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Application of Piezoelectric Sensors in Soil Property Determination 39 APPLICATION OF PIEZOELECTRIC SENSORS IN SOIL PROPERTY DETERMINATION by LEI FU Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Dissertation Advisor: Prof. XIANGWU ZENG Department of Civil Engineering CASE WESTERN RESERVE UNIVERSITY August, 2004 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the dissertation of ______________________________________________________ candidate for the Ph.D. degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. DEDICATION To my parents To my wife, Xiaoli To my daughter, Katherine I love you all TABLE OF CONTENTS TABLE OF CONTENTS i LIST OF TABLES iv LIST OF FIGURES vi ACKNOWLEDGEMENTS xi ABSTRACT xii CHAPTER 1 INTRODUCTION 1 1.1 Introduction 1 1.2 Laboratory Measurement of Soil Properties 1 1.2.1 Introduction 1 1.2.2 Element Tests 3 1.2.3 Model Tests 5 1.2.4 Centrifuge Tests 7 1.2.4.1 Introduction 7 1.2.4.2 Scaling Laws 9 1.2.4.3 Limitations of Centrifuge Modeling 12 1.2.4.4 CWRU Centrifuge 16 1.3 Field Determination of Soil Properties 22 1.3.1 Introduction 22 1.3.2 Seismic Methods 23 1.3.2.1 Crosshole Method 24 1.3.2.2 Downhole Method 26 1.3.2.3 Shear Wave Refraction Method 27 1.3.2.4 SASW Method 28 1.3.3 Cone Penetration Tests (CPT) 29 1.3.4 Standard Penetration Tests (SPT) 30 1.4 Piezoelectric Sensors and Their Applications 31 1.4.1 Introduction 31 1.4.2 Piezo Motors 33 1.4.3 Piezo Generators 34 1.4.4 2-Layer Elements 34 1.4.4.1 Bender Elements 34 1.4.4.2 Extender Elements 37 1.1.1 Series and Parallel Operation 37 1.1.2 Application of Piezoelectric Sensors in Soil Property Determination 39 i CHAPTER 2 LITERATURE REVIEW 41 2.1 Review of Piezoelectric Sensors in Soil Property Measurement 41 2.2 Review of Soil Property Measurement in Centrifuge tests 44 2.3 Research Objectives and Outline 52 2.3.1 Research Objectives 52 2.3.2 Outline 53 CHAPTER 3 BENDDER ELEMENTS IN CENTRIFUGE MODEL TESTS ---DRY SPECIMEN TESTS 54 3.1 Introduction 54 3.2 Bender Elements 55 3.3 Nevada Sand 56 3.4 Experimental Setup 58 3.5 Description of the Model 61 3.6 Model preparation 63 3.7 Test Procedures 66 3.8 Experimental Results and Analysis 66 3.9 Conclusions 79 CHAPTER 4 BENDER ELEMENTS IN CENTRIFTGUE MODEL TESTS ---SATURATED SPECIMEN TESTS 80 4.1 Introduction 80 4.1.1 Evaluation Liquefaction Potential of Soils 80 4.1.2 Content of This Chapter 86 4.2 Test Equipment 86 4.3 Input Earthquake Motion 86 4.4 Transducer Description 87 4.4.1 Water-proof Bender Elements 87 4.4.2 Accelerometers 88 4.4.3 Pore Pressure Transducers 88 4.5 Preparation of Saturated Models 90 4.5.1 Description of the Models 90 4.5.2 Preparation of the Models 92 4.5.3 Pore Fluid 95 4.5.4 Saturation of specimen 97 4.6 Centrifuge Testing Procedure 98 4.7 Test Results 101 4.7.1 Shear Wave Velocities 101 4.7.2 Pore Pressures 106 4.7.3 Accelerations 106 ii 4.7.4 Examination of Liquefaction Criteria Based on Shear Wave Velocities 107 4.8 Conclusions 116 CHAPTER 5 PIEZO CONE PENETROMETER 118 5.1 Introduction 118 5.2 Piezo Cone Penetrometer Structure 