THE STUDY OF THE COMPRESSIBILITY CHARACTERISTICS OF
SOFT SOIL IN SARAWAK
WONG SEAK YEO
This project is submitted in partial of fulfilment of the requirements for the degree of Bachelor of Engineering with Honours (Civil Engineering)
Faculty of Engineering UNIVERSITI MALAYSIA SARAWAK 2005 UNIVERSITI MALAYSIA SARAWAK Kota Samarahan
fk BORANG PENGESAHAN TESIS
Judul: The Study of The Compressibility Characteristics of Soft Soil in Sarawak ______
Sesi Pengajian: 2001 - 2005
Saya WONG SEAK YEO______(HURUF BESAR)
mengaku membenarkan tesis * ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dengan syarat-syarat kegunaan seperti berikut:
1. Tesis adalah hamilik Universiti Malaysia Sarawak. 2. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Membuat pengdigitan untuk membangunkan Pengkalan Data Kandungan Tempatan. 4. Pusat Khidmat maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi pengajian tinggi. 5. ** Sila tandakan ( √ ) di kotak berkenaan
Sulit (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan 1 Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972)
Terhad (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/ 1 badan di mana penyelidikan dijalankan).
Tidak Terhad
______(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)
Alamat tetap: Lot.2806, Jalan Bunga Raya, 1 Pasir Pinji, 1 1 Dr. Prabir Kumar Kolay 31650 Ipoh, Perak. 1 (Nama Penyelia)
Tarikh: Tarikh:
CATATAN * Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah, Sarjana dan Sarjana Muda ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT dan TERHAD. PKS/2001 The Following Final Year Project Report:
Title : THE STUDY OF THE COMPRESSIBILITY
CHARACTERISTICS OF SOFT SOIL IN SARAWAK
Name of the author : WONG SEAK YEO
Matrix Number : 7477
Was read and certified by :
______
Dr. PRABIR KUMAR KOLAY Date
Project Supervisor ACKNOWLEDGEMENTS
My sincerest appreciation must be absolutely to my supportive and helpful supervisors; project supervisor, Dr. Prabir Kumar Kolay for his lofty visions, guidance, supports and valuables knowledge during the project work.
The author also take this opportunity to thank the laboratory assistants of Civil
Engineering Program, Faculty of Engineering, Universiti Malaysia Sarawak and the stuffs and laboratory assistants in Geospec for their supply of undisturbed soil samples and use their lab facilities and assistance in carrying out the laboratory works during the progression of the project.
A special thanks to my dearest friends Ong Chee Zen, Chong Kah Weng, Chai
Peng How, Kho Joo Tiong, Ong Khin Kiat, Adrian Fong Wei Yi, Dorothy Chai Sim
Yee, Onn Yin Wee and Ling Leh Shia who had been so helpful and supportive along the implementation of the project.
The author is very grateful to his family, especially Madam Lee Tng Chu and
Mr. Wong Kow Chye, who always give their full supports and love. Your advice and guidance will be always bear in mind.
Finally, I am deeply grateful to those individuals who involve directly and indirectly all throughout the process of doing this project.
i ABSTRACT
The present study investigates the compressibility characteristics of soft soil in Sarawak. To accomplish this study, eight undisturbed soil samples are collected from different location i.e., Desa Senadin (Miri), Kampung Punang
(Lawas), Lundu (Kuching), Dan (Mukah), Sungai Miri (Miri) and Upper Lanang
(Batang Rajang). Different laboratory tests (moisture content, Atterberg limit, specific gravity, grain size analysis, and consolidation) have been conducted on these soil samples. The results reveal that the value of co-efficient of volume change, mv for all the soil samples is gradually decreasing with the increase of higher-pressure ranges but the co-efficient of consolidation, cv for all the samples tested do not follow any specific trend with the increase of pressure. The compression index, Cc values calculated from e-log P graph and formula ( Cc =
0.009 × (wL-10) ) are correlated with the values of plasticity index (PI).
ii ABSTRAK
Kajian ini mengkaji tentang ciri-ciri kemampatan tanah lembut di Sarawak. Untuk menyempurnakan kajian ini, lapan sample tanah telah dikumpul dari kawasan-kawasan yang berlainan, yakni Desa Senadin (Miri), Kampung Punang (Lawas), Lundu
(Kuching), Dan (Mukah), Sungai Miri (Miri) and Upper Lanang (Batang Rajang).
