DETERMINATION OF BASIC SOIL PROPERTIES AND SHEAR STRENGTH OF PEKAN SOFT CLAY MOHD FARUQ BIN SA ADON A report submitted in partial fulfillment of the requirements for the award of the degree of achieving Bachelor of Civil Engineering Faculty of Civil & Earth Resources Universiti Malaysia Pahang NOVEMBER 2009
ABSTRACT Soft clay soil can be categorized as problematic soil. The low strength and high compressibility characteristics the soil had, are the major reasons why a careful design analysis could be taken for any structure built on it. Due to these problems, soil investigation on the basic properties and shear strength of the soil must be carried out. This soft clay study has contributed to local engineering studies regarding the basic soil properties and shear strength in Langgar and Pahang Tua soil, where both are located in Pekan. Attempts were made to analyze the soil samples in laboratory. Overall, from the basic soil properties results, there are strong potential for the soil in Langgar and Pahang Tua to be concluded as soft clay type of soil. From the requirement set by American Association of State Highway and Transportation Officials (AASTHO), both Langgar and Pahang Tua soil samples have been dominant by clay particles with more than 35% passing the No.200 sieve, which are 52% in Langgar and 57% in Pahang Tua. The natural moisture content in Langgar and Pahang Tua soil samples are each 57% and 48% which are within the range of moisture content for soft clay soil. For atterberg limit results, Langgar has liquid limit of 51% and plastic limit of 26%. For Pahang Tua, the liquid limit and plastic limit result are 58% and 27%. Based on plasticity chart, both Langgar and Pahang Tua have been determined to be plotted as clay with high plasticity. The shear strength test results have clearly shown the weakness of Langgar and Pahang Tua soil which are within the strength of a soft clay. Both Langgar and Pahang Tua have 19.18kPa and 21.11kPa of shear strength. The results that have been determined from this study can give an extra dimension and usage for engineers to use for any preliminary design in the area of Pekan. The results data of the basic soil properties and shear strength could also allow a quick and economic alternative in order to design for construction on soft clay soil.
ABSTRAK Tanah liat lembut boleh dikategorikan sebagai tanah yang bermasalah. Kekuatan tanah yang rendah dan ketinggian daya tekanan yang dikenakan menjadi antara faktor utama mengapa ketelitian sesuatu rekabentuk perlu dibuat jika struktur dibina di atasnya. Disebabkan masalah ini, kajian ke atas tanah terhadap ciri asas tanah dan kekuatan rich tanah perlu dilakukan. Projek ini telah menyumbang kepada analisis kejuruteraan ciri asas tanah dan kekuatan rich tanah di kawasan Langgar dan Pahang Tua, yang terletak di daerah Pekan. Banyak percubaan telah dilakukan untuk mengkaji contoh tanah di makmal. Secara keseluruhannya, daripada keputusan ujian terhadap ciri asas tanah di kedua-dua tempat, terdapat besar kemungkinan tanah berikut boleh dikategorikan sebagai tanah liat lembut. Daripada spesifikasi yang ditetapkan oleh American Association of State Highway and Transportation Officials (AASTHO), tanah di kedua-dua Langgar dan Pahang Tua telah didominasi oleh tanah liat dengan lebih 35% melepasi ayakan No.200, di mana 52% di Langgar dan 57% di Pahang Tua. Kandungan lembapan semulajadi tanah di kedua-dua Langgar dan Pahang Tua adalah 57% dan 48% di mana bersesuaian dengan nilai bagi tanah liat lembut. Bagi keputusan Atterberg Limits, kawasan Langgar mempunyai had cecairan sebanyak 51% dan had plastik sebanyak 26%. Untuk Pahang Tua, had cecairan dan had plastiknya adalah 58% dan 27%. Berdasarkan carta keplastikan, kedua-dua Langgar dan Pahang Tua telah dikenalpasti sebagai tanah liat yang mempunyai tahap plastik yang tinggi. Ujian terhadap kekuatan ricih tanah menunjukkan kelemahan yang ketara terhadap kekuatan ricih tanah tersebut iaitu di dalam lingkungan bacaan kekuatan bagi tanah liat lembut. Keduadua Langgar dan Pahang Tua mempunyai nilai kekuatan ricih tanah serendah 19.18kPa dan 21.11kPa. Segala data dan keputusan yang diperoleh daripada ujian-ujian di dalam kajian ini
