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CORRELATION BETWEEN SPT, MACKINTOSH PROBE AND 2-D RESISTIVITY VALUES FOR
SOILS STIFFNESS
TARMIZI
UNIVERSITI SAINS MALAYSIA
2017
CORRELATION BETWEEN SPT, MACKINTOSH PROBE AND 2-D RESISTIVITY VALUES FOR
SOILS STIFFNESS
by
TARMIZI
Thesis submitted in fulfilment of the requirements
for the degree of Master of Science
April2017
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ACKNOWLEDGEMENT
First and foremost, praise to Allah for giving me the strength and patience to
complete my thesis. I would like to thank my main supervisor Prof. Madya Dr. Rosli
Saad for his excellent guidance, support and continuous encouragement for this
research and thesis. This thesis has been strengthening by his comments and advice.
His invaluable suggestions and discussions had also helped me a lot. Similarly, to
extent my sincere gratitude to my co-supervisor Dr. Nordiana Mohd Muztaza for her
suggestion and continuous support. I also want to thank Prof. Dr. Mokhtar Saidin
from Centre of Archaeological Research (CGAR) for his financial support. My full
thanks to Dr. Nur Azwin Ismail for her useful discussions and suggestions. I also
want to thank Dr. Muhammad Syukri Usman for his suggestion and help me
whenever possible.
I am very gratefuls to Geophysics lab assistants, Mr. Yaakub Othman, Mr.
Shahil Ahmad Khosaini, Mr. Azmi Abdullah and Mr. Abdul Jamil Yusuf who helped
me in the field for data acquisition. Special thanks to all geophysics team who have
helped me in data collection and processing, Dr. Andy Anderson Berry, Mr. Zul
fadhli, Mr. Fauzi Andika, Mr. Muhammad Taqiuddin, Mr. Kiu Yap Chong, Mr.
Muhamad Afiq Saharudin, Mr. Hazrul Hisham Badrul Hisham, Mr. Amsir, Mr.
Sabrian Tri Anda , Mr. Azim Hilmy, Mr. Muhamad Iqbal Mubarak, Mr. Yakubu
Samuel Mingyi, Mr. Muhammad Sabiu Bala, Ms. Rose Nadia Abu Samah, Ms. Umi
Maslinda Anuar, Ms. Nur Amalina Mohd Khoirul Anuar, Ms. Nabila Sulaiman, Ms.
Nordiana Ahmad Nawawi, Ms. Nur Asmidah Aziz, Ms. Nur Khairunnisa Aqilah
Yunos and Ms. Noor Farah Izzati Ismail.
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Finally, I want to thank my parents Hasyim Anzib and Sakdiah, my sibling
Ms. Nurlaili, Mr. Husaini, Mr. Nazaruddin, Mr. Arif Maulana and friends for their
prayer, love, encouragement, and support throughout my study.
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TABLE OF CONTENT
Acknowledgement ii
Table of content iv
List of tables vii
List of figures ix
List of symbols xi
List of abbreviations xii
Abstrak xiii
Abstract xv
CHAPTER 1: INTRODUCTION 1
1.0 Background 1
1.1 Problem statement 3
1.2 Research objective 4
1.3 Scope of the study 5
1.4 Layout of thesis 5
CHAPTER 2: LITERATURE REVIEW 6
2.0 Introduction 6
2.1 Borehole method 6
2.2 2-D resistivity method 8
2.2.1 2-D resistivity imaging 10
2.2.2 Array 11
2.2.3 Resistivity of rock and mineral 13
2.3 Mackintosh probe 14
2.4 Previous study 15
2.5 Chapter summary 35
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CHAPTER 3: MATERIALS AND METHODS 36
3.0 Introduction 36
3.1 Study flow 36
3.2 Study area 37
3.2.1 USM, Pulau Pinang 38
3.2.2 Sungai Batu, Kedah 40
3.3 Data acquisition 42
3.3.1 Borehole 43
3.3.2 2-D resistivity method 44
3.3.3 Mackintosh probe 45
3.4 Survey lines 47
3.4.1 Study area USM, Pulau Pinang 47
3.4.2 Study area Sungai Batu, Kedah 48
3.5 Data processing 50
3.6 Chapter summary 51
CHAPTER 4: RESULTS AND DISCUSSIONS 52
4.0 Introduction 52
4.1 Results and discussion 52
4.1.1 Study area USM, Pulau Pinang 52
4.1.1.(a) Borehol result 53
4.1.1.(b) 2-D resistivity result 53
4.1.1.(c) Mackintosh probe result 54
4.1.1.(d) Correlation borehole 2-D resistivity and 55 mackintosh probe
4.1.2 Study area Sungai Batu, Kedah 58
4.1.2.(a) Borehole result 58
4.1.2.(b) 2-D resistivity result 62
4.1.2.(c) Mackintosh probe result 63
4.1.2.(d) Correlation borehole, 2-D resistivity and 66 mackintosh probe
4.2 Chapter summary 79
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CHAPTER 5: CONCLUSION AND RECOMMENDATIONS 80
5.0 Conclusion 80
5.1 Recommendations 81
REFERENCES 82
APPENDIXES
APPENDIX 1: Photos of survey lines
APPENDIX 2: Borehole records data
LIST OF PUBLICATION
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LIST OF TABLES
Page
