ANALYSIS OF SLOPE STABILITY AND PROPOSED REMEDIAL WORK FOR

FAILURE SLOPE AT KUALA LUMPUR

YONG CHIN YUNG

A project report submitted in partial fulfilment of the

requirement for the award of degree of

Master of Engineering (Civil-Geotechnics)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

AUGUST 2014

iii

This project report is dedicated to my beloved father and mother

iv

ACKNOWLEDGEMENT

I would like to express my sincere appreciation to my project supervisor

Dr. Nor Zurairahetty for her fully support, guidance and encouragement. Without her

continued patience on guiding and criticizing, I may not able to complete my

research appropriately.

My sincere appreciation also extends to Mr. Chen Tian Hee who is an

experiences senior geotechnical engineer. Mr. Chen is a senior engineer who

provided clearly explanation and assistance at various occasions to my project. His

opinion and hints are very useful indeed.

Last but not least, I wish to dedicate my grateful to my beloved family

members and my friends for their cares, loves, generous encouragement and support

to complete my Master Project.

v

ABSTRACT

The objective of this study is to determine the cause of failure and evaluate

the slope stability in order to propose remedial measure for stabilization. The

investigate slope discussed in this paper is located at Persiaran Endah and within 10

kilometers from Kuala Lumpur. This slope is around 23 to 28 meter height and

approximate 550 to 66

0. The pertinent engineering properties were analyzed from

field test borings which were drilled up to 22 meters depth, seismic refraction survey,

inclinometer data, back analysis result, and engineer judgment. Back analysis was

carried out to estimate the mobilized shear strength of the problematic layer.

SLOPE/W program of Universiti Teknologi Malaysia was used for analysis. Based

on the result of the field investigation and numerical analysis the lowest factor of

safety (FOS) that evaluated from the existing slope in critical section was found to be

0.741. Therefore, soil nailing was recommended to reinforce the slope, which has an

acceptable FOS of 1.525 under static condition. Hence, the installation of soil

nailing, grid beam, and drainage were selected for remediation to ensure the long

term stability of the failure slope.

vi

ABSTRAK

Objektif kajian ini adalah untuk menganalisis punca kegagalan cerun serta

mencadangkan langkah pemulihan penstabilan cerun. Cerun yang dikaji dalam

projek ini adalah terletak di Persiaran Endah dan kira-kira jarak 10 kilometer dari

Kuala Lumpur. Cerun kajian ini adalah 23 hingga 28 meter tinggi dan anggaran

kecerunannya adalah 550 hingga 66

0. Sifat-sifat kejuruteraan yang berkaitan

dianalisis daripada borings yang telah digerudi sehingga kedalaman 22 meter, sismic

refraction survey, data inclinometer, back analysis, dan wajaran daripada jurutera.

Back analysis dijalankan untuk menganggarkan kekuatan ricih kerahan bagi lapisan

yang bermasalah. SLOPE/W program Universiti Teknologi Malaysia telah

digunakan dalam analisis tersebut. Berdasarkan keputusan penyiasatan sekitar dan

analisis berangka, faktor keselamatan terendah (FOS) yang dinilai pada kritikal cerun

seksyen adalah 0.741. Oleh itu, soil nailing telah dipasang untuk mengukuhkan cerun

denagn factor keselamatan 1.525 yang kukuh dalam keadaan statik. Kesimpulanya,

pemasangan soil nailing, grid beam, dan saliran pengailiran telah dicadangkan untuk

pemulihan supaya dapat memastikan kestabilan jangka panjang bagi cerun kegagalan

tersebut.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF ABBREVIATIONS xiv

