Klang, Selangor Matang,
Sarawak
Pontian,
Johor
Parit Nipah,
Batu Pahat
Water Content (%) 414 – 850 700 – 850 600 791 630-670
Fibre Content (%) 85 – 90 84.99 79 58 -
Organic Content
(%) 89 – 98 98.46 91 78.76 97 – 99
Specific Gravity 0.9 – 1.4 1.343 1.2 1.88 1.24 – 1.64
Linear Shrinkage
(%) 5.6 5.58 5 7 to 29 12
References Wong et
al. (2008)
Deboucha
and
Hashim
(2009)
Kolay et
al. (2011)
Atemin,
H.H.
(2012)
Tang, B.L.
(2011)
2.2 Clay soil in Malaysia
According to Guggenheim and Martin (1995), clay can be defined as a combination of
one or more clay minerals with traces of metal oxides and organic matter. Brand and
Brenner (1981) claimed that clayey soil has a compression strength between 25kPa to
50kPa. Clay is a natural substance which is called as a fine-grained soil that has
plasticity behaviour when mixed with water. Clay can be distinguished from other
fine-grained soils by the differences in size and mineralogy and it is formed by
sedimentary deposition process. Table 2.5 shows the classification of clay soil in
Malaysia (Balasubramaniam et al., 1985).
17
Table 2.5: Classification of clay soil in Malaysia (Balasubramaniam et al, 1985)
Types of soil Thickness (m) Colour Description
1 2-6 Light grey/ light
brown
Sand black with sea shells/ upper
layer
2 10-32 Greenish grey /
greyish
Loose sand at 2-3 m layer thickness,
multiple amount of shells and
organic materials
3 3-11 Light brown/
greyish brown Fine grained soil
4 4-25 Light grey/
yellowish grey
Non homogenous, with moderately
hard clay soil layer
5 - Light brown/ grey Peat soil group to sandy gravel soil
It also can be distinguished from other soils by Geotechnical testing based on
plasticity index of the soil on conducting the Atterberg Limits since clayey soil can
expand and shrink due to moisture content. By referring to the ASTM standard, clay
particles are smaller than 2 μm. Clay is also considered as the earliest to be used in
building materials. For a thousand years, it has the high qualities in this natural
product.
In Peninsular Malaysia, clayey soil is commonly found in coastal areas of the
east and west Malaysia, especially in the coastal areas of Johor, Melaka, Selangor and
several areas in East Malaysia which are Kelantan and Terengganu (Abdullah and
Chandra, 1987). The thickness of the clayey soil layer in those locations is
approximately at 35 meters. Abdullah and Chandra (1987) found the thickness of the
clay soil in Peninsular Malaysia as shown in Table 2.6.
Table 2.6: Thickness of clay soil in Peninsular Malaysia (Abdullah and Chandra,
1987)
Location Thickness (m)
Perlis and Kedah 5-12
Sungai Kedah river dam 8-12
Alor Setar airport 12
Prai and Penang Bridge 12-25
Butterworth – Changkat Jering highway 5-15
Sungai Kerian basins 10
Bagan Datoh – Teluk Intan 5-11
Klang port 8-30
18
Kg. Acheh – Marine Harbour 3-7
Development project area in agricultural at Johor
Bahru 10-35
Kuantan 3-20
Sungai Kuantan bridge 5-12
Kuantan Port 3-15
Chukai 4-8
Semerak – Kemasin 3-10
Ting and Ooi (1977) conducted engineering characteristics of clay and found
that the sensitivity of clayey soil is a moderate sensitivity and a little loam. Table 2.7
below shows some characteristics of clay soil classification in Peninsular Malaysia by
Tajuddin (2004).
Chen and Tan (2003) studied properties of clay in Klang area, they found that
the thickness of the soil may vary from 20 to 40m. The liquid limit of this soil is high
which mostly about 50 to 150%. Plasticity index varies from 20 to 80% and the
compression ratio is in the range of 0.25 to 0.5. It is shown that there is a relationship
between the compression index and moisture content.