Table 2.1 Resistivity value of some common materials and rocks 14
Table 3.1 List of equipments for 2-D resistivity imaging method 45
Table 3.2 List of equipments for mackintosh probe method 46
Table 4.1 Borehole (BH1) record at line 1 USM 53
Table 4.2 Mackintosh probe (MP1) record at line 1 USM 55
Table 4.3 The relation between resistivity, N-value and M-value for 57 USM soft soil
Table 4.4 Position of borehole and mackintosh probe at Sungai Batu 58
Kedah Table 4.5 Borehole record (BH2) at survey line LB1 59 Table 4.6 Borehole record (BH3) at survey line LB2 60 Table 4.7 Borehole record (BH4) at survey line LB3 61 Table 4.8 Borehole record (BH5) at survey line LB4 61 Table 4.9 Mackintosh probe record (MP2) at survey line LB1 64 Table 4.10 Mackintosh probe record (MP3) at survey line LB2 65 Table 4.11 Mackintosh probe record (MP4) at survey line LB3 65 Table 4.12 Mackintosh probe record (MP5) at survey line LB4 66 Table 4.13 The relation between resistivity, mackintosh probe and 69
borehole for line LB1 Table 4.14 The relation between resistivity, mackintosh probe and 71
borehole for line LB2 Table 4.15 The relation between resistivity, mackintosh probe and 73
borehole for line LB3 Table 4.16 The relation between resistivity, mackintosh probe and 75
borehole for line LB4
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Table 4.17 Intergation of resistivity value, mackintosh probe 75 and borehole at line LB1-LB4
Table 4.18 Resistivity value, N-value and M-value of Sungai Batu 77
soil Table 4.19 Resistivity values comparison with previous study 78 Table 5.1 Classification and summary the soil classification 81
according to geology setting
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LIST OF FIGURES
Page
Figure 2.1 Types of the boreholes (Hvorsles, 1948) 7
Figure 2.2 Four electrode array for subsurface resistivity measurement 9
Figure 2.3 The arrangement of electrode for 2-D resistivity imaging 11 survey and the sequence of measurements used to build up the resistivity section (Loke, 1999)
Figure 2.4 Common resistivity arrays and their geometric factor 12 (Loke and Barker, 1996)
Figure 2.5 Forward and reverse Pole-dipole array (Loke, 1999) 13
Figure 2.6 The illustration of mackintosh probe equipment 15 (Fakhrel et al., 2006)
Figure 2.7 Soil strength based on mackintosh probe test (Ayob et al.,2005) 16
Figure 2.8 Resistivity imaging of (a) Aligarh and (b) Jhansi 17
(Sudha et al., 2008)
Figure 2.9 SPT value vs resistivity plot (Sudha et al., 2008) 18
Figure 2.10 SPT vs transverse resistivity of two locations Aligarh 18
and Jhansi (Sudha et al., 2008)
Figure 2.11 2-D resistivity subsurface profile image obtained from 20
geoeletrical survey (Abidin et al., 2012)
Figure 2.12 SPT N-value versus resistivity (Ωm) at Kuala Upis 21
(Abidin et al., 2012)
Figure 2.13 SPT N-value versus resistivity (Ωm) at Tanjung Maung 21
(Abidin et al., 2012)
Figure 2.14 Correlations of electrical resistivity with (a) moisture content 23
(b) unit weight (siddiqui, 2012)
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Figure 2.15 Correlations of electrical resistivity with (c) Angle of internal 24
friction and (d) Cohesion of soil (siddiqui, 2012)
Figure 2.16 2D resistivity iversion of survey line Rawang, Slangor 25
(Saad et al., 2011)
Figure 2.17 2D resistivity inversion of Lembah Bujang (Muztaza et al., 2013) 26
Figure 2.18 2-D resistivity tomography section beneath profiles 30
(Elijah et al., 2012)
Figure 2.19 IP tomography section beneath profiles (Elijah et al., 2012) 30
Figure 2.20 3-D resistivity tomography beneath the study area 31
(Elijah et al., 2012)
Figure 3.1 Research flow chart 37
Figure 3.2 The location of the study area (Google Earth, 2016) 38
Figure 3.3 Location of study area and resistivity survey line at USM 39 Pulau Pinang (Google Earth, 2016)
Figure 3.4 Geological map of Pulau Pinang (Ong, 1993) 40
Figure 3.5 Study area at Sungai Batu Kedah (Google Earth, 2016) 41
Figure 3.6 Geological map of Sungai Batu Kedah (JMG, 1985) 42
Figure 3.7 Geometry illustration of 2-D resistivity data acquisition 44 (Dahlin, 1996) Figure 3.8 Equipment of 2-D resistivity method 45
Figure 3.9 Equipment of mackintosh probe method 46
Figure 3.10 Resistivity and mackintosh probe data acquisition 47
