PARAMETRIC STUDY OF RETAINING WALL USING PLAXIS
Maqueline Cyndi Anak Nap
Bachelor of Engineering with Honours (Civil Engineering)
2010
Faculty of Engineering
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 (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972).
TERHAD (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, AHMAD KAMAL ABDUL AZIZ
Nama Penyelia 96100 SARIKEI, SARAWAK.
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.
APPROVAL SHEET
Final Year Project as follows:
Title : Parametric Study of Retaining Wall Using PLAXIS Author : Maqueline Cyndi Anak Nap
Matrics number : 16601
Read and approved by:
_________________________ _________________________
En. Ahmad Kamal Abdul Aziz Date
Project Supervisor
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
…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
ii
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.
iii
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.
iv
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.
v
TABLE OF CONTENTS
CONTENT PAGE NO.
ACKNOWLEDGEMENT ii
ABSTRAK iii
ABSTRACT iv
TABLE OF CONTENT v
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF SYMBOLS xv
CHAPTER I INTRODUCTION
1.1 General 1
1.2 Problem statement 3
1.3 Objective of study 4
1.4 Scope of study 4
CHAPTER II LITERATURE REVIEW
2.1 Introduction 5
2.2 Types of Retaining Walls 6
2.3 Analysis of Retaining Walls 13
2.3.1 Lateral Earth Pressure 14
2.3.2 Surcharge Load 26
vi
2.3.3 Effect of Water Pressure 27
2.3.4 Earthquake Load 28
2.3.5 Compaction 28
2.4 Stability of Retaining Walls 29
2.4.1 Overturning 30
2.4.2 Sliding 31
2.4.3 Bearing Capacity 32
2.4.4 Deep-seated Shear 33
2.4.5 Excessive Settlement 33
2.5 Finite Element Method 33
CHAPTER III METHODOLOGY
3.1 General 37
3.2 Description of Finite Element Program, 39 PLAXIS
3.3 General Modeling Aspects 40
3.3.1 Types of Element 41
3.3.2 Nodes 42
3.3.3 Stress points 43
3.4 Mohr-Coulomb Model 43
3.4.1 Young’s modulus, E 44
3.4.2 Cohesion, c 45
3.4.3 Unit weight, 45
3.4.4 Friction angle, 46
3.4.5 Dilatancy angle, 47
vii
3.4.6 Poisson’s ratio, v 47
3.5 Retaining Wall Design Example 47
3.5.1 Input Data 48
3.5.2 Mesh Generation 48
3.5.3 Initial Conditions 49
3.5.4 Output 51
3.6 Conclusion 57
CHAPTER IV ANALYSIS, RESULT AND DISCUSSION
4.1 General 58
4.2 Details of the retaining wall 59
4.3 Case study one: Effect of soil cohesion, c to 60 the retaining wall
4.3.1 Case one: Cohesionless soil, c = 0 61 4.3.2 Case two: Soil cohesion, c = 10 kN/m2 62 4.3.3 Case three: Soil cohesion, c = 20 kN/m2 64 4.4 Case study two: Effect of angle of internal 66
friction, to the retaining wall
4.4.1 Case one: Angle of internal friction, 66
= 25º
4.4.2 Case two: Angle of internal friction, 68
= 35º
4.4.3 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
viii
4.5.1 Case one: Length of sheet pile wall, 72 L = 20 m
4.5.2 Case two: Length of sheet pile wall, 73 L = 25 m
4.5.3 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
4.6.1 Case one: Depth of excavation, 77 D = 15 m
4.6.2 Case two: Depth of excavation, 79 D = 20 m
4.6.3 Case three: Depth of excavation, 80 D = 25 m
4.7 Case study five: Effect of surcharge load, q to 82 the retaining wall
4.7.1 Case one: Surcharge load, q = 10 kN/m2 83 4.7.2 Case two: Surcharge load, q = 100 kN/m2 84
4.8 Conclusion 86
CHAPTER V CONCLUSION AND RECOMMENDATION
5.1 General 88
5.2 Conclusion 88
5.3 Recommendation 90
REFERENCES 91
ix
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
x
LIST OF TABLES
Table Page No.