dapat digunakan sepenuhnya secara ekonomi oleh jurutera di luar bagi merekabentuk struktur bangunan di kawasan tertentu di Pekan terutamanya di atas tanah liat lembut. TABLE OF CONTENT CHAPTER PAGE TITLE DECLARATION DEDICATION ACKNOLEDGEMENT ABSTRACT ABSTRAK TABLE OF CONTENT LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS LIST OF APPENDICES і іі ііі іv v vі x xii xiv xv CHAPTER 1 INTRODUCTION 1.1 General 1 1.2 Objectives 3 1.3 Scope of Study 3 1.4 Importance of Study 4 1.5 Problem Statement 5
CHAPTER 2 LITERATURE REVIEW 2.1 Introduction 7 2.2 Classification of Soil 9 2.2.1 American Association of State Highway and 10 Transportation Officials Classification System 2.2.2 Unified Soil Classification System 11 2.3 Clay 12 2.4 Clay Mineral and Formation 14 2.5 Soft Clay Properties 15 2.6 Depositional Area of Soft Clay 16 2.6.1 Fluvial Environment 17 2.6.2 Deltaic Environment 17 2.6.3 Bay and Lagoon Environment 18 2.7 Particle Size Distribution 18 2.7.1 Sieve Analysis 19 2.7.2 Hydrometer Analysis 20 2.8 Permeability of Clay 21 2.9 Sampling 22 2.10 Soil Consistency and Atterberg Limits 23 2.10.1 Liquid Limit 24 2.10.2 Plastic Limit 25 2.10.3 Shrinkage Limit 25 2.10.4 Plasticity Index 26 2.11 Natural Moisture Content 27 2.12 Soil Compaction 28 2.12.1 Unit Weight 28 2.13 Shear Strength 30 2.14 Shear Failure 31
2.15 Shear Strength Tests 33 2.15.1 Consolidated Drained Test 35 2.15.2 Consolidated Undrained Test 35 ` 2.15.3 Unconsolidated Undrained Test 36 2.16 Past Studies 37 CHAPTER 3 METHODOLOGY 3.1 Introduction 41 3.2 Objective Identification 42 3.3 Literature review 43 3.4 Sample Collection 43 3.5 Laboratory Test 44 3.5.1 Natural Moisture Content Test 45 ` 3.5.2 Particle Size Distribution Test 45 3.5.3 Atterberg Limits Test 46 3.5.4 Soil Compaction Test 48 3.5.5 Shear Strength Test 48 3.6 Data and Result Analysis 49 3.7 Discussion and Conclusion 49 CHAPTER 4 RESULTS AND DISCUSSION 4.1 Introduction 51 4.2 Particles Size Analysis 52 4.3 Soil Index Properties 55 4.3.1 Natural Moisture Content 55 4.3.2 Atterberg Limits 57 4.4 Dry Unit Weight 60
4.5 Shear Strength 63 4.6 Summary of Results 70 CHAPTER 5 CONCLUSION 5.1 Conclusion 71 REFFERENCES 75 APPENDIX A-B 77-109
LIST OF TABLES TABLE NO. TITLE PAGE 2.1 American Association of State Highway and Transportation 11 Officials (AASTHO) classification criteria 2.2 First and second letters of group symbols 12 2.3 Common properties of clay soil 16 2.4 U.S standard sieve number and openings 19 2.5 Typical values of coefficient permeability 21 2.6 Undrained shear strength of cohesive soil in accordance 31 from British Standard Code of Practice (CP) 2.7 Basic soil properties by past researchers 38 2.8 Basic soil properties by past researchers in 1.0m depth 39 2.9 Shear strength values of soil in Pekan 39 2.10 Shear strength values of soil in Johor 40 4.1 Particle size analysis in Langgar and Pahang Tua 54 4.2 Particle size analysis by Past Researchers 54 4.3 Average natural moisture content in Langgar and Pahang Tua 57 4.4 Natural moisture content by past researchers 57
4.5 Atterberg limits in Langgar and Pahang Tua 58 4.6 Atterberg limits results by past researchers 60 4.7 Maximum dry unit weight of soil samples in Langgar and Pahang Tua 63 4.8 Shear strength values in Langgar and Pahang Tua 64 4.9 Summary of soil properties in Langgar and Pahang Tua 70
LIST OF FIGURES FIGURE NO. TITLE PAGE 1.1 Study location in Pekan 4 2.1 Soft clay area in peninsular Malaysia 8 2.2 Soil classification based on grain size 10 2.3 Particle size distribution of soil in millimeter 13 2.4 Clay minerals; (a) Kaolinite, (b) Illite and (c) Montmorillonite 14 2.5 Atterberg limits state 24 2.6 Plasticity chart 27 2.7 Dry unit weight of various type of soils 29 2.8 Indication of how shear stress ( ) along the failure surface ( f ) 32 reaches the shear failure 2.9 Mohr s failure envelope and Mohr-Coulomb failure law 33 2.10 Mohr s circle and failure envelope for normally consolidated 34 clay 2.11 Total and effective stress failure envelopes for Consolidated 35 Undrained
2.12 Total stress Mohr s circle and failure envelope obtained from 36 Unconsolidated Undrained triaxial test 3.1 Flow chart of methodology 42 3.2 Sieve analysis instrument 46 3.3 Cone penetrometer for liquid limit test 47 3.4 Confining chamber used in shear strength test 48 4.1 Soil samples in Langgar and Pekan 53 4.2 Particle size distribution based on areas 55 4.3 Ranges of atterberg limits in Langgar and Pahang Tua 58 4.4 Relationship between plasticity index and liquid limit in Langgar and Pahang Tua 59 4.5 Dry unit weight of soil samples in Langgar 60 4.6 Dry unit weight of soil samples in Pahang Tua 61 4.7 Soil samples in Langgar 64 4.8 Visualization of mohr circles in Langgar 64 4.9 Result simulation of specimen one in Langgar 65 4.10 Result simulation of specimen two in Langgar 66 4.11 Soil samples in Pahang Tua 67 4.12 Visualization of mohr circles in Pahang Tua 67 4.13 Result simulation of specimen one in Pahang Tua 68 4.14 Result simulation of specimen two in Pahang Tua 68 4.15 Result simulation of specimen three in Pahang Tua 69