Figure 3.11 2-D resistivity survey lines at Sungai Batu Kedah 48
Figure 3.12 Borehole and mackintosh probe location at Sungai Batu 49 (Kedah) relatif to resistivity lines
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Figure 3.13 Resistivity and mackintosh probe data acquisition at 49 Sungai Batu
Figure 3.14 Resistivity section produce by RES2DINV software 50
Figure 4.1 2-D resistiviy inversion model of line 1 USM 54
Figure 4.2 Correlation between resistivity value, N-value and M-value 56 of line 1 2-D resistivity at USM
Figure 4.3 2-D resistivity inversion of line LB1-LB3 Sungai Batu Kedah 62
Figure 4.4 2-D resistivity inversion of line LB4-LB7 Sungai Batu Kedah 63
Figure 4.5 Location of map 2-D resistivity, mackintosh probe and 67 Borehole at Sungai Batu Figure 4.6 The correlation between 2-D resistivity inversion of LB1, MP2 68 and BH2 at distance 21.25 m
Figure 4.7 The correlation between 2-D resistivity inversion of LB2, MP3 70 and BH3 at distance 51.25 m
Figure 4.8 The correlation between 2-D resistivity inversion of LB3, MP4 72 and BH4 at distance 151.25 m
Figure 4.9 The correlation between 2-D resistivity inversion of LB4, MP5 74 and BH5 at distance 101.25 m
Figure 4.10 2-D resistivity inversions of survey line L5-LB7 Sungai Batu 76 Kedah
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LIST OF SYMBOLS
A Area
I Current
k Geometric factor
km Kilometer
ℓ Length
m Meter
R Resistance
V Voltage
x Distance
Ωm Ohm-meter
ρ Resistivity
ρa Apparent resistivity
∆V Potential difference
> More than
< Less than
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LIST OF ABBREVIATIONS
BH Borehole
C Current electrode
CPT Cone Penetration Test
ERT Electrical Resistivity Tomography
ES Electrode Selector
LB Lembah Bujang
M M-value
MP Mackintosh Probe
N N-value
P Potential electrode
RMS Root Mean Square
SAS Signal Averaging System
SB Sungai Batu
SPT Standard penetration test
USM University Sains Malaysia
Z Depth
2-D Two Dimension
3-D Three Dimension
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KORELASI ANTARA NILAI SPT, MACKINTOSH PROBE DAN
KEBERINTANGAN 2-D UNTUK KETEKALAN TANIH
ABSTRAK
Kajian menggunakan kaedah geofizik dan geoteknik telah dijalankan untuk
mengkaji ketekalan tanih di USM, Pulau Pinang dengan kawasan granit terluluhawa
dan Sungai Batu, Kedah (Malaysia) dengan kawasan sedimen. Kaedah geofizik yang
digunakan adalah kaedah pengimejal keberintangan 2-D, sementara kaedah
geoteknik digunakan adalah kaedah mackintosh probe dan lubang bor. Terdapat 8
garisan tinjauan keberintangan 2-D, 5 titik mackintosh probe dan 5 lubang bor telah
dijalankan pada dua kawasan tersebut. Data keberintangan 2-D diproses
menggunakan perisian RES2DINV dan Surfer8. Objektif kajian ini adalah untuk
mengetahui ciri-ciri tanih, untuk perbandingan nilai-M dengan nilai keberintangan 2-
D dan untuk mengembangkan jadual nilai-N, nilai-M dan nilai keberintangan 2-D
yang mempunyai hubungan untuk parameter tanih pada kawasan granit terluluhawa
dan sedimen. Model penyongsangan keberintangan 2-D menunjukkan USM, Pulau
Pinang memiliki nilai keberintangan 0-1600 Ωm dengan kedalaman 10 m dan Sungai
Batu, Kedah memiliki nilai keberintangan 0-2000 Ωm dengan kedalaman 40 m.
Hubungkait antara data kerintangan 2-D dengan data mackintosh probe dan lubang bor
menyediakan jenis dan kekuatan tanih untuk kawasan USM, Pulau Pinang dengan kawasan
granit terluluhawa menunjukkan dua jenis tanah lembut; pertama tanih berpasir longgar
dengan nilai-N adalah 8 dan nilai-M adalah 170 yang mempunyai nilai keberintangan adalah
790 Ωm dan yang kedua kelodak berpasir keras dengan nilai-N adalah 9-11 dan nilai-M
adalah 135-270 yang mempunyai nilai keberintangan adalah 415-785 Ωm. Sementara untuk
Sungai Batu dengan kawasan pemendapan menunjukkan jenis tanih lempung
berpasir/lempung yang bersifat setengah keras, keras dan sangat keras. Sifat setengah keras
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dengan nilai-N adalah 6-7 dan nilai-M adalah 7-117 dengan nilai keberintangan adalah 4.5-
12.9 Ωm, sementara sifat keras dengan nilai-N adalah 8-13 dan nilai-M adalah 73-
130 dengan nilai keberintangan adalah 4.7-51 Ωm dan sifat sangat keras dengan
nilai-N adalah 14-20 dan nilai-M adalah 224-360 dengan nilai keberintangan 20-205
Ωm.