LIST OF SYMBOLS xv

LIST OF APPENDICES xvi

1 INTRODUCTION

1.1 Background 1

1.2 Problem Statement 3

1.3 Aim and Objectives of Study 4

1.4 Scope of Research 4

viii

2 LITERATURE REVIEW

2.1 Introduction 6

2.2 Basic Requirement of Slope Stability Analysis 9

2.2.1 Geologic Conditions 9

2.2.2 Site Topography 10

2.2.3 Material Properties 10

2.2.4 Shear Strength 11

2.2.4.1 Drained Shear Strength 12

2.2.4.2 Drained Residual Shear Strength 12

2.2.5 Groundwater Conditions 13

2.3 Slope Stability Analysis 14

2.3.1 Factors Affecting Slope Stability 14

2.3.2 Limit Equilibrium Method 15

2.3.3 Method of Slices 16

2.3.3.1 Ordinary Method of Slices 17

2.3.3.2 Bishop’s Simplified Method 17

2.3.3.3. Janbu’s Method 18

2.4 Critical Slip Surface 19

2.5 Factor of Safety 19

2.6 Back Analysis 20

2.6.1 Application of Back Analysis in Analysis 21

2.6.2 Limitation of Back Analysis 22

2.7 SLOPE/W 22

2.8 Previous Study 23

2.9 Summary 25

ix

3 METHODOLOGY

3.1 Introduction 26

3.2 Field Observation 28

3.3 Data Collection 29

3.3.1 Surface Investigation 29

3.3.2 Subsurface Investigation 30

3.3.3 Laboratory Test 31

3.3.4 Rainfall Intensity Data 32

3.4 Experimental Methods 33

3.4.1 Standard Compaction Test 33

3.4.2 Triaxial Test (CIU) 35

3.5 Mohr Coulomb Analyses 37

3.6 SLOPE/W Software 40

3.6.1 Limit Equilibrium Methods 41

3.6.2 Defining the Problems 42

3.6.3 Slip Surface for Circular Failure Model 44

3.6.4 Verification and Computation 45

3.7 Conclusion 46

4 DATA AND ANALYSIS

4.1 Introduction 47

4.2 Back Analysis 47

4.3 Field Investigation 50

4.4 Soil Investigation Result 52

4.4.1 Geological Background 53

4.4.2 Borehole Result 54

4.4.3 Seismic Refraction Survey 54

4.5 Laboratory Testing and Interpretation 56

4.5.1 Soil Classification 56

x

4.5.2 Adopted Soil parameters 57

4.6 Slope Stability Analysis 58

4.7 Remedial Measure Recommendation 61

4.8 Summary 65

5 CONCLUSIONS AND RECOMMENDATIONS

5.1 Introduction 66

5.2 Conclusions 66

5.3 Recommendations 68

REFERENCES 69

APPENDICES 72

xi

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Summary of static equilibrium conditions in

different limit equilibrium methods of slices

17

3.1 Summary of the site information 29

3.2 Summary of site investigation at study area 30

3.3 Summary of laboratory tests 31

3.4 Results from the Mohr’s circle analysis 38

3.5 Basic soil properties for slope stability analysis 40

4.1 Properties range in sensitivity study 48

4.2 The value of the parameter and the computed

factor of safety

50

4.3 Characteristics of soil, hard material and rock 55

4.4 Main regional soil strength parameters 58

4.5 Adopted soil parameters in the analysis 58

4.6 Summary of FOS for different slip surface

options

60

4.7 Summary of FOS for different LEM method 60

4.8 Summary of remedial work 62

xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Site Location (Google Map) 5

