Faculty of Engineering

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1 Faculty of Engineering PARAMETRIC STUDY OF RETAINING WALL USING PLAXIS Maqueline Cyndi Anak Nap Bachelor of Engineering with Honours (Civil Engineering) 2010

2 UNIVERSITI MALAYSIA SARAWAK R13a BORANG PENGESAHAN STATUS TESIS Judul: PARAMETRIC STUDY OF RETAINING WALL USING PLAXIS SESI PENGAJIAN: 2009/2010 Saya MAQUELINE CYNDI ANAK NAP (HURUF BESAR) mengaku membenarkan tesis * ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dengan syarat-syarat kegunaan seperti berikut: 1. Tesis adalah hakmilik Universiti Malaysia Sarawak. 2. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Membuat pendigitan untuk membangunkan Pangkalan 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 yang berkenaan SULIT TERHAD (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972). (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/ badan di mana penyelidikan dijalankan). TIDAK TERHAD Disahkan oleh (TANDATANGAN PENULIS) (TANDATANGAN PENYELIA) Alamat tetap: D/A NAP AK. RISONG, CAW. KOMUNIKASI IPD SARIKEI, SARIKEI, SARAWAK. AHMAD KAMAL ABDUL AZIZ 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.

3 APPROVAL SHEET Final Year Project as follows: Title Author : Parametric Study of Retaining Wall Using PLAXIS : Maqueline Cyndi Anak Nap Matrics number : Read and approved by: En. Ahmad Kamal Abdul Aziz Date Project Supervisor

4 PARAMETRIC STUDY OF RETAINING WALL USING PLAXIS MAQUELINE CYNDI ANAK NAP This report is submitted to Faculty of Engineering, Universiti Malaysia Sarawak (UNIMAS) as to fulfil the requirements of Bachelor Degree with Honours (Civil Engineering) 2010

5 To my love and special ones Mummy and Daddy thanks for your never end care, support, understanding and concern. I will always love you Sisters thanks for your support and attention Jimmy thanks for your love, understanding and for always be by my side Mr. Ahmad Kamal Abdul Aziz a very thank you for giving me the opportunity to do the research under your supervision and the priceless knowledge you gave to me Friends thanks for all your helps and brilliant ideas All of you inspire my effort and achievement Even thousand words could not express my gratitude

6 ACKNOWLEDGEMENT I would like to take this golden opportunity to acknowledge my grateful to all people that I have come in contact for their help, advice, guidance and assistance throughout the process of completing this thesis. First of all, I would like to express my outmost gratitude to my supervisor, Mr. Ahmad Kamal Abdul Aziz for willingly being my supervisor and sharing his skills, knowledge, and experiences as well as understanding and guidance in the topic of my study. Without his continued support, this research would not have been the same as presented here. My deepest gratitude also goes to my beloved parents and sisters for their never ending love and care, continuing financial, moral support, and understanding throughout my studies. My sincere appreciation also goes to Jimmy Voon for his full understanding and never ending support, love and care. Last but not least, I am grateful to all my friends for their contribution of ideas and support along the process of preparing this thesis. ii

7 ABSTRAK Tembok penahan adalah sejenis struktur kejuruteraan generik yang digunakan untuk menahan daya ufuk bumi yang disebabkan oleh permukaan tanah atau kambusnya yang tegak atau hampir tegak. Tanah di belakang tembok mungkin sama ada benteng semula jadi atau tanah yang dikambus balik yang diletakkan bersebelahan dengan tembok penahan. Tembok-tembok penahan harus direka dengan berhati-hati agar mampu menahan daya ufuk bumi yang cenderung menyebabkan kegagalan kepada struktur tersebut. Jenis tembok penahan yang sesuai digunakan adalah bergantung kepada keadaan sebenar di tapak atau keadaan tanah, interaksi antara jisim tanah dan tembok penahan, magnitud, dan taburan tekanan tanah sisi. Dalam kajian ini, analisis dan kajian parameter untuk tembok cerucuk keping dijalankan dengan menggunakan perisian elemen terhad, PLAXIS V8. Satu model elemen terhad telah dibuat untuk menganalisa tembok cerucuk keping dengan nilai yang berbeza bagi setiap parameter seperti kepaduan tanah, sudut geseran dalam, panjang tembok cerucuk keping, kedalaman korekan tanah dan beban tambahan. Perbezaan nilai parameter itu boleh menjejaskan momen lentur dan sesaran tembok cerucuk keping seperti yang disampaikan dan dibincangkan dalam kajian ini. iii

