EFFECT OF DEFORMATION OF PREFABRICATED VERTICAL DRAINS (PVD) ON DISCHARGE CAPACITY and THE CHARACTERISTICS OF PVD SMEAR ZONE by Hoang-Hung Tran-Nguyen A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Civil and Environmental Engineering) at the UNIVERSITY OF WISCONSIN-MADISON 2010 © Copyright by Hoang-Hung Tran-Nguyen 2010 All Rights Reserved ABSTRACT EFFECT OF DEFORMATION OF PREFABRICATED VERTICAL DRAINS (PVD) ON DISCHARGE CAPACITY AND THE CHARACTERISTICS OF PVD SMEAR ZONE Hoang-Hung Tran-Nguyen Under the supervision of Professor Tuncer B. Edil At the University of Wisconsin-Madison This study investigates the discharge capacity behavior of deformed PVDs using laboratory performance tests. A PVD-Soil (PVD-S) model test apparatus is developed. Four different PVDs were tested and two different soils were used for confinement.
Deformation of PVDs causes a significant reduction in discharge capacity. The discharge capacity reduced up to 99% at maximum settlement of 41% for a PVD. The hydraulic gradient also appreciably affects discharge capacity due to non-laminar flow in the core of the PVD. Soil type impacts the deformation pattern of PVDs, but minimal effect on discharge capacity in this study.
Soil type, however, has a significant influence on required discharge capacity. Due to short drain length, the discharge capacity of any of the PVDs tested in this study was sufficient for consolidation settlements up to 40%. The study attempts to determine the extent of the smear zone and to measure the hydraulic conductivity of the smear zone directly by laboratory tests. A Smear Zone Model (SZM) test is developed.
Two successful tests were conducted, one on Kaolinite clay and another on Craney Island dredgings, to determine the characteristics of the smear zone. The excess pore water pressure generated in the soil adjacent to the PVD reaches the highest and the lowest values during the pushing in and the pulling out of i ACKNOWLEDGEMENT I would like to express my deep gratitude to Professor Tuncer B. Edil, my advisor, for his instruction, mentorship, and thoughtfulness throughout my doctoral study at the University of Wisconsin-Madison. I would not be at the University of Wisconsin-Madison without his generous support.
I am grateful Professor James Schneider for his effort to help me apply my experimental models on a real project, dredgings improvement using PVD in Craney Island, Virginia. I gratefully acknowledge his effort in my PVD deformation study. I also greatly thank Professor Dante Fratta for his willingness and encouragement to guide me to apply geophysical methods such as TDR and Bender Element in my study. I would like to thank Professor James Tinjum for serving on my committee, reviewing the manuscript, and giving thoughtful and invaluable comments.
I also would like to give thanks for Professor Chin Wu for serving on my committee. I would like to thanks Mr. Xiaodong Wang, laboratory manager, who gave me priceless help, assistance, and technical advice during development and operation of the experimental devices over four years. I am grateful Mr.
William Lang, laboratory manager who helps me use equipment in the Structure Laboratory. I also highly appreciate Geo fellows for their kindness and willingness to help me in different ways. They contributed to my unforgettable memories of school-time in Madison. I am grateful Professor Judith Ladinsky (International Health, Medical School) and her assistant, Dr.
Nancy Volk, for their endless support from the first day at the UW-Madison. I also express my thanks to the Vietnamese student community for their exceptional support from my first day in the United State of America. I would like to thank my family and my friends in Vietnam who continuously support and encourage me all the time in Madison. I would like to dedicate my doctor’s degree to my aunt who has passed away during my study abroad.
I gratefully acknowledge the Vietnam Ministry of Education and Training for their financial support by a 4-year scholarship. I am also thankful the UW-Madison for additional financial support. ii TABLE OF CONTENTS ACKNOWLEDGEMENT. i TABLE OF CONTENTS .ii LIST OF FIGURES.vii LIST OF TABLES.
xiii CHAPTER ONE INTRODUCTION. SUMMARY OF THE LITERATURE REVIEW. 10 PVD-Soil (PVD-S) apparatus. 11 Smear Zone Model (SZM) device.