Kajian eksperimen yang berlainan tentang moisture content, Atterberg limit, specific gravity, grain size analysis, dan consolidation telah dijalankan terhadap smple-smple tanah itu. Keputusan menunjukkan bahawa pemalar bagi perubahan isipadu, mv untk semua sample tanah adalah berkadar songsang dengan tekanan. Tetapi, pemalar bagi consolidation, cv untuk semua tanah yang dikaji tidak mempunyai sebarang trend yang unik dengan peningkatan tekanan. Tambahan pula, index mampatan, Cc yang dikira daripada graf e-log P dan dikira dengan menggunakan formula (Cc = 0.009 × (wL-10)) saling dihubungkan dengan nilai index plastik (PI).
iii Table of Content
CONTENTS Page No.
ACKNOWLEDGEMENTS i
ABSTRACT ii
ABSTRAK iii
TABLE OF CONTENTS iv
LIST OF TABLES vii
LIST OF FIGURES viii
LIST OF SYMBOLS ix
CHAPTER 1-INTRODUCTION
1.1 General 1
1.2 Physical Properties and Classification 2
of Soft soil
1.3 Construction on Soft soil 4
1.4 Statement of the Problem 6
1.5 Objectives of the Present Study 7
1.6 Organization of the Project Paper 8
iv CHAPTER 2-LITERATUREVIEW
2.1 General 9
2.2 Physical Properties of Soft Soils 9
2.2.1 Organic content 10
2.2.2 Water content 11
2.2.3 Specific gravity 13
2.3 One-Dimensional Compression 15
2.3.1 Effect of permeability on consolidation 16
2.3.2 Compression - time relation 17
2.3.3 Estimation of final settlement 22
2.4 Critical appraisal 23
CHAPTER 3-MATERIALS, TEST PROGRAMME AND PROCEDURE
3.1 General 25
3.2 Test Materials 25
3.3 Test Programmes 26
3.4 Test Procedure 27
3.4.1 Moisture content 28
.4.2 Liquid limit and plastic limit 28
3.4.3 Specific gravity 29
3.4.4 Grain size analysis 30
3.4.5 Void ratio, e 31
3.4.6 Consolidation test 31
v CHAPTER 4-RESULTS AND DISCUSSION
4.1 General 33
4.2 Moisture content 33
4.3 Grain size distribution 34
4.4 Atterberg limit 37
4.5 Specific gravity 37
4.6 Compressibility characteristics 38
4.7 Consolidation settlement 44
CHAPTER 5-CONCLUSION AND RECOMMENDATION
5.1 General 46
5.2 Recommendation 47
REFERENCES 49
APPENDIX
vi LIST OF FIGURE
Page No.
Fig. 2.1 Correlation of water content with loss-on-ignition 13
Fig. 2.2 Correlation of specific gravity with loss-of-ignition 15
Fig, 2.3 Distortion of settlement curve by resetting of time zero 18
Fig.2.4 Middleton Wisconsin peat; Settlement --Time 20
curves on various scale
Fig. 2.5 Middleton Wisconsin peat, oedometer test #6, 21
isotaches for loading and reloading
4 Fig. 2.6 Polder Zegveld peat, w/N - log σv’ for 10 d loading 23
Fig. 4.1 Grain size distribution graph for different clay soil 34
samples
Fig. 4.2 Square root of time method 39
Fig.4.3 e-log P graph for Sample-1 39
Fig. 4.4 mv values of various sample with different pressures 42
Fig. 4.5 cv values of various sample with different pressures 42
Fig. 4.6 Relation between compression index and plasticity index 43
viii LIST OF TABLE
Page No.