8 ABSTRACT Retaining wall is a type of generic engineering structure that is employed to restrain lateral forces exerted by a vertical-faced or near-vertical-faced mass of earth. The earth behind the wall may be either the natural embankment or the backfill material placed adjacent to the retaining wall. Retaining walls must be design carefully to withstand lateral pressure of the earth, which tends to cause a failure of the structure. A suitable type of retaining wall to be used depends on the site or soil condition, reciprocal action between soil mass and the retaining wall, magnitude, and the distribution of the lateral earth pressure. In this study, the analysis and the parametric study of a sheet pile wall is done by using finite element software, PLAXIS V8. A finite element model has been developed to analyze the behaviour of sheet pile wall with different value of each parameter such as soil cohesion, angle of internal friction, length of the sheet pile wall, depth of excavation and surcharge load. The different value of the parameter may affect the bending moment and the displacement of the sheet pile wall which are presented and discussed in this study. iv

9 TABLE OF CONTENTS CONTENT PAGE NO. ACKNOWLEDGEMENT ABSTRAK ABSTRACT TABLE OF CONTENT LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS ii iii iv v x xi xv CHAPTER I INTRODUCTION 1.1 General Problem statement Objective of study Scope of study 4 CHAPTER II LITERATURE REVIEW 2.1 Introduction Types of Retaining Walls Analysis of Retaining Walls Lateral Earth Pressure Surcharge Load 26 v

10 2.3.3 Effect of Water Pressure Earthquake Load Compaction Stability of Retaining Walls Overturning Sliding Bearing Capacity Deep-seated Shear Excessive Settlement Finite Element Method 33 CHAPTER III METHODOLOGY 3.1 General Description of Finite Element Program, 39 PLAXIS 3.3 General Modeling Aspects Types of Element Nodes Stress points Mohr-Coulomb Model Young s modulus, E Cohesion, c Unit weight, Friction angle, Dilatancy angle, 47 vi

11 3.4.6 Poisson s ratio, v Retaining Wall Design Example Input Data Mesh Generation Initial Conditions Output Conclusion 57 CHAPTER IV ANALYSIS, RESULT AND DISCUSSION 4.1 General Details of the retaining wall Case study one: Effect of soil cohesion, c to 60 the retaining wall Case one: Cohesionless soil, c = Case two: Soil cohesion, c = 10 kn/m Case three: Soil cohesion, c = 20 kn/m Case study two: Effect of angle of internal 66 friction, to the retaining wall Case one: Angle of internal friction, 66 = 25º Case two: Angle of internal friction, 68 = 35º Case three: Angle of internal friction, 69 = 45º 4.5 Case study three: Effect of the length of sheet 71 pile wall, L to the retaining wall vii

12 4.5.1 Case one: Length of sheet pile wall, 72 L = 20 m Case two: Length of sheet pile wall, 73 L = 25 m Case three: Length of sheet pile wall, 75 L = 30 m 4.6 Case study four: Effect of depth of excavation, 77 D to the retaining wall Case one: Depth of excavation, 77 D = 15 m Case two: Depth of excavation, 79 D = 20 m Case three: Depth of excavation, 80 D = 25 m 4.7 Case study five: Effect of surcharge load, q to 82 the retaining wall Case one: Surcharge load, q = 10 kn/m Case two: Surcharge load, q = 100 kn/m Conclusion 86 CHAPTER V CONCLUSION AND RECOMMENDATION 5.1 General Conclusion Recommendation 90 REFERENCES 91 viii