LIST OF SYMBOLS k - permeability w - unit weight of water - viscosity of water K - absolute permeability LL - liquid limit PL - plastic limit PI - plasticity index - shear strength c - effective stress cohesion intercept - effective stress angle of friction σ - effective stress - friction angle
LIST OF APPENDIXES APPENDIX TITLE PAGE A Sample Summary of Laboratory Testing for Langgar 77-91 B Sample Summary of Laboratory Testing for Pahang Tua 92-109
CHAPTER 1 INTRODUCTION 1.1 General Malaysia has become one of most developed country in this region. Developments throughout the industrialized sectors in this country have very much proven that technologies have helped to achieve the goal and mission to become a modern country. To become one of those countries, any developments should be done in proper ways. In civil engineering sector, procedures, planning and deep analysis should be taken in many situations before any development can be undergone. Civil engineering in Malaysia has developed rapidly ever since the First Malaysia Plan (RMK1) was established and declared in 1966. Up until now, where the Ninth Malaysia Plan (RMK9) was first introduced in 2006, Malaysia has become one of the fastest developed country in the region, if not in the world. Regarding of what the government has promised and planned for the country in the Seventh & Eight Malaysia Plan (RMK7 and RMK8), one of the major challenges are to establish the country with good growing business and structure developments. The developments have proved the plan are well organized by the government. These were the periods where award
winning airport; Kuala Lumpur International Airport (KLIA), one time tallest twin towers in the world; Kuala Lumpur City Centre (KLCC), Kuala Lumpur Tower, Light Rail Transit systems (LRT), and many more have seen Malaysia becoming respectively known from all over the world. Since Malaysia had achieved its independence in 1957, it took less than 50 years for the country to develop and create some modernization to its economy and structures development. However, to achieve level of developments that can be proud of are not as easy as people thought. Specifically, in civil engineering sector, engineers have seen many problems and analysis to deal with. Before any structures can be made, until the structures are perfectly made, there are many works to be considered in order to make the structures safe. Soil is the base of any structures as building will stand firm on it. Normally, a base must be strong, can resist failure and able to support huge load of a structure. This is why, before any constructions work can be done, analysis and study must be applied to the soil in order to know the status of the soil. The soil will give problems and difficulties to engineers as soil can present in many types, properties and strength. The variety of the soil is the factors that cause some soil to undergo excessive settlement, collapse, and have distinct lack of strength. Different types of soil could produce different soil characteristics as it is due to their nature of their pore fluids and their mineralogy of their fabric. This study presents the determination of basic properties and shear strength of soft clay in Pekan, Pahang. Any construction works which have been constructed in soft clay area are believed to face more problems compared to other types of soils. Soft clay soil is believed to experience more failure through its characteristics due to weak compressibility and problematic. Some of the significant problems happened to soft clay soil are its failure to supports huge loads as a foundation and its nature of high settlement.
