有地下结构的饱和砂土液化宏细观离心机试验
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摘要
利用自行设计的离心机细观图像观测系统,在离心机上对有地下结构的饱和砂土层进行了地震液化宏细观模型试验。离心机细观图像观测系统主要由高速摄像机、地铁车站模型和工控机组成。摄像机安装在地铁车站模型内部,通过深埋和浅埋车站模型可以实时动态记录地震发生过程中砂土地基不同深度砂颗粒运动细观图像,同时测量了加速度和超孔隙水压力等宏观地震响应特性。利用图像处理技术对拍摄的细观照片进行分析,从颗粒运动特性、颗粒长轴定向、接触法向、接触数和孔隙率等细观组构参量的动态变化揭示不同深度的饱和砂土地基液化的细观机制。试验表明:深层砂土在地震作用下的运动表现为类似管涌特征,颗粒长轴经过地震后偏向竖直方向,而浅层砂土的运动表现为砂沸,颗粒长轴排列地震后较均匀。饱和砂土地震响应宏观特征与细观组构变化具有良好的一致性。试验结果有助于从细观层面揭示砂土液化的机理。
A new image observation system is designed for recording the motion of sand particles during the shaking event in centrifuge tests.It involves high-speed video camera,metro station model and industrial computer.The camera is installed inside the metro station model.With the metro station model shallowly and deeply buried respectively,the motion of sand particles at various elevations is real-time recorded during earthquake occurrence.The digital images at certain stages of the tests are processed by self-developed software named GeoDIP.The micro-mechanism of liquefaction of sandy foundation at different depths are analyzed by the micro-fabric evolutions of sand particles,which includes particle orientation,contact normal and number of particles and porosity ratio.Furthermore,labeled particles are traced to study the micro-mechanism of soil deformation.The test results show that the particle motion at deep depth is similar to piping and there is preferred orientation of vertical direction of the long axis of particles after post-liquefaction drainage.Nevertheless,the motion of shallow particles is similar to sand boil and there is no preferred orientation of particles.The macro response of saturated sandy foundation such as acceleration and excess pore pressure accords with the micro-fabric evolutions of sand particles in centrifuge tests.The results have indicated that the image observation system is a valuable tool that can properly characterize the liquefaction behaviors from microscope and provide an insight into a phenomenon previously impossible.
A new image observation system is designed for recording the motion of sand particles during the shaking event in centrifuge tests.It involves high-speed video camera,metro station model and industrial computer.The camera is installed inside the metro station model.With the metro station model shallowly and deeply buried respectively,the motion of sand particles at various elevations is real-time recorded during earthquake occurrence.The digital images at certain stages of the tests are processed by self-developed software named GeoDIP.The micro-mechanism of liquefaction of sandy foundation at different depths are analyzed by the micro-fabric evolutions of sand particles,which includes particle orientation,contact normal and number of particles and porosity ratio.Furthermore,labeled particles are traced to study the micro-mechanism of soil deformation.The test results show that the particle motion at deep depth is similar to piping and there is preferred orientation of vertical direction of the long axis of particles after post-liquefaction drainage.Nevertheless,the motion of shallow particles is similar to sand boil and there is no preferred orientation of particles.The macro response of saturated sandy foundation such as acceleration and excess pore pressure accords with the micro-fabric evolutions of sand particles in centrifuge tests.The results have indicated that the image observation system is a valuable tool that can properly characterize the liquefaction behaviors from microscope and provide an insight into a phenomenon previously impossible.
引文
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[6]ARULANANDAN K,SCOTT R F.Project VELACS-controltest results[J].Journal of the Geotechnical Engineering,ASCE,1993,119(8):1276-1292.
[7]TABOADA V M,DOBRY R.Experimental results of modelNo.1 at RPI[C]//Arulanandan K,Scott R F,ed.Proceedingsof the International Conference on Vertification of NumericalProcedures for the Analysis of Soil Liquefaction Problems.Rotterdam:A A Balkema,1993:3-17.
[8]GONZáLEZ LENART,ABDOUN TAREK,et al.Physicalmodeling and visualization of soil liquefaction under highconfining stress[J].Earthquake Engineering and EngineeringVibration,2005,4(1):47-57.