ORGANIZATION OF THE THESIS. 13 CHAPTER TWO EFFECT OF DEFORMATION OF PREFABRICATED VERTICAL DRAIN (PVD) ON DISCHARGE CAPACITY. FACTORS WITH POTENTIAL EFFECTS ON DISCHARGE CAPACITY. PVD structure and flexural stiffness.
Deformation Patterns of PVDs. REQUIRED DISCHARGE CAPACITY. 46 CHAPTER THREE THE CHARACTERISTICS OF THE PVD SMEAR ZONE. Pore Water Pressure Variation during PVD Installation.2 Variation of Total Head before and after PVD Installation.
Variation of Other Properties Measured. Effect of Soil Types on the Extent of the Smear Zone. EFFECT OF SMEAR ZONE ON CONSOLIDATION RATE. 86 CHAPTER FOUR CONCLUSIONS AND RECOMMENDATIONS.
SUMMARY AND CONCLUSIONS. Effect of PVD deformation on discharge capacity. The characteristics of the smear zone. 92 APPENDIX A A REVIEW OF THE USE OF PVDs.
PROPERTIES OF PVD AND INSTALLATION. CONSOLIDATION THEORY FOR PVDs. Consolidation theory for pure radial drainage. Consolidation theory for combined vertical and radial drainage.
Time-dependent loading. THE CHARACTERISTICS OF A FILTER SLEEVE. Soil retention ability. Discharge capacity tests without a soil confinement, “index test”.
The discharge capacity tests with a soil confinement, “Performance test” 127 A. Creep Deformation of PVDs. Required Discharge Capacity. THE CHARATERISTICS OF A SMEAR ZONE.
Tensile strength and modulus of the whole PVD. Tensile strength and modulus of the filter. 165 APPENDIX B DEVELOPMENT OF A PVD-SOIL MODE TEST (PVD-S) APPARATUS. THE PVD-S APPARATUS.
190 APPENDIX C DEVELOPMENT OF A SMEAR ZONE MODEL TEST (SZM) DEVICE. THE SZM DEVICE. 199 APPENDIX D SUMMARY OF SOIL PROPERTIES. CRANEY ISLAND DREDGINGS PROPERTIES.
211 vii LIST OF FIGURES Figure 2. The features of the PVD-S apparatus with dimensions in millimeter; a) Main dimensions of the PVD-S apparatus, b) Arrangement of piezometers in radial directions 21 Figure 2. Discharge capacity of the four PVDs tested as a function of hydraulic gradient and percent settlement: a) PVD A, Kaolinite, b) PVD B, Kaolinite, c) PVD C, Kaolinite, d) PVD D, Kaolinite, e) PVD B, Craney Island 29 Figure 2. Normalized discharge capacity of the all PVDs tested (A, B, C, and D) varying with hydraulic gradient (data at each hydraulic gradient are for all percent settlement) 31 Figure 2.
Discharge capacity of the four PVDs tested under a hydraulic gradient of 0.1 as a function of percent settlement 33 Figure 2. Degree of reduction of discharge capacity under a hydraulic gradient of 0.1 as a function of percent settlement 35 Figure 2. Deformation patterns of the four PVDs tested at the termination of the tests 38 Figure 2. Discharge capacity of PVD B in Kaolinite and Craney Island dredgings: (a) Discharge capacity as a function of percent settlement and (b) Degree of discharge capacity reduction as a function of percent settlement 40 Figure 2.
Increase in time for consolidation (Th,w/Th) due to well resistance for a 20m drainage length PVD with 1 m spacing in a triangular pattern (a) as a function of available discharge capacity; (b) as a function of settlement: Example calculation used k = 1x10-8 m/s with discharge capacity based on PVD B in Craney Island soil; others used the experimentally measured values for each soil and PVD 44 viii Figure 3. Smear Zone Model (SZM) Device with dimensions in millimeter; (a) Simulated soil zones surrounding the PVD after installation (b) Physical dimensions of SZM (simulated soil zone rotated 90o) 55 Figure 3. Variation of excess PWP during PVD installations (a) in Kaolinite (b) in Craney Island dredgings 65 Figure 3. Peak excess PWP during PVD installation (a) in Kaolinite, and (b) in Craney Island dredgings 67 Figure 3.