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CORRELATION BETWEEN SPT, MACKINTOSH PROBE AND 2-D
RESISTIVITY VALUES FOR SOILS STIFFNESS
ABSTRACT
Study using geophysical and geotechnical methods were conducted to study
soils stiffness at USM, Pulau Pinang with weathered granite and Sungai Batu, Kedah
(Malaysia) with sedimentary areas. Geophysical method applied was 2-D resistivity
imaging while geotechnical methods applied were mackintosh probe and borehole. A
total of 8 2-D resistivity survey lines, 5 points of mackintosh probe and 5 boreholes
were established. The 2-D resistivity data were processed using RES2DINV and
Surfer 8 softwares. The objectives of this study are to characterize soils, to compare
M-value and resistivity values and to develop N-value, M-value and resistivity
values related to soil parameter for weathered granite and sedimentary area. The 2-D
resistivity inversion model shows that the resistivity value of the USM, Pulau Pinang
area is 0-1600 Ωm with penetration depth of 10 m. Sungai Batu area shows
resistivity value of 0-2000 Ωm with penetration depth of 40 m. The integration of 2-
D resistivity data with mackintosh probe and borehole data provide two soil types
and stiffness of weathered granite at USM, Pulau Pinang area; first soil type is loose
sand with N-value of 8 and M-value of 170 with resistivity value of 790 Ωm and the
second type is stiff sandy silt with N-value of 9-11 and M-value of 135-270 and
resistivity value of 415-785 Ωm. While at Sungai Batu with sedimentary area shows
that soil of this survey area is classified as sandy clay/clay with medium stiff, stiff
and very stiff condition. The medium stiff soil shows N-value of 6-7, M-value of 7-
117 and resistivity value of 4.5-12.9 Ωm, while stiff soil gives the N-value of 8-13,
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M-value of 73-130 and resistivity value of 4.7-51 Ωm. Lastly, the very stiff soil has
the N-value of 14-20, M-value of 224-360 and resistivity value of 20-205 Ωm.
1
CHAPTER 1
INRODUCTION
1.0 Background
Malaysia is a developing country with rapid developments in infrastructures
such as houses, buildings, roads, bridges, highways, rail tracks, waste water system
and many other types of public facilities. Infrastructures become a part of our lives
and the investigation of the surrounding environment and economic value are crucial.
Development techniques for infrastructures must be kept at sustainable and
affordable rates. Engineering design plays an important role since most building
structures lie on ground and the load has to be supported by the ground safely upon
construction. Subsurface information is very important for engineering design to
provide knowledge about soil profile such as slopes stability, material
inhomogeneities, subsurface boundaries and other properties of materials (Robert,
2000).
Soil is made up of many compositions such as weathered rock particles,
decayed plant and animal matters. Soil was formed slowly from rocks (the parent
material) which eroded into tiny pieces near the Earth's surface. Soil formation takes
thousands of years to make a thin layer of soil. Every type of soil has different
characteristics like colour, texture, structure, mineral content and the depth variation
(Grim, 1953). Sand is a naturally occurring granular material composed of finely
divided rock and mineral particles. It is defined by size, being finer than gravel and
coarser than silt (Ottawa, 1976). Clay is a fine-grained natural rock or soil material
that is a combination of one or more clay minerals with traces of metal oxides and
2
organic matter. Clays are plastic due to their water content and harden, but brittle and
non–plastic upon drying or firing (Guggenheim and Martin, 1995).
In engineering construction, soil problems often occur during or after
construction. These problems happen as the soil cannot reach a required specification
such as bearing capacity to support super structure above it. The existing soils at a
construction site are not always totally suitable to support structures such as
buildings, bridges, highways, and dams. Hence, if the building is constructed on poor
soil, many problems will occur during and after the construction. The building will
crack because of the settlement of the soil. Therefore, before such contraction are
developed there is the need to understand the subsurface. Various technique can be
used for detailed study of the subsurface such as drilling, pit test, geophysical
methods and more. Nowadays, geophysical methods are well known and applied
worldwide to provide useful and cost-effective information about subsurface features
of interest at required level of spatial resolution and target definition. The methods
are designed to measure specific parameters, with spatial variation within the study
area of interest.
Geophysical methods have been used since nearly 70 years ago and they were
predominantly applied in exploration for natural resources (Sirles, 2006). The
application in near surface studies for engineering purposes such as groundwater
exploration, environmental, geotechnical, and archaeological studies is progressively
increasing. The information obtained from geophysical investigation is used to
determine the important information such as hydrostatigraphic framework, depth to
bedrock, extent of concentrated groundwater contaminant plumes, location of voids,
faults or fractures, and the presence of buried materials, such as steels, drums or
3
tanks (Julian et al., 2012). The common methods employed for engineering and
environmental studies include seismic refraction, seismic reflection, multichannel
analysis of surface waves (MASW), Refraction Micro-Tremor (ReMi), cross-hole
seismic tomography, Ground Penetrating Radar (GPR), Electromagnetic (EM),
electrical resistivity, Induced Polarization (IP), Self Potential (SP), gravity and
magnetic surveys (Anderson, 2006; Wightman et al., 2004).