119 5.3 Experimental setup 123 5.4 Principle of the Tests 125 5.5 Field Test Procedure 126 5.6 Typical Laboratory Test Results 127 5.6.1 Soil Description 127 5.6.2 Test Procedure 128 5.6.3 Test Results 128 5.7 Conclusions 135 CHAPTER 6 ODOMETER FOR GRAVELLY MATERIAL STIFFNESS MEASUREMENTS 136 6.1 Introduction 136 6.2 Equipment Description 140 6.3 Experimental Setup 143 6.4 Typical Test Results 144 6.4.1 Soil Description 144 6.4.2 Test Procedures 145 6.4.3 Test Results 145 6.5 Conclusions 148 CHAPTER 7 SUMMARY OF CONCLUSIONS AND SUGGESTIONS FOR FUTURE STUDY 149 7.1 Introduction 149 7.2 Summary of Observations and Conclusions 151 7.2.1 Application of Bender Elements in Centrifuge Tests 151 7.2.2 Piezo Cone Penetration for Pavement Field Tests 153 7.2.3 Odometer for Gravelly Material Stiffness Measurements 154 7.3 Suggestions for Future Study 155 REFERENCES 159 iii LIST OF TABLES Table 1.1 Relative Quality of the Laboratory Technique for Measurement of Dynamic Soil Properties (after Silver, 1981) 4 Table 1.2 Scaling Factors for Centrifuge Tests (after Taylor, 1995) 12 Table 1.3 Comparison of Methods for Centrifuge Earthquake Motion Simulation (after Whitman, 1988) 18 Table 3.1 Bender Element Performance (Source: Piezo Systems, Inc.) 56 Table 3.2 Index Properties of Nevada Sand (after Arulmoli, 1994) 57 Table 3.3 Locations of the Bender Elements in Models 62 Table 3.4 Shear Save Velocities Measured during Spin-up of the Centrifuge (Dr = 30%) 68 Table 3.5 Shear Wave Velocities Measured during Spin-up of the Centrifuge (Dr = 48%) 69 Table 4.1 Specifications of Accelerometer 89 Table 4.2 Calibrations of Accelerometers 89 Table 4.3 Specifications of Pore Pressure Transducers 90 Table 4.4 Calibrations of Pore Pressures Transducers 90 Table 4.5 Locations of Sensors 92 Table 4.6 Physical Properties of METHOCEL (Source: Dow Chemical Company) 96 Table 4.7 Shear Wave Traveling Time 102 Table 4.8 Shear Wave Velocities (Spin-up) 102 Table 4.9 Shear Wave Velocities (after the First Earthquake) 103 Table 4.10 Shear Wave Velocities (after the Second Earthquake) 103 iv Table 5.1 Types of the Elements 120 Table 5.2 Index Properties of Two Soils 127 Table 5.3 Test Results on Nevada Sand 130 Table 5.4 Test Result on Delaware Clay 130 Table 5.5 Summary of the Results of CBR Tests 134 v LIST OF FIGURES Figure 1.1 Range and Applicability of Dynamic Laboratory Tests (after Das, 1993) 4 Figure 1.2 Sketch of the Mechanics Relating to the Two Types of Centrifuges 6 Figure 1.3 Takenaka Corporation Centrifuge (Source: Takenaka Corporation) 8 Figure 1.4 Stresses in Model and Prototype 10 Figure 1.5 Stress Variation with Depth in a Centrifuge Model (after Taylor, 1995) 14 Figure 1.6 CWRU Laminar Box (after Dief, 2000) 21 Figure 1.7 Crosshole Method 25 Figure 1.8 Downhole Method 26 Figure 1.9 Shear Wave Refraction Method 27 Figure 1.10 Spectral-Analysis-of-Surface-Waves Method 29 Figure 1.11 Sketch of a Cone Penetrometer 30 Figure 1.12 SPT Test (after Kovacs et al., 1981) 31 Figure 1.13 Peizoceremic Material 32 Figure 1.14 Sketch of a Motor 33 Figure 1.15 Sketch of a Generator 