2.1 Types of retaining wall 6
2.2 Types of failure of retaining wall 29
3.1 Six parameters for Mohr-Coulomb soil model 44 4.1 Mohr-Coulomb soil parameter used in the analysis 59
4.2 Summary for case study one 65
4.3 Summary for case study two 71
4.4 Summary for case study three 76
4.5 Summary for case study four 82
4.6 Summary for case study five 86
xi
LIST OF FIGURES
Figure Page No.
2.1 Types of retaining wall 10
2.2 Other types of retaining wall 13
2.3 Concept of lateral earth pressure 15
2.4 Types of lateral earth pressure 15
2.5 Stress at rest 18
2.6 Rankine active pressure 20
2.7 Rankine passive pressure 22
2.8 Coulomb’s active earth pressure 24
2.9 Coulomb’s passive earth pressure 25
2.10 Failure of retaining wall: (a) by overturning; (b) by sliding; (c) bearing capacity; (d) by deep-seated shear
30
3.1 Flow chart of the study 38
3.2 15-node triangular element 42
3.3 6-node triangular element 42
3.4 Stress circles at yield, one touches Coulomb’s envelope
46
xii
Figure Page No.
3.5 Geometry model 48
3.6 Finite element mesh of the geometry 49
3.7 Initial stresses in the geometry 50
3.8 Selecting point of curve 51
3.9 Deformed mesh 52
3.10 Total displacements 52
3.11 Horizontal displacements 53
3.12 Vertical displacements 53
3.13 Total increments 54
3.14 Horizontal increments 54
3.15 Vertical increments 55
3.16 Total stresses 55
3.17 Effective stresses 56
3.18 Active pore pressures 56
4.1 Geometry model of the analysis 60
4.2 Wall bending moment for c = 0 is 1520.00 kNm 61 4.3 Wall horizontal displacement for c = 0 is 3.830 m 62 4.4 Wall bending moment for c = 10 kN/m2 is 530.28
kNm
63
4.5 Wall horizontal displacement for c = 10 kN/m2 is 1.010 m
63
xiii
Figure Page No.
4.6 Wall bending moment for c = 20 kN/m2 is 361.11 kNm
64
4.7 Wall horizontal displacement for c = 20 kN/m2 is 0.743 m
65
4.8 Wall bending moment for = 25º is 577.08 kNm 67 4.9 Wall horizontal displacement for = 25º is 1.060 m 67 4.10 Wall bending moment for = 35º is 292.94 kNm 68 4.11 Wall horizontal displacement for = 35º is 0.600 m 69 4.12 Wall bending moment for = 45º is 175.69 kNm 70 4.13 Wall horizontal displacement for = 45º is 0.440 m 70 4.14 Wall bending moment for L = 20 m is 1290.00 kNm 72 4.15 Wall horizontal displacement for L = 20 m is 3.850 m 73 4.16 Wall bending moment for L = 25 m is 957.40 kNm 74 4.17 Wall horizontal displacement for L = 25 m is 1.880 m 74 4.18 Wall bending moment for L = 30 m is 882.82 kNm 75 4.19 Wall horizontal displacement for L = 30 m is 1.700 m 76 4.20 Wall bending moment for D = 15 m is 882.82 kNm 78 4.21 Wall horizontal displacement for D = 15 m is 1.700
m
78
4.22 Wall bending moment for D = 20 m is 2820.00 kNm 79 4.23 Wall horizontal displacement for D = 20 m is 8.910
m
80
xiv
Figure Page No.
4.24 Wall bending moment for D = 25 m is 5020.00 kNm 81 4.25 Wall horizontal displacement for D = 25 m is 124.290
m
81
4.26 Wall bending moment for q = 10 kN/m2 is 1020.00 kNm
83
4.27 Wall horizontal displacement for q = 10kN/m2 is 1.980 m
84
4.28 Wall bending moment for q = 100 kN/m2 is 2660.00 kNm
85
4.29 Wall horizontal displacement for q = 100 kN/m2 is 10.290 m
85
xv
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
capacity) (bearing
FS - Factor of safety against bearing capacity failures
Fd - Horizontal driving force
ng) (overturni
FS - Factor of safety against overturning
FR - Horizontal resisting force
xvi
(sliding)
FS - 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 MO - Moment causing overturning
MR - Moment resisting overturning P a - Total active earth pressure force P p - Total passive earth pressure force qmax - Maximum contact pressure qu - Ultimate bearing capacity Ws - Weight of soil solids
Ww - 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
1
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
2
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.
3 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.
4 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.