19
Table 2.7: Characteristics of clay soil classification in Peninsular Malaysia (Tajuddin, 2004)
Source Characteristics of clay classification
West Coast Moisture
Content (%)
Unit Weight
(kN/m3)
Specific
Gravity, Gs
Particle Size
Distribution (%) Activity
Liquid Limit
(%)
Plastic Limit
(%)
Liquidity
Index
Ting & Ooi
(1977) 20 - 140 - -
33-65 clay
24-62 silt
1-36 sand
- 40-155 10-45 -
Abdullah &
Chandra
(1987)
20-175 14.6-15 2.53-2.6
15-55 clay
38-70 silt
7-16 sand
Natural -
Active - - 0.5-1.2
Malaysian
Highway
Authority
(1989)
20-120 14-17 -
30-70 clay
25-55 silt
1-30 sand
- 40-100 20-40 0.4-2.3
Kobayashi, et
al. (1990) 40-125 14.5-17.5 2.45-2.7
25-85 clay
15-60 silt
0.45 sand
- 50-130 20-70 -
Aziz (1993) 15-130 14-15.5 2.6
27-59 clay
25-64 silt
2-28 sand
Non active –
active (0.77-4) 40-130 16-53 0.1-1.6
Ramli, et al.
(1994) 12-175 13-16.5 2.35-2.75
50-60 clay
40-50 silt
<5 sand
Natural –
Active (1.5-
1.8)
50-150 20-65 -
19
20
Hussein
(1995) 20-160 13-16 2.5-2.8
50-60 clay
20-40 silt
0-25 sand
Non active –
active (0.5-2) 40-125 10-40 0.1-2.1
East Coast Moisture
Content (%)
Unit Weight
(kN/m3)
Specific
Gravity, Gs
Particle Size
Distribution (%) Activity
Liquid Limit
(%)
Plastic Limit
(%)
Liquidity
Index
Abdullah &
Chandra
(1987)
21-107 16.3-17.1 2.5-2.57
31-56 clay
16-49 silt
6-28 sand
- - - -
Kobayashi et
al (1990) 70-100 14.5-15.5 2.65-2.7 - - - - -
Ramli et al
(1994) - - - -
Non active -
active (0.6-
1.2)
- - -
20
21
2.3 Shrinkage Characteristics
2.3.1 Definition of Shrinkage Measurement
The shrinkage limit (SL) is the water content where further loss of moisture will not
result in any more volume reduction (United States Army Corps of Engineers,
1970). The test to determine the shrinkage limit is ASTM International D4943. The
shrinkage limit is much less commonly used than the liquid and plastic limits.
Shrinkage limit of a soil is defined as soil where reduction in water content will
not cause a decrease in the volume of the soil mass, but an increase in water content
will cause an increase in the volume of soil mass (McGraw-Hill Dictionary, 2003).
Haines (1923) and Strik (1954) also defined soil shrinkage as the specific
volume change of soil relative to its water content and mainly due to clay swelling
properties. It can be measured in most soils with more than 10% of clay content
(Boivin et al., 2006). This process is reversible with changes in water content and the
reverse to shrinkage is swelling.
The Shrinkage Limit of a soil is defined as the water content at which no further
volume decrease occurs, but where the degree of saturation is still essentially 100 %
(Holtz and Kovacs, 1981) (Figure 2.2).
Figure 2.2: Definition of shrinkage limit of clay soil (Holtz and Kovacs, 1981)
22
In terms of linear shrinkage, it has been introduced by the Texas Highway
Department in 1932 (Heidema, 1957) and it is currently described as a standard test
procedure of bar linear shrinkage test in British Standard (1990). It was found to be
the most reliable soil constant in road construction (Netterberg, 1978) and most
significant indicator of cohesion for gravel wearing course material (Paige-Green,
1989). Haupt (1980) and Emery (1985) performed studies to determine subgrade
moisture prediction models and indicated that the bar linear shrinkage produced good
result than any other Atterberg Limit results. Paige-Green and Ventura (1999)
concluded that the bar linear shrinkage test is a more effective test to indicate material
performance than the traditional Atterberg limits.
