UNIVERSITI TEKNOLOGI MARA
GEORESISTIVITY INDEX OF COMPOSITE GEOSTRATA AT DIFFERENT CONDITIONS
NOORASYIKIN MOHAMMAD NOH
Thesis submitted in fulfillment of the requirements for the degree of
Master of Science
Faculty of Civil Engineering
March 2011
ABSTRACT
A geotechnical engineering exploration begins with a site investigation of the subsurface to determine the ground stabilization for the proposed construction. There are two types of techniques that have been used widely in site investigation;
destructive techniques for examples testing material from samples extracted through the drilling method and non-destructive techniques for example the resistivity method. The conventional destructive techniques have the disadvantages of sampling disturbance that would affect the data accuracy because of disturbance and contaminant. For non-destructive technique, it is known to be optimum, insitu condition and higher accuracy of data. In this study, a non-destructive innovative laboratory technique of georesistivity technique has been developed for geocharacterization of laboratory scale material and georesistivity tank modeling with stratified materials. The main objectives of this study are to determine the physical properties and georesistivity index of geomaterials, to determine the 2D georesistivity profiling of stratified soil and hard layer, and to correlate the georesistivity index with physical properties of materials. It is found that the resistivity of geological samples depends on several factors. These include the amount of water present in the pores and its porosity. The dominant factors that typically determine a sample's resistivity are the amount of the fluid as conductor where dry material will be more resistive than wet material. From the pilot study, it is found that the presence of clay minerals, such as montmorillonite, results in low resistivity and the materials contains water soluble minerals, such as salt, also result in a low resistivity from the addition of water. Generally, in scientific fundamental every mineral has its own resistivity index. Chemical reactions involving different mineral phases of the sample may also affect its resistivity. If the samples contain significant concentrations of interconnected metallic minerals, such as pyrite, a low resistivity may be observed. For sulfide minerals, it produces dissolved iron and sulfate ions when it reacts with water that increases the conductivity of the fluid.
Two types of samples have been tested in this study; cement mortar and soil samples.
From the results obtained, it can be found that the most minerals composite in the soil samples are clay minerals such as muscovite and nacrite. Based on the pilot study, the clay minerals would give low resistivity value because this mineral can absorb water easily. The others results are resistivity which resistivity value decreases when the values of moisture content and porosity are increases. Tank modeling with stratified soils and hard layer were the second stage of this study.
Resistivity survey was conducted with cement mortar which represent hard layer, different layers of soil with different thickness and percentage of moisture content.
The minimum electrode spacing that was applied in this test is 0.04m and the size of tank that was used is 183cmLx39cmWxl50cmH. The results were interpreted by using Res2DINV software where the images of the subsurface for the different materials were derived. Based on the results obtained, the results of georesistivity index are mainly depending on moisture content that filled in the pore space and composition of clay mineral that affects to the soil mass.
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ACKNOWLEDGEMENTS
Foremost, I would like to praise to all the important people who have been involved in this research Master. Thanks to my parents Ir.Mohammad Noh Bin Tarkib and Roslilawaty Binti Ismail for giving me endless support, help and encouragement in the completion of this project. Thanks also to my siblings for their supporting. I wish to thanks very much to my project supervisor Prof.Ir.Dr.Zainab Mohamed for her supervising and guidance in the process of making this report highly appreciated.
It is never complete without wishing a deepest thanks to Dr.Kamaruzzaman, Dr.Haryati Awang, Mr.Muhammad Azahar Abdul Razak, and Mr.Mohd Ismail Mohd Mazlan for then- helping directly or indirectly in completion of this thesis.
Finally, I would like to express my greatest appreciation to Dr.Nawawi, Dr.Shamsudin, and Mr.Ahmad and my friends for encouragement and support during the project period when conducting this research Master.
TABLE OF CONTENTS
Page
DECLARATION ii ABSTRACT iii ACKNOWLEDGEMENT iv
CONTENTS v LIST OF TABLES viii LIST OF FIGURES ix
CHAPTER I: INTRODUCTION
1.0 Introduction 1 1.1 Problem Statement 2
1.2 Objectives 3 1.3 Significance of the Research 3
1.4 Limitation of Study 3 1.5 Thesis Outline 4
CHAPTER 2: LITERATURE REVIEW
2.1 Geophysical Technique 5 2.2 Georesistivity Technique 8
2.2.1 Theoretical Background 11 2.2.2 Types of Georesistivity Surveys 13
2.2.2.1 Root Mean Square Error (RMSE) 16
2.2.3 Onsite Survey Concern 17 2.3 Electrical Resistivity Protocol Types 17
2.3.1 Types of Protocol 17 2.3.2 Comparative Advantages and Disadvantages 18
2.3.3 Limitation of Each Protocol 19 2.3.4 Ratio between Depth of Image and Electrode Spacing For Each 20
Protocol
2.4 Georesistivity Index of Geomaterials 22 2.4.1 Classification of Materials According To Georesistivity Index 23
2.4.2 Previous Studies 26
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CHAPTER 3: RESEARCH METHODOLOGY
3.1 Introduction 34 3.2 Sample Preparation 37
3.2.1 Cement Mortar Samples 37
3.2.2 Soil Samples 38 3.3 Physical Properties of Cement Mortar and Soil Samples 39
3.3.1 Moisture Content 39 3.3.2 Soil Classification 40 3.3.3 Soil Mineralogy 41 3.3.4 Petrographic Study of Cement Mortar 42
3.4 Georesistivity Index Test 44 3.4.1 Georesistivity Index for Geomaterial Scale 44
3.5 Laboratory Model Study of the Georesistivity of the Interbedded 45 Strata
3.5.1 Model 1 45 3.5.2 Model 2 47 3.5.3 Model 3 47 3.5.4 Model 4 58 CHAPTER 4: RESULTS AND DISCUSSION
4.1 Introduction 52 4.2 Physical Properties of samples 52
4.2.1 Soil Classification 52 4.2.2 Mineralogy of the soil 53 4.2.3 Texture of Cement Mortar 54 4.3 Georesistivity Index Test of Cement Mortar and Soil Samples 55
4.4 Georesistivity of Composite Strata - Laboratory Model Study 59
4.4.1 Model 1 - Dry Condition 59 4.4.2 Model 2 - Geostrata at Wet and Undrained Condition 59
4.4.2.1 Verification of Georesistivity Value of Cement 67 Mortar and Sandy Soil Sample using Multimeter
4.4.3 Model 3 - Undrained and Drained Condition 68 4.4.3.1 Comparative Study of the Model 3 at Drained and 72
Undrained Conditions
4.4.4 Model 4 - Effect of Surcharge Load 76 4.4.5 Summary of Georesistivity Index and Moisture Content 79
For Model 1, Model 2, Model 3, and Model 4
4.46 Relationship of Sandy Soil Material to Sandy Soils Masses 85