This study is focusing on 2-D resistivity method for investigating subsurface
geological structure of soft soil. The 2-D resistivity is yet another powerful
geophysical method which uses electrical current that is sent through the ground by a
pair of current electrodes (C1 and C2) and measures the potential difference (∆V)
between potential electrodes (P1 and P2) which is used to calculate apparent
resistivity (ρa) (Loke, 1999). This method is frequently used in evaluation of
aquifers, wells and plumes, environmental aspects of landfills, detection of voids and
boulders, locating fractures/weak zones and determination of depth to bedrock
(Azwin, 2011).
1.1 Problem statements
The use of geophysical method by geotechnical engineers have been
increasing all over the world suitability to study soils properties. 2-D resistivity
method offers a non-destructive and a cost effective way of performing
measurements of geotechnical properties. The principle of 2-D resistivity method
was based on current flow in the subsurface profile by representing the resistivity of
soil material. Howevwe, it is impossible to extract the soil parameters by judging
from soil resistivity alone. The resistivity of soil differs depending on the soil type,
mineralogy of the soil, particle size distribution, index properties, unit weight,
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porosity, degree of saturation and other parameters. Proper understanding on how
resistivity causes variation of these parameters can be helpful for development of the
correlations.
However, 2-D resistivity provides information of subsurface and the resulting
model of 2-D resistivity can provide accurate estimation of depth, thickness and
electrical resistivity of subsurface layers. Limited studies have been conducted to
obtain geotechnical parameters using 2-D resistivity method. Quantification of
geotechnical properties has become an important issue for rigorous use of resistivity
values in engineering applications.
The correlation of different geotechnical properties (SPT and Mackintosh
probe) with 2-D resistivity method will close the gap that currently exists between
geophysical and geotechnical engineering methods. The geotechnical engineers will
be able to interpret the 2-D resistivity data and utilize the information for their
design. Therefore, the development of geotechnical parameters from 2-D resistivity
method make the method more effective for subsurface investigation.
1.2 Research objective
The objectives of this study are:
i. To characterize soil of weathered granite at USM and sedimentary
areas at Sungai Batu.
ii. To compare M-value and resistivity value of the soil types.
iii. To develop N-value, M-value and resistivity values related to soil
parameters.
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1.3 Scope of study
2-D resistivity imaging survey was carried out at Universiti Saints Malaysia
(USM), Pulau Pinang, which is a weathered granite area and Sungai Batu, Kedah
(Malaysia), which is a sedimentary area. The method used for this study were 2-D
resistivity imaging measurement, mackintosh probe and borehole. All the data were
integrated using RES2DINV, Excel and Surfer 8 software to identify the relationship
between resistivity value, SPT (N-value) and number of blow (M-value) for soils at
the study areas.
1.4 Thesis layout
The thesis chapters are organized as followed; Chapter Two discusses
previous studies of geophysical methods using 2-D resistivity and geotechnical
methods to understand soils.
Chapter Three contains a detailed description of the study area, research
materials and methodology developed in this study. This chapter also describes
briefly on data acquisition process in all the study areas involved in this research.
Chapter Four discusses all results obtained from borehole data, 2-D resistivity
imaging and mackintosh probe. The chapter also discusses the correlation between
geotechnical and geophysical methods.
Finally, Chapter Five includes the summary regarding the accomplishement
of the work and the conclusion. Recommendations for future research are also
presented in this chapter. Lastly, the list of references, appendices and publications
are attached.
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CHAPTER 2
LITERATURE REVIEW
2.0 Introduction
Basic soil engineering study is defined as the uncemented aggregate of
mineral grains and decayed organic matter (solid particles) with liquid and gas in the
empty spaces between the solid particles. Soil is used as construction material in
various civil engineering projects and it supports structural foundations. Thus, the
study of soil properties, such as its origin, grain-size distribution, water draining
ablility, compressibility, shear strength and load-bearing capacity is vital (Das,
2005).
Soil mechanics is a branch of engineering mechanics that describes the
behaviour of soils. Soil mechanics provide the theoretical basis for analysis in
geotechnical engineering (Osano, 2012). In-situ behaviour of soils is complex
because it is highly dependent upon numerous factors. To acquire appropriate
understanding, it is necessary to analyze them not only through geophysics and
geotechnical engineering skills, but also through other associated disciplines such as
geology, geomorphology, climatology and other earth and atmosphere related to
sciences (Bery and Saad, 2012).
2.1. Borehole method
Borehole is used to identify detailed changes of soil/rock types. The local
variations indicated that borehole data alone could not define the problem
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sufficiently. The characteristic of the area between holes could only be determined
by ground geophysical profiles. This combination proves to be an important and
effective approach for detecting and verifying new impact structures, and it is
essential for detecting and exploring buried ones (Jeffrey, 1999). Figure 2.1 shows
two types of boring method that were used for this study which is wash boring and
rotary drilling. Well bores are generally drilled by circulating a fresh-water
suspension down through the drill pipe and back to the surface through the annular
region between the drill pipe and the rock (Telford, 1990).