[9]ZEGHAL M,KALLOU P V,OSKAY C.Identification andimaging of soil and soil-pile deformation in the presence ofliquefaction[J].Earthquake Engineering and EngineeringVibration,2006,5(2):171-182.
[10]ODA M,KAWAMOTO K,SUZUKI K,et al.Micorstructuralinterpretation on reliquefaction of saturated granular soilsunder cyclic loading[J].Journal of Geotechnical andGeoenvironmental Engineering,2001,127(5):416-423.
[11]周健,余荣传,贾敏才.基于数字图像技术的砂土模型试验细观结构参数测量[J].岩土工程学报,2006,28(12):2047-2052.(ZHOU Jian,YU Rong-chuan,JIA Min-cai.Measurement of microstructure parameters for granular soilmodel using digital image technology[J].Chinese Journal ofGeotechnical Engineering,2006,28(12):2047-2052.(inChinese))
[12]SU Dong,Centrifuge investigation on responses of sanddeposit and sand-pile system under multi-directionalearthquake loading[D].Hong Kong:Hong Kong Universityof Science and Technology,2005.
[2]HUSHMAND B,SCOTT R F,CROUSE C B.Centrifugeliquefaction tests in a laminar box[J].Géotechnique,1988,38(2):253-262.
[3]LING H I,MOHRI Y,KAWABATA T,et al.Centrifugalmodeling of seismic behavior of large-diameter pipe inliquefiable soil[J].Journal of Geotechnical andGeoenvironmental Engineering,2003,129(2):1092-1101.
[4]MOURAD ZEGHAL,AHMED-W EIGAMAL,XIANG WUZENG.Mechanism of liquefaction response in sand-siltdynamic centrifuge tests[J].Soil Dynamics and EarthquakeEngineering,1999,18(1):71-85.
[5]刘光磊,宋二祥,刘华北.可液化地层中地铁隧道地震响应数值模拟及其试验验证[J].岩土工程学报,2007,29(12):1815-1822.(LIU Guang-lei,SONG Er-xiang,LIU Hua-bei.Numerical modeling of subway tunnels in liquefiable soilunder earthquakes and verification by centrifuge tests[J].Chinese Journal of Geotechnical Engineering,2007,29(12):1815-1822.(in Chinese))
[6]ARULANANDAN K,SCOTT R F.Project VELACS-controltest results[J].Journal of the Geotechnical Engineering,ASCE,1993,119(8):1276-1292.
[7]TABOADA V M,DOBRY R.Experimental results of modelNo.1 at RPI[C]//Arulanandan K,Scott R F,ed.Proceedingsof the International Conference on Vertification of NumericalProcedures for the Analysis of Soil Liquefaction Problems.Rotterdam:A A Balkema,1993:3-17.
[8]GONZáLEZ LENART,ABDOUN TAREK,et al.Physicalmodeling and visualization of soil liquefaction under highconfining stress[J].Earthquake Engineering and EngineeringVibration,2005,4(1):47-57.
[9]ZEGHAL M,KALLOU P V,OSKAY C.Identification andimaging of soil and soil-pile deformation in the presence ofliquefaction[J].Earthquake Engineering and EngineeringVibration,2006,5(2):171-182.
[10]ODA M,KAWAMOTO K,SUZUKI K,et al.Micorstructuralinterpretation on reliquefaction of saturated granular soilsunder cyclic loading[J].Journal of Geotechnical andGeoenvironmental Engineering,2001,127(5):416-423.
[11]周健,余荣传,贾敏才.基于数字图像技术的砂土模型试验细观结构参数测量[J].岩土工程学报,2006,28(12):2047-2052.(ZHOU Jian,YU Rong-chuan,JIA Min-cai.Measurement of microstructure parameters for granular soilmodel using digital image technology[J].Chinese Journal ofGeotechnical Engineering,2006,28(12):2047-2052.(inChinese))
[12]SU Dong,Centrifuge investigation on responses of sanddeposit and sand-pile system under multi-directionalearthquake loading[D].Hong Kong:Hong Kong Universityof Science and Technology,2005.
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