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研究生： 汪俊彥
Jyun-Yen Wang
論文名稱： Experimental Study on Seepage Failure of Uniform and Gap-Graded Soils
Experimental Study on Seepage Failure of Uniform and Gap-Graded Soils
指導教授： 楊國鑫
Kuo-Hsin Yang
口試委員: 吳朝賢
Chau-Shian Wu
吳富春
Fu-Chun Wu
歐章煜
Chang-Yu Ou
學位類別： 碩士
Master
系所名稱： 工程學院 - 營建工程系
Department of Civil and Construction Engineering
論文出版年： 2012
畢業學年度： 100
語文別： 英文
論文頁數： 149
中文關鍵詞： Soil piping 、Internal stability 、Internal erosion 、Uniform sand 、Gap-graded sand 、Critical hydraulic gradient 、Upward seepage test
外文關鍵詞： Soil piping, Internal stability, Internal erosion, Uniform sand, Gap-graded sand, Critical hydraulic gradient, Upward seepage test
相關次數： 點閱：295  下載：4 
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    • Soil piping is a hydraulic and geotechnical phenomenon that soil hydraulic fails due to seepage. Soil piping can happen in geotechnical engineering and ecosystem. An upward seepage testing system is developed to study the seepage failure of soil. The testing system consists of a transparent acrylic permeameter, a constant head device and a data acquisition system. Using this test apparatus, a series of experiments on uniform sand and gap-graded sand are carried out to observe the process of seepage failure of specimen and to determine the critical hydraulic gradient. This study found the seepage failure mode is depended on the internal stability of soil which mainly depends on the grain size distribution and can be assessed using stable criteria. Test result shows seepage failure of uniform sand (internally sable soil) typically experiences an expansion of specimen thickness and the liquefaction of specimen, which is associated with the condition of effective stress equals zero. Seepage failure of gap-graded sand (internally unstable soil) is related to the internal erosion of fines which shows the finer particles in specimen will be vigorously eroded out with upward seepage flow, but the coarser particles remain comparatively stable. Further, the critical hydraulic gradients icr of soil obtained from test are compared with the predicted icr using theoretical equation proposed by Terzaghi. It is found the values of icr of uniform sand range from 0.89 to 1.21 which are close to the predicted icr. The values of icr of gap-graded sand range from 0.27 to 0.43 are far lower than the predicted icr. A database of icr of soil is compiled from this study and relevant literatures, and is used to compare different icr prediction methods and identify a best prediction method. Comparison result shows there is no a best methods can accurate predict the icr for all types of soils, but Terzaghi’s equation can predict the icr well of soil which satisfies the stable criterion proposed by Kenny and Lau (1985). Finally, this study is expected to provide the contribution in geotechnical engineering for a better understanding of seepage failure of soil and their critical hydraulic gradient.

    Soil piping is a hydraulic and geotechnical phenomenon that soil hydraulic fails due to seepage. Soil piping can happen in geotechnical engineering and ecosystem. An upward seepage testing system is developed to study the seepage failure of soil. The testing system consists of a transparent acrylic permeameter, a constant head device and a data acquisition system. Using this test apparatus, a series of experiments on uniform sand and gap-graded sand are carried out to observe the process of seepage failure of specimen and to determine the critical hydraulic gradient. This study found the seepage failure mode is depended on the internal stability of soil which mainly depends on the grain size distribution and can be assessed using stable criteria. Test result shows seepage failure of uniform sand (internally sable soil) typically experiences an expansion of specimen thickness and the liquefaction of specimen, which is associated with the condition of effective stress equals zero. Seepage failure of gap-graded sand (internally unstable soil) is related to the internal erosion of fines which shows the finer particles in specimen will be vigorously eroded out with upward seepage flow, but the coarser particles remain comparatively stable. Further, the critical hydraulic gradients icr of soil obtained from test are compared with the predicted icr using theoretical equation proposed by Terzaghi. It is found the values of icr of uniform sand range from 0.89 to 1.21 which are close to the predicted icr. The values of icr of gap-graded sand range from 0.27 to 0.43 are far lower than the predicted icr. A database of icr of soil is compiled from this study and relevant literatures, and is used to compare different icr prediction methods and identify a best prediction method. Comparison result shows there is no a best methods can accurate predict the icr for all types of soils, but Terzaghi’s equation can predict the icr well of soil which satisfies the stable criterion proposed by Kenny and Lau (1985). Finally, this study is expected to provide the contribution in geotechnical engineering for a better understanding of seepage failure of soil and their critical hydraulic gradient.