Total head distributions during verifying hydraulic uniformity prior to PVD installation by applying hydraulic head at the top, and collecting discharge water at the bottom of the SZM: (a) in Kaolinite and (b) in Craney Island dredgings 69 Figure 3. Total head distributions during the hydraulic conductivity tests after the PVD installations by applying hydraulic head at the top, and collecting discharge water at the two side reservoirs of the SZM: (a) in Kaolinite and (b) in Craney Island dredgings 71 Figure 3. Two soil zones distinguished by void ratio and hydraulic conductivity variance with distance from the PVD after the PVD installation for Craney Island dredgings 74 Figure 3. Variation of shear wave velocity and mass density with distance normal to the PVD after the SZM test on Craney Island dredgings 76 Figure 3.
Undrained shear strength and void ratio varying with the normal distance to the PVD after the SZM test on Craney Island dredgings 78 Figure 3. Effect of soil disturbance on the rate of consolidation for a PVD (spacing 1-m, triangular pattern, smear and transition zone characteristics as given in Table 4 for Craney Island dredgings 83 Figure 3. Time factor ratios corresponding to 90% degree of consolidation varying with PVD spacing in the triangular pattern (smear and transition zone hydraulic conductivities as given in Table 3.4 for Craney Island dredging 85 Figure A. The widely used PVDs employed for this study 102 Figure A.
Typical mandrels and detachable shoes (after Holtz et al. PVDs installed by a rig in the field 105 ix Figure A. A typical use of PVDs for a highway embankment on soft soil 107 Figure A. Arrangement patterns of PVDs on the plan view 108 Figure A.
The influence zone and equivalent diameter applying Barron solution (After Bo et al. Smear effect and well-resistance (After Holtz et al. The average degree of consolidation versus time factor ratio that takes both the vertical and horizontal direction into account (After Orleach 1983) 118 Figure A. Discharge capacity versus lateral stress (After Rixner et al.
Investigation of lateral stress effect on discharge capacity using the ENEL-CRIS in-soil test (After Bellotti and Pedroni 1986, Holtz et al. Long-term effects of lateral stress on discharge capacity from field tests (After Holtz et al. Possible deformations of PVDs under consolidation settlement (After Lawrence and Koerner 1988) 134 Figure A. ENEL-CRIS apparatus used to measure discharge capacity of initial sinusoidal bent PVDs (After Holtz et al.
Natural deformations of PVDs to accommodate soil consolidation settlement 136 Figure A. Investigation of discharge capacity of initially deformed PVDs using in-soil ENEL-CRIS device (After Holtz et al. Ali (1991) apparatus used for an investigation of effect of naturally deformed PVDs on discharge capacity 141 Figure A. The discharge capacity of different PVDs measured at various relative compressions under a hydraulic gradient of 0.5 using Ali’s apparatus (after Ali 1991) 142 Figure A.
The deformation of PVDs under various degrees of consolidation using a centrifugal model test device (After Morohoshi et al. Long-term effects of clogging on PVD discharge capacity (After Miura and Chai 2000) 147 Figure A. A smear zone model induced after PVD installation (a) (After Rixner et al. The PVD-S apparatus for investigations of the effect of deformed PVDs on discharge capacity with dimension in millimeter; Pi – piezometer i, PVD – prefabricated vertical drain 188 Figure B.
The final design of the PVD-S apparatus 189 Figure C. The detail SZM device with dimension in millimeter; (a) Soil zones surrounding a PVD after PVD installation, (b) the SZM simulating a rectangular box rotated in 90o covering the PVD in the center. The final design of the SZM device 198 Figure C. A rectangular mandrel used in this study 201 Figure D.
Consolidation behavior of Kaolinite obtained from an Oedometer test on a reconstituted specimen 205 Figure D. Coefficient of consolidation of Kaolinite calculated from Oedometer test data using the logarithm-of-time and square-root-of-time methods 206 Figure D. Hydraulic conductivity variance with void ratio of Kaolinite back calculated from the Oedometer test data 207 Figure D. Hydraulic conductivity variance with void ratio of Kaolinite measured on reconstituted specimens using rigid wall permeameters (ASTM D5856) 208 Figure D.
Liquid limit of Kaolinite using the wet-preparation method (ASTM D4318) 209 Figure D.