1.2 Objectives a) To determine the basic soil properties of Pekan soft clay. b) To determine the shear strength of Pekan soft clay soil. 1.3 Scope of Study Pahang is known for its logistic location for marine activity and construction industry. By geological point of view, Pekan marine areas are believe to consist clay type of soil. Any development of industry in this marine area should be affected by the occurrence of the clay soil. That is why the investigation to the soil is more than necessary. In this case, two areas within the district area are chosen to be the investigation areas. Langgar and Pahang Tua are the two sites that are chosen to be the site location. From early physical observation through the soil, both areas are believed to be having clay-type of soil. The soil were soft in physical and greyly in colour. The site investigation data and analysis will be done and taken by the student as well as the sampling procedures. The soil sample will be tested in laboratory to obtain its basic engineering properties and shear strength. All the data will be used in order to obtain valuable information of the soft clay soil. Figure 1.1 below shows the study locations in Pekan.
Site 2 (Pahang Tua) Site 1 (Langgar) Figure 1.1: Study location in Pekan (malaysia-maps.com, 2006) 1.4 Importance of Study Soft clay is categorized into small or fine particles of soils. The emergence of development in this country has force the study of the soft clay to be done carefully as soft clay are happened to have less strength and always cause failure condition to
structure. In this country, the majority of soft clay are came from the marine type of soft clay. The fact that soft clay deposits are widespread and often cause problems to engineering design and structure, foundation failures in soft clay area are fairly common. That is why, to avoid unnecessary things from happened in the future, a very detail soil investigation need to be done and deep understanding by civil engineer towards soft clay soil are also important and crucial. The results from this study can also be used by engineers as important guideline while constructing structure in soft clay area. 1.5 Problem Statement Structures are meant to stand firm for many years to come and more importantly, could provide great strength to support loads within the structure. The unstable properties of soft clay are believed to be the major circumstances for any structure to be built on it. The major challenge of problems with soft clay soil are the stability of the soil and settlement. Engineering characteristics of soft clay soil should be studied into consideration as deep understanding of the analysis could help people in this field to understand how crucial and critical the soil could become to structures. In some areas in this country where soft clay are the major part of the soil, constructing structure on it could be complicated and design plan must carefully be made. All soils are compressible and could undergo volume changes when they are subjected to changes in the stress applied to them. Foundation settlements are the most emergence problems happened in building constructions. Many commercial and residential buildings have become distressed due to settlement. This problem is often caused by weak or improperly compacted soils. All buildings which are built on soft soil
are compatible to be constructed with weak foundation and having a high risk for structure failure. The high compressibility properties of soft clay are one of the major factor that could lead to high settlement. This is happened from the fact that soft clay are finer in particles and being too cohesive with the presence of water. High settlement are so dangerous as it could affects the movement of whole structure and would ended up with structure failures and cracks. Soft clay have the lowest value of permeability where water are hard to get through it particles and this is the reason why soft clay have a high moisture content. The presence of water could have made the soil become more unstable. Water could be the main agent that make the soil become unstable especially with the high ability of the soft clay soil to trap huge amount water within its particles. The soil particles have high tendency to bond closely with one another that make soft clay become easily compressed when undergoing compaction activity. By the weak conditions of the soil, the stiffness of the soil could easily be affected and this have made the soil become weak in strength. Strength of soil are the most vital part of any soil properties. Soil with weak strength could not sustain massive and high load on it. It becomes more dangerous when structures are built on the soft clay soil without having proper design and analysis to the soil. The structures are more subjected to fail rather than safe to be used. The development of any construction works in this type of soil perhaps the most challenging of all. The coastal area of Pekan is chosen mainly based on its strategic location to get undisturbed soft clay sample. Furthermore, shear strength analysis towards the soft clay soil could be useful for engineers from this field as it would be valuable in order to proceed with correct structural design, before any construction took place. The data indeed could also give extra dimension to the previous studies done in Pekan soft clay.