Table 3.1 Test programmes 27
Table 4.1 Physical (index) properties of samples 36
Table 4.2 Consistency limits for different soil samples 37
Table 4.3 Specific gravity of different soil samples 38
2 Table 4.4 mv values (in m /kN) for different soil samples 41
with various pressure ranges
Table 4.5 cv values for different soil samples with various 41
pressure ranges
Table 4.6 Cc values for different soil samples 43
Table 4.7 Settlement estimation by using Cc of sample 44
with 1m depth
Table 4.8 Settlement estimation by using mv of sample 45
with 1m depth
ix CHAPTER 1
INTRODUCTION
1.1 General
Normally clay, peat and organic soils considered as soft soil. They show a wide range in the degree of compressibility. In Sarawak, the peat and soft soil creates an acute problem for any type of construction (building and road). The formation of peat soil is a relatively short biochemical process carried on under the influence of aerobic micro-organisms. Peat materials can be characterized for geotechnical engineering purposes in various ways depending on the purpose for which they are being described. The most relevant physical characteristics are water content, bulk density, organic content, and exchangeable cation; whereas engineering properties include compressibility, swelling and shrinkage, shear strength (stability) and permeability.
1 Soft soil (e.g., clay, peat and organic soils) is generally a topic of interest by the engineering community. Geotechnical engineering challenges especially associated with embankment and road construction over soft soil (e.g., clay, peat and organic soils) include potential instability and excessive long-term settlement.
Although construction over such soils is generally avoided, the declining availability of sites with more favourable foundation soils has necessitated the development of area underlain by peaty or organic deposits. (O' Loughlin and
Lehane, 2002). However, with the recent advances in the use of soil reinforcement, construction has primarily become a problem of controlling settlement (Edil and Den Haan, 1994).
The resurging interest in soft soil as foundation materials have been underlain by the continual research and study on both the physical and engineering properties of such soils and the correlation among these properties.
The origin and formation of soil clay minerals, namely micas, vermiculites, smectites, chlorites and interlayered minerals, interstratified minerals and kaolin minerals, are broadly reviewed in the context of research over the past half century. It is concluded that these early overviews may still be regarded as being generally valid, although it may be that too much emphasis has been placed upon transformation mechanisms and not enough upon neoformation processes. (Wilson M.J., 1999)
2 1.2 Physical Properties and Classification of Soft soil
Soft soil, mainly peat, is encountered in tropical and low-lying areas where water table is near or above ground surface. They are present mostly in surface soils but in some cases as deep deposits. Soil organic matter originates from plant or animal remains and is often observed in various stages of decomposition with an end product known as humas. There are certain terms used in characterising physical characteristics of peat. Generally, the physical properties of organic soils are of particular relevance to densification purposes. Organic soil materials consist of four components', mineral material, organic material, water and air. The characterization of the physical properties of organic materials is made difficult by the changes in the proportions of the four components.
Traditionally the study of physical properties was more the domain of soil mechanics and soil engineering than of soil chemistry. The former express the characteristics of materials on a volume basis, whereas chemists commonly use weight ratios. There is a tendency at present to use volume ratios, because it is more practical to work with. Because of the strong interdependence of the various physical properties, it is difficult to discuss each individual characteristic independently. It is thus necessary to make frequent cross-reference. The important geotechnical terms are water content, fibre content, degree of humification and ash content, organic content etc.
3 Organic soils, which according to definition contain a varying proportion of organic matter, include peat (remains of dead vegetation in various stages of decomposition), gyttja (plant and animal remains deposited in lakes) as well as organic silts and organic clays. The types of soil differ greatly from each other with respect to engineering properties.
Classification of peat is a controversial issue with numerous approaches available for varying purposes. Peat is a naturally occurring highly organic substance derived primarily from fossilized plant materials. Peat is distinguished from organic soils by its high organic content (>75%), lower decomposition or humification, and fibre content. It also refers to a distinct mode of behaviour different than traditional soil mechanics in certain aspects. A possible approach is being considered by the American Society for Testing and Materials (ASTM) for classifying peat soil.