Figure 2.1: Types of the boreholes (Hvorsles, 1948).
Standard penetration test (SPT) is carried out in the boreholes and widely
used throughout the world which serves as an indicator for the compressibility and
density of granular soils. It is also commonly used to check the consistency of stiff or
stony cohesive soil and weak rocks. The SPT is carried out at every 0.75 m vertical
Wash boring Rotary drilling
Rope
Derrick Pressure water
Casing Drill rod
Chopping bit
Driving shoe Water jet at high velocity
Rotary hose
Standpip
Mud return line
Mud pid Shale shaker
Annulus
Drill
Drill pipe
Mud pump Kelly
Swivel
8
intervals in a borehole and it can be increased to 1.5 m. Furthermore, N-value is a
number of blows required to achieve a penetration for each 0.75 m that measure the
firmness or density of foundation material.
2.2 2-D resistivity method
2-D resistivity surveys have been used for many decades in hydrogeological,
mining and geotechnical investigations. More recently, it has been used for
environmental surveys. The purpose of 2-D resistivity survey is to determine the
subsurface resistivity distribution by making measurements on the ground surface.
From these measurements, true resistivity (ρ) of subsurface can be estimated. True
resistivity (ρ) is related to various geological parameters such as mineral and fluid
content, porosity and degree of water saturation in the soil/rock (Loke, 1999).
The basic principle of electrical resistivity method is the measurement of a
materials behaviour to retard the flow of electrical current (I) or resistance (R) to the
movement of charge (Awang et al., 2008). The resistivity measurements are
normally made by injecting current (I) into the ground and meansuring the value of
potential difference (V) (Loke, 1999). Electrical resistance measurement according to
Ohm’s Law is given by (Equation 2.1);
(2.1)
Where;
R: Resistance of the conductor.
The SI unit for resistance is volts per ampere or Ohm (Ω). The resistivity can
be calculated as (Equation 2.2);
IV
=R
9
(2.2)
Where;
ρ: Resistivity of the conductor material (Ωm)
L: Length of the conductor (m)
A: Cross-sectional area (m2)
For a homogeneous medium (Figure 2.2), the resistivity measurements are
normally made by injecting current into the ground through two current electrodes
(C1 and C2), and measuring the resulting voltage difference at two potential
electrodes (P1 and P2). From the current (I) and voltage (V) values, an apparent
resistivity (ρa) value is calculated (Equation 2.3).
Figure 2.2: Four electrodes array for subsurface resistivity measurement.
(2.3)
Where;
k : geometric factor which depends on the arrangement of the
four electrodes.
Resistivity meter normally provides a resistance value (R), so in practice the
apparent resistivity value is calculated by (Equation 2.4);
(2.4)
P2 C2 P1 C1
Ground
AL
ρ=R
IV
k=ρa
kR=ρa
10
The calculated resistivity value is not the true resistivity of the subsurface, but
an apparent value which is the resistivity of a homogeneous ground which will give
the same resistance value for the same electrode arrangement. The relationship
between apparent resistivity and true resistivity is a complex relationship. To
determine the true subsurface resistivity, an inversion of the measured apparent
resistivity values using a computer program must be carried out (Loke, 1999; 2004).
2.2.1 2-D resistivity imaging
2-D resistivity imaging is a model of resistivity changes in vertical and
horizontal direction. The technique assumed that resistivity does not change in the
direction that is perpendicular to the survey line. It provides useful result besides
being the most practical and economic compromise between providing an accurate
result in many geological situations (Loke, 1999). However, typical 1-D resistivity
sounding surveys is usually involve about 10-20 readings, while 2-D resistivity
imaging surveys involve about 100-1000 measurements. For wider study area, the
survey usually carried out in larger number of electrodes, 25 or more and connected
to multi-core cable. The multi-core cable is then connected to an automated computer
operated switch box known as electronic switching (Figure 2.3) to select the four
electrodes to be used (C1, C2, P1, P2).
11
Figure 2.3: The arrangement of electrode for 2-D resistivity imaging survey and the sequence of measurements used to build up the resistivity section (Loke, 1999). 2.2.2 Arrays
Choosing the best array for a field survey depends on the type of structure to
be mapped, sensitivity of the resistivity meter and background noise level. In
practice, the arrays that are most commonly used for 2-D resistivity imaging surveys
are Wenner, Dipole-dipole, Wenner-Schlumberger, Pole-pole and Pole-dipole.
Among the characteristics of an array that should be considered are sensitivity of the
array to vertical and horizontal changes towards subsurface resistivity, depth of
investigation, horizontal data coverage and signal strength (ABEM, 2006). Figure 2.4
shows the common arrays used for 2-D resistivity survey with their geometric factor,
k.