    CHAPTER 1 INTRODUCTION 1.1 BACKGROUND 1.2 OBJECTIVES 1.3 ORGANIZATION of THESIS CHAPTER 2 LITERATURE REVIEW 2.1 INTRODUCTION 2.1.1 Seepage flows in soils 2.1.2 Soil piping problem in civil engineering 2.1.3 Ecological aspect of soil piping 2.2 MECHANISMS and HYDRAULIC CONDITION of SOIL PIPING 2.3 PREVIOUS RESEARCHES on INTERNALLY UNSTABLE SOIL 2.3.1 General concept 2.3.2 Origination of the studies on internally unstable soils 2.3.4 Assessment of internal stability of soil by empirical criteria 2.3.4.1 Istomina (1957) 2.3.4.2 Kezdi (1979) 2.3.4.3 Kenney and Lau (1985, 1986) 2.4 PREVIOUS RESEARCHES on SEEPAGE FAILURE of SOIL 2.4.1 Generally experimental approaches on soil piping 2.4.2 Experimental studies on soil piping 2.4.2.1 Tanaka and Toyokuni (1991) 2.4.2.2 Skempton and Brogan (1994) 2.4.2.3 Morz et al. (2007) 2.4.2.4 Ahlinhan and Achmus (2010) 2.4.4 Prediction methods of critical hydraulic gradient of soil piping 2.4.4.1 Terzaghi (1939) 2.4.4.2 Wu (1980) 2.4.4.3 Khilar et al. (1985) 2.4.4.4 Liu (1992) 2.4.4.3 Zhou et al. (2010) 2.5 SUMMARY CHAPTER 3 EXPERIMENTAL TEST PROGRAM 3.1 SOIL PIPING TEST SYSTEM 3.1.1 Permeameter 3.1.2 Water supply system 3.1.3 Instrumentation 3.1.4 Data acquisition system 3.1.4.1 Transducer 3.1.4.2 Amplifier 3.1.4.3 DAQ device 3.1.3.4 Software 3.2 TEST SOILS 3.3 TEST PROCEDURE 3.3.1 Specimen preparation 3.3.2 Application of hydraulic gradient 3.4 TEST PROGRAM 3.4.1 Preliminary series test 3.4.2 Main series test CHAPTER 4 TEST RESULTS AND DISCUSSIONS 4.1 DEFINITIONS of HYDRAULIC PROPERTIES of SOIL and FAILURE CONDITION 4.2 PRELIMINARY SERIES TESTS 4.2.1 Effect of specimen dimension on test results 4.2.2 Effect of porous screen type on test results 4.2.3 Summary of preliminary series tests 4.3 MAIN SERIES TESTS 4.3.1 Uniform Fu-Long beach sand (B3) 4.3.1.1 Test result of B3-1 4.3.1.2 Test result of B3-2 4.3.1.3 Test result of B3-3 4.3.1.4 Test result of B3-4 4.3.1.5 Test result of B3-5 4.3.2 Uniform quartz sand (C3) 4.3.2.1 Test result of C3-1 4.3.2.2 Test result of C3-2 4.3.2.3 Test result of C3-3 4.3.2.4 Test result of C3-4 4.3.2.5 Test result of C3-5 4.3.3 Gap-graded sand (G3) 4.3.3.1 Test result of G3-1 4.3.3.2 Test result of G3-2 4.3.3.3 Test result of G3-3 4.3.3.4 Test result of G3-4 4.3.3.5 Test result of G3-5 4.4 COMPARISON of EFFECTIVE STRESS in SPECIMEN at icr 4.5 DISCUSSIONS on MAIN SERIES TEST RESULTS CHAPTER 5 ANALYSES, RESULTS AND DISCUSSIONS 5.1 COMPILATION of EXPERIMETNAL DATABASE 5.1.1 Data from this study 5.1.2 Data from Skempton and Brogan (1994) 5.1.3 Data from Morz et al. (2007) 5.1.4 Data from Mao et al. (2009) 5.1.5 Data from Ahlinhan and Achmus (2010) 5.1.6 Data from Ke and Takahashi (2011) 5.2 EXAMINATION of icr PREDICTION METHODS 5.2.1 Definition of model bias 5.2.2 icr prediction methods and prediction results 5.2.3 Soil internal stability criteria and assessment results 5.3 COMPARISON of icr PREDICTION METHODS 5.3.1 Overall comparison 5.3.2 Comparison based on the soil internal stability 5.3.2.1 Comparison of icr prediction methods under internal stable soil cases 5.3.2.2 Comparison of icr prediction methods under internal unstable soil cases 5.4 DISCUSSIONS on COMPARISON RESULTS 5.5 SUGGESTIONS for ENGINEERING APPLICATIONS CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS 6.1 CONCLUSIONS of THIS STUDY 6.2 RECOMMENDATIONS of THIS STUDY REFERENCE

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