Cerato and Lutenegger (2006) performed linear shrinkage test by conducting
liquid limit test with Casagrande cup. A third of the soil was placed in a greased brass
mould approximately 140 mm long and 25 mm in diameter. The soil was placed in the
mould in three layers and tapped against a flat surface in between the layering to
remove air bubbles from the soil. The sample was allowed to air dry for four hours.
Then the soil sample was placed in an oven at 105°C for 18 hours.
After the soil was dry, the mould was removed from the oven and allowed to
cool. The length of the soil sample was measured three times with digital callipers and
the average was used to calculate linear shrinkage using the equation:
𝐿𝑆 = (1 − 𝐿𝑎𝑣𝑔
𝐿𝑜) 𝑥 100 (2.1)
Where:
LS = Linear Shrinkage (%)
Lavg
= Average Length (mm)
Lo = Original Length of Brass mould (mm)
Cerato and Lutenegger (2006) mentioned that Linear Shrinkage test potentially has
a number of advantages over other tests, including:
1. The test is simple to perform
2. The test is essentially independent of operator and therefore may be subject to
less variability.
3. The equipment is simple and inexpensive.
4. The test does not require the use of toxic materials.
23
5. The test can be used for soils of low plasticity, such as silts, as well as for clays.
6. The test directly measures the desired behaviour; i.e., shrinkage.
There are two laboratory test methods of measuring the shrinkage properties of
fine-grained soil which are Shrinkage Limit (Head (1994) and Linear Shrinkage (BS-
1377:90). Shrinkage Limit test calculates the volumetric shrinkage while Linear
Shrinkage test is used to calculate one-dimensional shrinkage, although the volumetric
shrinkage may be calculated. The linear shrinkage is a measurement of the average
oven dry length of the sample after shrinkage of the original length, which occurs at
initial water content at or above the Liquid Limit.
2.3.2 Shrinkage Process
In a dry season, as the moisture content decreases, capillary stress in the void spaces
increases due to the increment of surface tension. This increased surface tension tends
to pull adjacent soil particles closer together, resulting in an overall soil volume to
decrease. As moisture content continues to decrease, capillary stress continues to
increase which continues to reduce overall volume. However, the shrunken soils will
tend to swell when access to water due to unusual rain (Pavement Interactive, 2008).
Soil shrinkage is generally confined to the upper portions of soil. Chegenizadeh
and Nikraz (2011) mentioned that it is caused by a reduction in soil moisture content
through (i) evaporation from the soil surface in dry climates, (ii) lowering of the
groundwater table and (iii) desiccation of soil by trees during the dry season in humid
climates as illustrated in Figure 2.3.
24
Figure 2.3: Shrinking Soils Mechanism
(http://www.pavementinteractive.org/article/shrinking-and-swelling-soils, 2008)
2.3.3 Shrinkage of Peat Soil
Waltham (2000) stated that the largest area of peat soils of Britain is located in the
fenlands along the East Midlands which is known as weak, highly compressible and
also high shrinkage when it is drained. The peat soil area will cause ground subsidence
even though without any loading due to a combination of consolidation and wastage.
The loss of water will allow the peat with porous particle, thereby it will increase the
density but reduce its volume. Holme Post peat area was drained to control the River
Ouse. They also realized that peat land area will be more useable and inhabitable when
it is drained but it will cause the ground surface to be subsided.
Figure 2.4 shows the record of ground subsidence in the peat soil area in the
Holme Post within 150 years. The subsidence of soil that had been observed over 150
years were related to the thickness of peat, water table and the ground surface which
is decreased compared to the original peat thickness which is 6.7 meters. In the first
50 years after its initial drainage (the water content of peat began to decrease), it shows
that its thickness of peat was subsided nearly 3.2 meters and it has lowered the water
table from its ground surface. Waltham (2000) observed that there was no subsidence
in the period 1890 to 1925 due to arable farmland replacement. It appeared with
smaller scale measurement of subsidence as it continued in 2000’s as the land absorbed
and lost water.