CHAPTER 2 LITERATURE REVIEW 2.1 Introduction Soil deposits can be divided into two (2) groups. One is residual soil, where the soil is created and formed from weathering process of rock and remains at the location of origin. Another one is transported soil where soil that moved from their place of origin (McCarthy, 2007). Soil may also be separated into three (3) very broad categories which are cohesionless, cohesive and organic soil. Cohesionless soil are gravel, sand and silt. This type of soil particles do not tend to stick together. Organic soil is described as soil containing a sufficient amount of organic matter to affect its engineering properties. While cohesive soils are soil that characterized by very small particle size where surface chemical predominate and in other words, the particles tend to stick to others (Liu & Evett, 2005). Basically, the most common type of cohesive soil is clay as the soil particles are closer together. Many areas in Malaysia have soft clay soil as the major soil distribution percentage. This is happened from the fact that Malaysia has many parts of coastal areas and also rivers that located in many state in peninsular Malaysia. Fine grained saturated
soils are believed to be located at many near coastal and river area (Schaefer, 1997). In peninsular Malaysia, the areas that consist of soft clay area are shown in Figure 2.1. The location for the study is located in Pekan. Figure 2.1: Soft clay area in peninsular Malaysia (Chin, 2005) According to McCarthy (2007), clay soil has particle sizes less than about 0.005mm. Soft clay soil can not be separated by sieve analysis test because the particles are too fine where no practical sieve can be made with the openings so small. Instead, the soil can be tested and determined by observing settling velocities of the particles in a water mixture. Soft clay soil is also subjected to be plasticity high when mixed with optimum amount of water. Any structure built on soil is subjected to settlement. But for soft clay soil, the chances of settlement to happen are greater. Excessive settlement is tipped to be a big problem as it often exceeds the permissible limits (Craig, 2004). Settlement will affect the stability of structure. Some possible damages are cracked foundations and cracked
columns of the structure. Correspondingly, if cracks appear in the structure, it is assumed that the foundation did move and could cause cracking. As building loads are applied to the ground there are possibilities of settlement to occur as a result of instantaneous compression of the soil. Under certain conditions, however, fine-grained soils will continue to compress under constant load for many years. This long-term compression is called consolidation settlement and is caused by the squeezing out of water from the pores in the clay. However, some measures could be taken to overcome the problem, such as (Schaefer, 1997):- a) Deep foundations could be driven through the unsuitable soils thereby avoiding them altogether. b) Excavate and replace the soft soils with suitable soils. c) Stabilize the soft soils with injected additives. 2.2 Classification of Soil Soil which have different properties but similar in some aspects may be classified into groups and sub-groups according to their engineering behavior. Figure 2.2 indicates of how the classification of soil being grouped using two major classification system in soil engineering based on grain size. American Association of State Highway and Transportation Officials (AASTHO) system defined that clay particles are less than 0.002mm size. However, Unified Soil Classification System (USCS) system stated that silt and clay are generally in the same grain sizes which are less than 0.075mm (Das, 2006). Classification systems of soil provide the explanations of the general characteristics of soils, which is generally based on soil parameters.