2.1 Falls 8

2.2 Topple 8

2.3 Slide 8

2.4 Spread 8

2.5 Flow 8

2.6 Depiction of forces acting on a typical slice 16

2.7 c’ and ’ from back analysis of an intact and

failed slope

21

3.1 Plan of slope failure that under study 26

3.2 Flow chart of the research methodology 27

3.3 Slope failure at the section GG’ 28

3.4 Rainfall intensity near to study area 32

3.5 Triaxial apparatus 36

3.6 Graphical representation of Coulomb shear

strength equation

37

3.7 Mohr-Coulomb failure envelope 37

3.8 Undrained shear envelope 38

3.9a Mohr’s circle for sample UD/1 39

3.9b Mohr’s circle for sample UD/1 39

3.10 Slope stability analysis processes using Slope/W 41

3.11 Slip surface option 42

3.12 Entry and Exit point range 43

xiii

3.13 Assigned pore water pressure to the geometry 43

3.14 Key in material properties 44

3.15 Assigned material properties to the geometry 44

3.16 Verifying the input data 45

3.17 Solve dialog box 45

3.18 FOS of the slope 46

4.1 Actual slope that modelled in SLOPE/W 48

4.2 Sensitivity analysis 49

4.3 Slope failure happened in year 2008 & 2012 51

4.4 Explanatory diagram of water infiltration

induced slope failure

51

4.5 Wet soil indicate high content of water 52

4.6 Simplified geological map 53

4.7 Soil classification base on British Soil

Classification System

56

4.8 Plasticity chart 57

4.9 Slope stability analysis for section GG’ 60

4.10 Slope stability analysis for section HH’ 61

4.11 Typical dimensions of soil nailing application

based on slope angle

62

4.12 Remedial analysis for soil nailing 63

4.13 Remedial analysis for hybrid anchor 63

4.14 Example of finishing soil nailing with shotcreted 64

xiv

LIST OF ABBREVIATIONS

FS = Factor of Safety

FOS = Factor of Safety

F = Factor of Safety

ZR = Right Inter-slice Force

hR = Height of the ZR

CIU = Isotropic Consolidation Undrained Test

JKR = Jabatan Kerja Raya

BH = Borehole

INC = Inclinometer

SG = Specific Gravity

MC = Moisture Content

JPS = Jabatan Pengaliran & Saliran

UD = Undisturbed Sample

SPT = Standard Penetration Test

LEM = Limit Equilibrium Method

xv

LIST OF SYMBOL

cu = Unconfined Shear Strength

c’ = Drained Shear Strength

δ = Inter-slice Force Inclination Angle

c = Cohesion

υ = Angle of Internal Friction

’

=

=

Effective Friction Angle

Friction Angle

σ3 = Cell Pressure

σ3’ = Effective Consolidation Pressure

ub = Pore Water Pressure

ui = Steady Pore Pressure

δVc = Total Change in Volume

τ = Shear Strength

σ´n = Normal Stress

xvi

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Overall Site Layout 73

B Mohr-Coulomb Analyses BH/4 74

C Inclinometer Result 76

D Piezometer Result 77

E Rainfall Intensity Data 78

F Simplified Borehole Profile 79

G Depth versus SPT-N Chart 80

H Line 2 Seismic Tomogram 81

I Slope Stability Analysis 82

CHAPTER 1

INTRODUCTION

1.1 Background

The developments in soil and rock mechanics play an important role in the

evolution of slope stability analyses in geotechnical engineering. The increasing

demand for the engineered cut and fill slopes in construction projects has enhanced

the needs for deepened understanding on the analytical methods, investigation tools

and stabilization methods in order to solve slope stability problems. (Abramson et

al., 2002)

In Malaysia, landslide records from the year 1966 to 2003 showed that 42%

of landslides occurred in hilly terrain areas and more than 90% occurred in

developed area such as in the infrastructural area, residential area and commercial

area. In order to carried out more investigation works for landslides in 2004, Public

Works Department Malaysia has establish a new branch called Slope Engineering

Branch that involved in mitigation, research and development, risk management,

safety and planning on slope and etc. (Slope Engineering Branch, 2010)

Slope Engineering Branch Malaysia state that the investigations carried out

thus far revealed that causes of landslides are due to physical, geological and human

elements. Based on landslide forensic statistical data for large scale failure from year

2004 to 2007, it was found that about 57% of landslides were due to human factor,

whereas 29% were attributed to physical factor and 14% was caused by various geo-

2

logical factors. It has also discovered that most of the landslides occurred at

manmade slopes.

With the incresed developments that have encroached into the hilly areas over

the pass two decades, Malaysia experience frequent landslides with a number of

major slope failure which cause damage and incovenience to the pulic. Among the

most notorious landslides was the colloapse of a slope with rubble wall, bringing

down Tower 1 Apartment of Highland Towers and killing 48 people on 11th

December 1993. The towers were built in 1978 at Taman Hillview, Hulu Klang

Selangor. (Gue & Cheah , 2007)

This landslide tragedy should be a good lessons for the relevant parties in

Malaysia so that improvement and more effective precaution measures can be taken

by them to avoid the destruction of lives and properties. Landslides not only bring

detrimental effects to the environment, but to the people and the economy as well.

Therefore, a reliable slope stability analysis should be carried out so that similar

incidents can be avoided in future.