13 APPENDIX APPENDIX A 94 APPENDIX B 97 APPENDIX C 100 APPENDIX D 103 APPENDIX E 106 APPENDIX F 109 APPENDIX G 112 APPENDIX H 115 APPENDIX I 118 APPENDIX J 121 APPENDIX K 124 APPENDIX L 127 APPENDIX M 130 APPENDIX N 133 ix

14 LIST OF TABLES Table Page No. 2.1 Types of retaining wall Types of failure of retaining wall Six parameters for Mohr-Coulomb soil model Mohr-Coulomb soil parameter used in the analysis Summary for case study one Summary for case study two Summary for case study three Summary for case study four Summary for case study five 86 x

15 LIST OF FIGURES Figure Page No. 2.1 Types of retaining wall Other types of retaining wall Concept of lateral earth pressure Types of lateral earth pressure Stress at rest Rankine active pressure Rankine passive pressure Coulomb s active earth pressure Coulomb s passive earth pressure Failure of retaining wall: (a) by overturning; (b) by 30 sliding; (c) bearing capacity; (d) by deep-seated shear 3.1 Flow chart of the study node triangular element node triangular element Stress circles at yield, one touches Coulomb s 46 envelope xi

16 Figure Page No. 3.5 Geometry model Finite element mesh of the geometry Initial stresses in the geometry Selecting point of curve Deformed mesh Total displacements Horizontal displacements Vertical displacements Total increments Horizontal increments Vertical increments Total stresses Effective stresses Active pore pressures Geometry model of the analysis Wall bending moment for c = 0 is knm Wall horizontal displacement for c = 0 is m Wall bending moment for c = 10 kn/m 2 is knm 4.5 Wall horizontal displacement for c = 10 kn/m 2 is m xii

17 Figure Page No. 4.6 Wall bending moment for c = 20 kn/m 2 is knm 4.7 Wall horizontal displacement for c = 20 kn/m 2 is m 4.8 Wall bending moment for = 25º is knm Wall horizontal displacement for = 25º is m Wall bending moment for = 35º is knm Wall horizontal displacement for = 35º is m Wall bending moment for = 45º is knm Wall horizontal displacement for = 45º is m Wall bending moment for L = 20 m is knm Wall horizontal displacement for L = 20 m is m Wall bending moment for L = 25 m is knm Wall horizontal displacement for L = 25 m is m Wall bending moment for L = 30 m is knm Wall horizontal displacement for L = 30 m is m Wall bending moment for D = 15 m is knm Wall horizontal displacement for D = 15 m is m 4.22 Wall bending moment for D = 20 m is knm Wall horizontal displacement for D = 20 m is m xiii

18 Figure Page No Wall bending moment for D = 25 m is knm Wall horizontal displacement for D = 25 m is m 4.26 Wall bending moment for q = 10 kn/m 2 is knm 4.27 Wall horizontal displacement for q = 10kN/m 2 is m 4.28 Wall bending moment for q = 100 kn/m 2 is knm 4.29 Wall horizontal displacement for q = 100 kn/m 2 is m xiv

19 LIST OF SYMBOLS c - Cohesion D - Depth of excavation E - Young s modulus H - Height K - Lateral earth pressure coefficient L - Length of sheet pile wall q - Surcharge load u - Pore water pressure V - Total volume of soil v - Poisson s ratio W - Total weight of soil z - Depth OCR - Overconsolidation ratio PI - Plasticity index - Angle of internal friction - Unit weight - Dilatancy angle FS (bearing capacity) - Factor of safety against bearing capacity failures F d - Horizontal driving force FS (overturni ng) - Factor of safety against overturning F R - Horizontal resisting force xv

20 FS (sliding) - Factor of safety against sliding K o - Coefficient of earth pressure at rest K a - Coefficient of earth pressure at active state K p - Coefficient of earth pressure at passive state M O - Moment causing overturning M R - Moment resisting overturning P a - Total active earth pressure force P p - Total passive earth pressure force q max - Maximum contact pressure q u - Ultimate bearing capacity W s - Weight of soil solids W w - Weight of water ' a - Active earth pressure ' h - Horizontal effective stress ' p - Passive earth pressure ' v - Vertical effective stress w - Unit weight of water ' - Effective stress xvi