If a soil has less than 5% of organic content, its behaviour is hardly affected by the organic content, and as such it is termed as inorganic soil. The organic content of 6 to 20% has effects on the properties of whole soil mass but still its behaviour is very much like that of inorganic soil. Usually this type of soil is termed as either organic silt or organic clay. When the organic content of a soil is in between 21 to 74% percent, the organic matters govern the properties.
Traditional soil mechanics may not be applicable to these types of soils. They are generally silty or clayey organic soils. Most importantly, if the organic content of
4 a soil is more than 75%, it is considered as peat. Peat soil displays behaviour distinct from traditional soil mechanics especially at low stresses. (Edil, 1994).
According to Tan the proposed site at Klang, Selangor, Peninsula
Malaysia (Fig. 1.1) is located at the contact boundary of Quarternary Alluvium and Kenny Hill Formation as shown in Fig. 1.1. The alluvial deposits are overlying the Kenny Hill Formation of weathered metasedimentary rock type. The alluvial deposits generally consist of very soft to firm silty Clay up to a depth of
25m to 30m with presence of intermediate sandy layers. Beneath the silty Clay stratum generally consists of silty Sand. Residual soils (Grade VI) and completely weathered materials (Grade V) derived from the weathering of Quartzite were only encountered at about 40m deep. The presence of quartzite rock-type was further confirmed from the observation of rock outcrop located about 2km from the site. The behaviour of soft alluvial soils is influenced by the source of the parent material, depositional processes, erosion, redeposition, consolidation and fluctuations in groundwater levels. Alluvial soils in Klang area usually show pronounced stratification and sometimes organic matter, seashell and decayed wood are present in this deposits.
5
Fig. 1.1 : Location of the Site.
Fig.1.2 : Geological Map of the Site.
The compressibility and permeability relationships of very soft clay is determined by a finite strain consolidation test with a constant surcharge which uses Gamma-rays and pore pressure transducers to measure density and pore pressure profiles, respectively, at various times of the test without hindering the consolidation process. The constant surcharge applied accentuates the changes in density and pore pressure profiles enabling them to be measured reliably.
6 These profiles are then used to determine the compressibility and permeability of the soft clay. A test is carried out to extract these properties, which are used in a finite strain consolidation theory to predict the settlement, void ratio, and pore-pressure distributions of other tests done under different initial and boundary conditions. The predictions are found to agree well with the experimental data, thus suggesting that the properties determined are accurate
(Tan, 1988).
1.3 Construction on Soft soil
Peat soils have certain characteristics that set them apart from most mineral soils and require special considerations for construction over them. These characteristics include: high natural moisture content (up to 1500%), high compressibility, low strength in natural conditions (typically Cu = 5 to 20 kPa), high initial permeability, high degree of spatial variability and potential for further decomposition. Edil (1994) reports a variety of construction methods that have been developed and used to allow construction of structures and embankments over soft soil (e.g., clay, peat and organic soils). These methods include; avoidance, excavation- displacement/replacement, stage construction and preloading, thermal pre-compression, deep in-situ mixing, stone columns, piles and so on.
7 Sarawak has the largest peat area in Malaysia with 16500 m2 that makes up 13% of the state, of which 90% is more than 1 m in depth, Singh (1997).
Geographically, these peats are found in the administrative divisions of Kuching,
Kota Samarahan, Sri Aman, Sibu, Sarikei, Bintulu, Miri and Limbang on their coastal side.
Ling (1997) conducted a research on stress-void ratio relationship of peat soil and concluded that the conventional formula cannot be applied for computation of fill ground in peat area. He proposed a new formula; however, he was not optimistic of using the formula for calculating settlement without having rigorous further study. Yogorajah and Ganeshan (1997) worked on application of ground improvement techniques in soft soil deposits. Of the available methods they highlighted the common methods of vertical drains with surcharge and the soil reinforcement by traditional method of locally available material bamboo and geotextile. They claimed that the traditional method appeared to be economical.
Mc Manus et al. (1997) reported their experience with the peat soil of Sarawak and their recommendations were similar to that of Yogorajah and Ganeshan
(1997), especially with the peat deposit within a depth range of 3 m to 10 m.