56 n = 6
Station 32
Station 18
Station
C1
C1
C1
C2
C
C2
P1
P1
P
P2
P2
P
3a 3a 3a
2a 2
2a
a a a 1 2 3 4 5 6 7 8 9 10 11 12 13 1
15 16 17 18 19 20
Electrode number
Resistivity meter Laptop computer
1
18
32
43 51
Data
n = 1 n = 2 n = 3 n = 4 n = 5
12
Figure 2.4: Common resistivity array and their geometric factors ( Loke and Barker, 1996).
Pole-dipole array uses four electrodes, two potential electrodes (P1 & P2) and
two current electrodes (C1 & C2), “a” is the spacing between P1 and P2 which move
along the survey line for “n” spacing from current electrode C1. The C2 electrode
acts as a remote electrode which must be placed sufficiently far from the survey line.
The sufficient electrode effect can be stated as approximately proportional to square
of ratio distance between C1-P1 and C2-P1. Pole-dipole array is not as sensitive to
telluric noise as the Pole-pole array. This array also has relatively good horizontal
coverage, but it has a significantly higher signal strength compared to Dipole-dipole
array. Pole-dipole array is an asymmetrical array which produces asymmetrical
apparent resistivity anomaly in resistivity section. To eliminate the effect of
P2
C1
a a a
Wenner Gamma C1 P1 C2 P2
k = 3πa
a
Pole - pole C1 P1
k = 2πa
a
Dipole - dipole
a na C2 C1 P1 P2
k = πn (n + 1) (n + 2) a
Pole - dipole
na a C1 P1 P2
k = 2πn (n + 1) a
k = 2π bL / (L - b)
b = na
L = [(a*a) + (b*b)] 0.5 k = geometric factor
Wenner Schlumberger
P1 P2 C2 na na a
k = πn (n + 1) a
Equatorial Dipole - dipole
na b
a a
C1 P1
C2 P2
C1 Wenner Alpha Wenner Beta
P1 P2 C2 a a a
k = 2πa
C2 C1 P1 a a a
k = 6πa
13
asymmetry resistivity section, measurements were repeated with the electrodes
arranged in reverse manner and combining the forward and reverse measurements to
produce a final section (Figure 2.5).
Figure 2.5: Forward and reverse Pole-dipole array (Loke, 1999).
2.2.3 Resistivity of rock and minerals
Rock and minerals have their own electrical conductivity and resistivity
values. The same rock and minerals do not necessarily have the same resistivity
values because different rocks may have the same resistivity value. This occurs
because the value of the resistivity of rock and minerals has a range of values that
can overlap. The electrical properties of the rocks are characteristics of rocks when
electric current flows into it. This electric current can be derived from nature itself or
due to an imbalance of electrical current that deliberately put into it.
Generally resistivity values of soil/rock depend on various numbers of
physical parameters such as porosity, salinity, temperature, rock conductivity and
thermal changes. In other words, porosity and saturation of the fluid tend to be
dominant in resistivity measurements (Reynolds, 1997). Table 2.1 shows the
resistivity values of some common minerals and rocks.
C1 P1 P2 na a
C1 P1 P2 a na
Forward
Pole-dipole
Reverse
Pole-dipole
14
Table 2.1: Resistivity value of some common materials and rocks (Reynolds, 1997)
Rock /soils type Resistivity (Ωm) Granite 3 x 102 - 106
Granite (weathered) 3 x 10 – 5 x 102
Schist (calcareous and mica) 20 - 104
Schist (graphite) 10 x 102
Sandstones 1 – 7.4 x 108
Limestone 50 - 107
Clays 1 x 102
Alluvium and sand 10 – 8 x 102
Consolidated shale 20 – 2 x 103
Sand and gravel 30 – 225
2.3 Mackintosh probe
Dynamic probing test using mackintosh probe (MP) is a continuous soil
investigation technique, which is one of the simplest soil penetration tests. It
basically consists of a metal tipped probe which is repeatedly driven into the ground
using a drop weight of fixed mass. Testing is carried out continuously from ground
level to the final penetration depth. The continuous sounding profiles enable easy
recognition of dissimilar layers and thin strata by the observed variation in the
penetration resistance. Figure 2.6 illustrate the mackintosh probe equipment. The
mackintosh probe (MP) is a light weight dynamic penetrometer and a considerably
faster and cheaper tool than boring, particularly when the depth of exploration is
moderate and the soils being investigated are soft or loose (Sabtan and Shehata,
1994). The method can be used in difficult terrain such as swampy ground (Kong,
1983). Mackintosh probe test is most widely used in in-situ tests to measure the soil
15
bearing capacity of different layers in terms of M-value. This test is very useful to
find out the bearing capacity of soil up to 15 m depth.
Figure 2.6: The illustration of mackintosh equipment (Fakhrer et al., 2006).