21 CHAPTER I INTRODUCTION 1.1 General Infrastructure development in Malaysia has grown up as the population increases and development becomes a priority. With the blooming development on hill-sites, slope failures can be seen especially during raining seasons or after heavy prolong downpours. Slope failures not only will cause economic loss to the public but also may result in loss of life. Effective remedial works can then be designed and carried out. In selecting the most suitable remedial measure, it must be able to rectify the problem and can satisfy other constraints such as the site condition, constructability, cost and time. Various remedial measures can be used for a failed slope. Amongst the various slope repair measures, retaining structures measure is generally more suitable when there are certain site constraints in particular when the available space is limited. Retaining wall, an earth retaining structure is one of the important structures widely used in many constructions in Malaysia, in areas that commonly involve in cutting or backfilling slopes. Retaining walls are structures that support soils at 1

22 slopes of a few steeper than their angle of repose. These slopes may be capable of self-support, but in other instances lateral-retaining structures will be required to provide adequate support to the slope. If adequate space exists, consideration of slope can be taken, whereas a retaining wall is required if adequate space is not available. Maximum slope steepness is dictated by the quality of fill soil available and whether or not the slope will be protected with riprap to eliminate the need for mowing and other maintenance. To design retaining walls properly, an engineer must know the basic parameters (the unit weight, angle of internal friction, and cohesion) of the soil retained behind the wall and the soil below the based slab. The most important consideration in proper design and installation of retaining walls is that the retained material is attempting to move forward and downslope due to gravity. Lateral earth pressures are typically smallest at the top of the wall and increase toward the bottom. Earth pressures will push the wall forward or overturn it if not properly addressed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes an additional horizontal hydrostatic pressure on the wall. Knowing the properties of the soil behind the wall enables the engineer to determine the lateral pressure distribution that has to be design for. 2

23 1.2 Problem Statement The designs of retaining wall and construction methods which involve cut and fill as well as compaction, contribute significantly to the development of lateral earth pressure and its distribution. Therefore, appropriate design analysis is of great importance to be conducted. Before this time, there are few fundamental theories and formulas or rules by Coulomb (1776), Rankine (1857), Terzaghi and Peck (1967), and Casagrande (1973). All these theories and formulas are until now being used to analyze and designing the retaining wall. The earlier researches have recognized an importance for consistent understanding and application for retaining wall analysis for construction and remediation projects. These analyses are generally carried out at the beginning of a project, and sometimes throughout the life of a project during planning, design, construction, maintenance and rehabilitation. Design of retaining wall has traditionally been carrying out using simplified method of analysis such as Limit Equilibrium Method and empirical approaches. All of these methods are based on simplified analysis. Thus, they cannot provide the engineer with all the desired design information and only provide very limited indications of soil movements. The introduction of numerical or finite element software has resulted in considerable advances in the analysis and design of retaining structures. Therefore, it is of great encouragement to study and understand the use of this software in solving practical problem of retaining wall. The water table is assumed to be at considerable depth below the bottom of the wall. Therefore, its effect could be neglected. 3

24 1.3 Objective of Study In this study, the objectives are including: a) To understand the types of retaining wall, their stability and failure that may occurs to the structure. b) To familiar with geotechnical engineering software, PLAXIS in solving geotechnical problems. c) To use geotechnical engineering software, PLAXIS to simulate and analyze the behavior of retaining wall structure. d) To solve a parametric study of retaining wall using finite element software, PLAXIS. 1.4 Scope of Study The scope of this research is to study and understand the behavior of retaining wall structure and the application of finite element method in solving retaining wall problem. The analysis done is based on research and reports obtained, from publish literature and also from relevant party and authority. The main focus of this study will be on the use of PLAXIS software to do the analysis of the retaining wall. The effect of the properties of soil and other parameters such as length of retaining wall, depth of excavation and surcharge load to the retaining wall is also taking into account. 4