According to Ling (1997), the construction of the Sungai Sarawak Barrage involves major geotechnical works in soft clay. These include deep excavation with well pumping for ground water control, pile installation, embankment preloading and rockfill construction of causeways.
8
1.4 Statement of the Problem
The construction on and with soft soil has never been apprehended as simple job owing to non-availability of established analytical methods and construction techniques for a specific site. Several methods of soil improvements are available (Yogorajah and Ganeshan, 1997). Though a significant volume of research work has been done on the various aspects of peat soil, yet it appears that the estimation of settlement still needs further study. Understandably, its use in practice is so important. The most severe problem associated with peat soil is that the sample decomposes with time and the properties are getting changed. Thus in the present study was aimed at investigating the feasibility of using simple tests like determination of water content, Atterbergs limit and compressibility characteristics (i.e., co-efficient of volume change, compression index, co- efficient of consolidation etc.) of various soil samples collected from different location in Sarawak and to correlate these properties to estimate the settlement in a simple manner.
There are always two main problems in soft clay, namely stability and settlement. However, many practising engineers always forget about the importance of settlement problem. Therefore, more effort should be emphasized in the process of interpretating soil parameters for settlement analysis (Tan).
9 Soil samples from several selected locations (i.e., Desa Senadin,
Kampung Punang, Lundu, Mukah, Sungai Miri and Upper Lanang) have been collected and tested for water content-, grain size distribution, specific gravity,
Atterbergs limit indices and consolidation properties. Laboratory tests are to be done and the data be analyzed to find correlations among the properties mentioned. The findings may be used in any fill projects by performing simple tests, avoiding complicated and expensive ones, like water content and plasticity index to estimate the settlement of a fill.
1.5 Objectives of the Present Study
The present study is aimed at investigating some physical and engineering properties of soil samples collected from various locations in Sarawak. The main objectives of the present study are as follows:
(i) To review the available related literature in order to have an
in depth view of the subject.
(ii) To investigate the correlation between water (moisture)
content and the compressibility characteristics mainly
compression index (Cc) of soft soil.
(iii) To investigate the correlation between Atterbergs limits and
the compressibility characteristics of soft soil.
10 1.6 Organization of the Project
This outcome of this investigation is presented in a volume of five chapters. First chapter is essentially an introduction to the topic and the intended work. The second chapter includes the review of related literatures. Chapter three covers test programme, procedure and testing materials. Chapter four comprises of the experimental results and discussion. To summaries the work, chapter five presents the conclusion of the study and suggests the recommendations for future research.
11 CHAPTER 2
LITERATURE REVIEW
2.1 General
The present study aims at finding out a relationship between moisture content and compressibility characteristics of soft soil (e.g., clay, peat and organic soils). In this chapter the available literature on inter-relation between composition and compressibility of mainly peat, organic soil and clay soil have been presented.
2.2 Physical Properties of Soft Soils
The concepts of behavior of inorganic clays have often been applied to peat and organic soils, with varying degrees of success. It is possible to apply traditional soil mechanics theory to these soils with special attention and consideration by
9 limitations of methods of characterization owing to anomalies in behavior of peat and organic soils (den Haan, 1997). The main physical properties of peat and organic soils are being water content, loss on ignition, organic content and specific gravity. The engineering properties and thus the foundation behavior are greatly influenced by these properties.
2.2.1 Organic content
Extensive research has been carried out on the determination of the organic content of peat. However consensus has not been reached, neither the methods used nor details of any method. Sometimes, various methods are recommended for different purposes such as calorific potential or identification of clays etc.
(Andrejko et al., 1983).
Numbers of wet ashing techniques involving chemical analysis are available for the determination of organic content, but such methods are generally successful in soils with relatively small amounts of organic matter
(Hobbs, 1986). A more common and effective method is to burn a small soil specimen in a furnace after drying at 105°C for 24 hours. The difference between masses before and after burning gives the ash content or loss-on-ignition (N).
The organic content can then be determined by the following expression:
10