2.4 Previous study
Previously, there are many researchers discussing soils in engineering
perspective. Ayob et al. (2015) studied the effects of penetration rate on the
penetration resistance using Cone Penetration Test (CPT). The research was
conducted at RECESS UTHM and CPT was used in three selected ranges; 0.5 cm/s,
1 cm/s and 5 cm/s. In addition, Mackintosh probe (MP) test has been considered as a
comparison with CPT test for the unconfined compressive strength. The results show
that the different penetration rate was influenced by the soil shear strength. It was
found that the cone resistance increased when higher speed of soundings performed
for the CPT. For the slowest rate (0.5 cm/s), the shear strength is approximately
0.15% less compared to the standard rate (2 cm/s). However, the highest rate (5
cm/s), the shear strength was 0.22% more than the reference rate (0.5 cm/s). In
4.5 Kg Drop hammer
Coupling
Boring rods
Cone
16
comparison, the soil strength from Mackintosh probe was lower than the CPT data.
The mackintosh probe record show M-value increases with increasing depth (Figure
2.7).
Figure 2.7: Soil strength based on mackintosh probe test (Ayob et al.,2005).
Tarawneh (2014) studied about the correlation between Standard Penetration
Test (SPT) and Cone Penetration Test (CPT) for sand, silty sand and sandy silt soil.
The study was conducted in Dubai, UAE. In this study, multiple linear regression
(MLR) and symbolic regression (SR) were used to develop formulae that can predict
N-value using CPT data for sand, sandy silt and silty sand soils samples. Data used in
this study consist of 66 CPT-SPT pairs of sand, sandy silt and silty sand soils.
Distance between each CPT-SPT pairs ranged from 3-40 m. The depth of the SPT-
CPT pairs ranged from 3-9 m. It was concluded that SR showed some improvement
to the developed MLR model and those developed models can be used to predict N-
value from CPT data with acceptable accuracy.
Electrical Resistivity Tomography (ERT), Standard Penetration Test (SPT)
and Dynamic Cone Penetration Test (DCPT) investigations have been carried out for
thermal power plants at Aligarh and Jhansi sites (India). Two ERT profiles with 355
m long, 72 electrodes planted with 5 m interval. ERT of the two sites are presented in
Figure 2.8.
b) Strength (MPa) a) Strength (MPa) c) Strength (MPa)
Dep
th (m
)
Dep
th (m
)
Dep
th (m
)
17
(a) Aligarh
(b) Jhansi
Figure 2.8: Resistivity imaging of (a) Aligarh and (b) Jhansi (Sudha et al., 2008).
Resistivity image of Aligarh and Jhansi showed high resistivity near the
surface. High resistivity was characterized by the presence of boulder close to the
surface. The low resistivity zone was reported due to the existence of fine soils in
Jhansi. Obtained SPT values were plotted with resistivity at the borehole location as
shown in Figure 2.9.
18
Figure 2.9: SPT value vs resistivity plot (Sudha et al., 2008).
Figure 2.9 showed no specific correlations between SPT and resistivity.
However, linear correlation was observed when SPT values were plotted with
transverse resistance as presented in Figure 2.10.
Figure 2.10: SPT vs transverse resistivity of two locations Aligarh and Jhansi (Sudha et al., 2008).
The authors concluded that the correlation of SPT with transverse resistivity
was site specific and solely dependent on the geologic environment of the study
period. The study illustrate the effectiveness of correlating geophysical method in
Aligarh Jhansi
Resistivity (Ωm)
Ave
rage
N-v
alue
19
geotechnical perspective which will lead to time and cost effective compared to only
geotechnical method conducted at the area (Sudha et al., 2008).
A research was conducted at Magodo Phase II Lagos in Nigeria to study
subsoil investigations using 2-D resistivity for geophysical method and Cone
Penetration Test (CPT) for geotechnical method. The results show that this research
consists of four soils types; Top soil with the resistivity value of 86-386 Ωm and
depth 0.53-1.07 m, sandy clay and sand with resistivity value of 227-602 Ωm and 95-
262 Ωm with a depth of 5.49 m and 14.33-37.3 m for sand respectively. While the
clay was identified with thickness of 27.6-55.9 m and resistivity value of 110-342
Ωm. CPT shows competent values for penetrative resistance at 14-18 m. The study
shows that shallow foundation was feasible in some part of the study area and the
two methods correlate well with each other (Oyedele and Okoh, 2011).
Abidin et al. (2012) conducted a study at Kuala Lipis (Pahang) and Tanjung
Malim (Perak) Malaysia to evaluate some relation between near surface ground
stiffness status with integrated of geophysical and geotechnical method. This study
also investigates the stability of slope with effect of heterogeneous subsurface in
tropical region with 2-D resistivity and geotechnical SPT (N-value). Figure 2.11 (a)
and (b) showed result of Kuala Lipis and Tanjung Malim respectively.
20
(a) Kuala Lipis
(a) Tanjung Malim
Figure 2.11: 2-D resistivity subsurface profile image obtained from geoeletrical survey (Abidin et al., 2012).
The results induced that a linear relationship between the parameters of high
resistivity values will generate high stiffness for higher N-value. In contrast, the
decrease in observed low resistivity did not decrease the N-value (Figure 2.12 and
Figure 2.13).
Ωm
Ωm