34 Figure 1.16 Structure of a 2-Layer Piezo Element 35 Figure 1.17 Bender Element Transmitter 36 Figure 1.18 Bender Element Generator 36 Figure 1.19 A 2-Layer Bender Element Poled for Series Operation 38 vi Figure 1.20 A 2-Layer Bender Element Poled for Parallel Operation 38 Figure 1.21 Setup for Incorporating Bender Elements in the Resonant Column Apparatus (after Dyvik, 1985) 40 Figure 2.1 Experimental System (after Shibata et al., 1991) 48 Figure 2.2 Layout of Bender Source and Receiver (after Gohal and Finn, 1991) 49 Figure 2.3 In-Flight Shear Wave Measurement (after Arulnathan et al., 2000) 51 Figure 3.1 Dimension of the Bender Element 55 Figure 3.2 Grain Size Distribution of Nevada Sand 57 Figure 3.3 Experimental Setup 60 Figure 3.4 Test Equipment in Laminar Box 60 Figure 3.5 Bender Elements in Soil Model 61 Figure 3.6 Traveling Pluviation Apparatus 65 Figure 3.7 Typical Recorded Signal 67 Figure 3.8 Effect of Relative Density on Shear Wave Velocity Measured during Spin-up of the Centrifuge 70 Figure 3.9 Repeatability of Shear Modulus Determined during Spin-up of Two Different Centrifuge Models 71 Figure 3.10 Change of Shear Save Velocity with Acceleration during Spin-up of the Centrifuge 71 Figure 3.11 Comparison between Test Results and Results from Empirical Equation 74 Figure 3.12 Shear Modulus during Spin-up and Spin-down of the Centrifuge 75 Figure 3.13 Comparison of Gmax by Resonant Column Tests and Bender Element Tests during Spin-up of the Centrifuge (Dr = 30%) 77 Figure 3.14 Time History of Base Acceleration Scaled to Prototype Values 77 vii Figure 3.15 Effect of Earthquake Shaking on Shear Modulus Measured during Spin-down of the Centrifuge 78 Figure 4.1 Relationship between Cyclic Stress Ratios Causing Liquefaction and (N1)60 Values (after Seed et al., 1975) 84 Figure 4.2 Liquefaction Relationship Recommended for Clean, Uncemented Soils (after Andrus and Stoloe, 2000) 85 Figure 4.3 Prototype Acceleration of Base Input Motion 87 Figure 4.4 Locations of Sensors in Centrifuge Model 91 Figure 4.5 Schematic of the Chamber with an Air Tight Lid (after Dief, 2000) 94 Figure 4.6 Effect of Pore Fluid Viscosity on Pore Pressures in Centrifuge Model Tests (after Dief, 2000) 96 Figure 4.7 Model Saturation System (after Dief, 2000) 98 Figure 4.8 Shear Wave Velocity Vs Acceleration (Spin-up, before Earthquake) 104 Figure 4.9 Variations of Shear Wave Velocity with Depth in the Model (Spin-up, before Earthquake) 104 Figure 4.10 Shear Wave Velocities before and after the First Earthquake 105 Figure 4.11 Comparison of Shear Wave Velocities after the First and Second Earthquakes 105 Figure 4.12 Pore Pressure History of the Top Point during the First Earthquake 109 Figure 4.13 Pore Pressure History of the Middle Point during the First Earthquake 109 Figure 4.14 Pore Pressure History of the Bottom Point during the First Earthquake 110 Figure 4.15 Pore Pressure History of the Top Point during the Repeated Earthquake 110 viii Figure 4.16 Pore Pressure History of the Middle Point during the Repeated
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