To deal with these slope stability issues various approaches have been

adopted and developed over the years. The approaches now have been more of

computational rather than the manual. Various software are available to analyze the

slopes that are liable to failure by the calculating the factor of safety. Among the

famous approach are finite elements and limit equilibrium methods.

However, when using limiting equilibrium methods to analyze slopes, several

numerical inconsistencies and computational difficulties may occur in locating the

critical slip surface (depending on the geology) and hence establishing a factor of

safety. Despite these inherent limitations, due to its simplicity limiting equilibrium

continues to be the most commonly used approach (N. A. Hammouri et al. 2008).

Program SLOPE/W is formulated in terms of moment and force equilibrium factor of

safety equations. Limit equilibrium methods that used in this program include

Morgenstern-Price, General limit equilibrium, Spencer, Bishop, Ordinary, Janbu etc.

3

Hence, SLOPE/W is a main program that being chose to conduct the slope stability

analysis in various cases.

1.2 Problem Statement

Slope stability analysis is a vital analysis especially in a construction project

nearby the slope area. This analysis is performed to assess the safe design of human-

made or natural slopes and the equilibrium conditions. Improper slope analysis

design might cause slope failure which has been acknowledge as one of the most

frequent disaster that can lead to great loss of properties and life. Thus, the initial

soil investigation has to be done properly in order to achieve the actual soil condition

for the certain place where we want to start construction.

However, the stability of sloped land areas, landslide, is a main concern

where movements of existing or planned slopes would have an effect on the safety of

people and property or the usability and value of the area. Although, a lot of slope

analysis had carried out, but the possible of slope failure is still high. The quoted

phenomena take place due to either an incorrect approach to the assessment of their

stability, or mistakes made at the stage of geotechnical investigations, erroneous

assumptions made in the phase of carrying out calculation, or an improper location of

machines on the slope surcharge. One of the causes of the incorrect assessment of

slope stability may be inaccurate determination of the geological structure of the

slope in question. (Das, 2011)

Based on the Jabatan Pengairan dan Saliran Malaysia (JPS), Kuala Lumpur

was experienced a high intensity rainfall on March 2012. Consequently, three slope

failures were reported to occur along Jalan Persiaran Endah. These slope failures are

categorized as critical level because it is located beside the main road to a tourist spot

and just occur beside the residence areas. When slope failure occurs, the debris

encroaches on the road and may also cause damage to lives and properties from time

to time. Hence, the public safety is threatened directly and the immediately

4

remediation should be commenced. Therefore, this study is intended to carry out a

slope stability analysis on failure slope and in the same time, propose some remedial

measures based on the field investigation and stability analysis of the slope .

1.3 Aim and Objectives of Study

The aim of this study is to investigate the stability of the slopes by

determining the factor of safety and to proposed safe slopes at Jalan Pesiaran Endah,

Seputeh, Kuala Lumpur. Therefore, the objectives of this project are:

i. To identify the main cause of slope failure along Persiaran Endah,

Kuala Lumpur.

ii. To ascertain the design parameters and stability of the failure slopes

based on the SLOPE/W 2007 programme.

iii. To determine the appropriate remedial method on slope failure in term

of factor of safety.

1.4 Scope of Research

The investigation is limited to the colapsed section (hereafter will be referred

to as the investigated slope). SLOPE/W programme (by GEO-SLOPE) is use to

analyze the probability of failure of a slope. The minimum factor of safety will be

computed by using the critical parameters from the soil investigation reports data and

back analysis results. The data consists of soil investigation report which is gathered

from one related consultant company’s project. The case study is located at Persiaran

Endah Seputeh 50460, Wilayah Persekutuan Kuala Lumpur. This site can be

accessed via Jalan Robson and it is within 10 km from Kuala Lumpur City Centre.

The study area consists of three slopes failure namely Site 1, 2 and 3 and all are

different in geometry. However, in this study, the detail study on slope stability

analysis is only performed on failure slope at site 2 (section GG’ and HH’). This is

5

because site 2 is more critical in term of geometry if compare to another two sites.

The location of case study is shown in Figure 1.1.

Figure 1.1: Site Location (Google Map)

Failure Area

COORDINATE :

N = 3° 07’ 30.57’’

E = 101° 41’ 14.51’’

Investigated slope: Site 2

Site 3

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