Figure 2.2: Soil classification based on grain size (Das, 2006) 2.2.1 American Association of State Highway and Transportation Officials Classification System American Association of State Highway and Transportation Officials (AASTHO) system was developed in 1929 as Public Road Administration classification system. AASTHO system defined that clay particles are less than 0.002mm grain size. The system provides a classification of soil using seven major groups; A-1 until A-7. Soils which are classified under A-1, A-2 and A-3 are known as granular materials which 35% or less of the particles pass through the No.200 sieve. Particles in group A-3, A-4, A-5, A-6 and A-7 are mostly silt and clay-type materials as more than 35% pass through the No.200 sieve (Das, 2006). The classification is as shown in Table 2.1
Table 2.1: American Association of State Highway and Transportation Officials (AASTHO) classification criteria (Das, 2006) Criteria Description Grain size a) Gravel: Fraction passing the 75mm sieve and retained on the No.10 US sieve b) Sand: Fractions passing the No.10 US sieve and retained on the No.200 US sieve c) Clay and Silt: Fractions passing the No.200 US sieve 2.2.2 Unified Soil Classification System Unified Soil Classification System (USCS) system is more preferred to be used by geotechnical engineer as accordance in American Society for Testing and Material (ASTM) in D-2487 standard requirement. This system is recovered by Casagrande in 1942 during engineering work in World War. The system classified coarse-grained soils that are gravelly and sandy in nature with less than 50% passing through the No.200 sieve. The group symbols are GW, GP, GM, GC, SW, SP, SM and SC. The symbols that started with a prefix G stands for gravel or gravelly soil and symbol that started with S are sand or sandy soil (Liu & Evett, 2005). The other symbols used are W for well graded soil and P for poorly graded soil. However, fine-grained soils are 50% or more passing through the No.200 sieve with symbols of M, which represent inorganic silt, C for inorganic clay, or O for organic silts and clay. The symbol of Pt is for peat, muck and other highly organic soils (Das, 2006). Table 2.2 shows how soils are identified according to the letter of group symbol.
Table 2.2: First and second letters of group symbols (Aysen, 2005) Soil Identification First Letter of Group Symbol Second Letter of Group Symbol Coarse grained soil G: gravel, S: sand W: Well graded P: Poorly graded Fine grained soil M: silt, C: clay L: Low plasticity (LL less than 50) H: High plasticity (LL more than 50) Organic soil O L: Low plasticity (LL less than 50) H: High plasticity (LL more than 50) Highly organic soils Pt No second letter 2.3 Clay Clay minerals are typically formed over long periods of time by the gradual chemical weathering of rocks (usually silicate-bearing) by low concentrations of carbonic acid and other diluted solvents. Soft Clay has particle sizes less than about 0.002mm or easily break down to this size (Liu & Evett, 2005). Figure 2.3 shows how the particles size distribution of soil and soft clay in terms of diameter in millimeter (mm). Soft clay is the finest of all and even it can only be clearly monitored by using microscopic tools. Soft clay is part of fine grained soil, with soil grains finer than 0.075mm. According to Unified Soil Classification System (USCS), clay soil is classifies as small particle soil that 50% pass sieve No.200 Specification US (0.075mm). According to Brand & Brenner (1981), soft clay is defined as clay with shear strength less than 25kPa. The strength of clay is low by comparing with other type of soils. Aside from this, clay and silt soil are part of cohesive soil as their particles are closed together and tend to stick within its particles. When a soil that has 50% or more particles with sizes of 0.002mm or less, it is generally termed clay (Aysen, 2005).