动扭剪试验中砂土液化后流动特性分析
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摘要
土体在初始液化后仍然可能承受动荷载作用发生大变形。引入流体力学中的剪应变率和表观黏度的概念,对振动扭剪试验中饱和砂土液化后的流动特性进行了分析。分析中将砂土的状态分为0有效应力状态和非0有效应力状态。结果表明,砂土在0有效应力状态下表现出与静扭剪试验类似的"剪切稀化"非牛顿流体的特征,表观黏度随着剪应变率的增大而减小。加载周数对"剪切稀化"状态下的剪应变率幅值有影响,随着加载周数的增加,剪应变率幅值逐渐增大,而对流动曲线的形状没有影响。在非0有效应力状态下,砂土的表观黏度随应变的增大而增大,随孔压比的减小而增大,且所有的试验得到的表观黏度与孔压比具有一致关系。
Large deformation may occur in the post initial liquefied sand undergone the dynamic loading.The definitions of shear strain rate and apparent viscosity in fluid mechanics are introduced to analyze the dynamic hollow torsional tests of post initial liquefied sand.There are two states in the post liquefied sand: zero effective stress state and non-zero effective stress state.The conclusions show that the sand characterized by shear-thinning non-Newtonian fluid in zero effective stress state which is similar to the static torsional tests.The loading cycle number does not have influence on the shape of flow curves under shear–thinning state except for the amplitude of shear strain rate,which increases with the increase of cycle number.Under non–zero effective stress state,the apparent viscosity increases with the increase of strain and the decrease of pore pressure.The apparent viscosity,which obtained from all tests,has a unitary formulation with the pore pressure ratio.
Large deformation may occur in the post initial liquefied sand undergone the dynamic loading.The definitions of shear strain rate and apparent viscosity in fluid mechanics are introduced to analyze the dynamic hollow torsional tests of post initial liquefied sand.There are two states in the post liquefied sand: zero effective stress state and non-zero effective stress state.The conclusions show that the sand characterized by shear-thinning non-Newtonian fluid in zero effective stress state which is similar to the static torsional tests.The loading cycle number does not have influence on the shape of flow curves under shear–thinning state except for the amplitude of shear strain rate,which increases with the increase of cycle number.Under non–zero effective stress state,the apparent viscosity increases with the increase of strain and the decrease of pore pressure.The apparent viscosity,which obtained from all tests,has a unitary formulation with the pore pressure ratio.
引文
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[14]刘汉龙,周云东,余湘娟,等.多功能静动三轴仪研制及在液化后大变形中的应用[J].大坝观测与土工测试,2001,25(5):48-51.LIU Han-long,ZHOU Yun-dong,YU Xiang-juan,et al.Design of static-dynamic dual purpose triaxial compression test apparatus and its application in the study of earthquake-induced large deformation[J].Dam Observation and Geotechnical Tests,2001,25(5):48-51.
[15]沈崇堂,刘鹤年.非牛顿流体力学及其应用[M].北京:高等教育出版社,1989:20-45.
[2]刘汉龙,周云东,高玉峰.砂土地震液化后大变形特性试验研究[J].岩土工程学报,2002,24(2):142-146.LIU Han-long,ZHOU Yun-dong,GAO Yu-feng.Study on the behavior of large ground displacement of sand due to seismic liquefaction[J].Chinese Journal of Geotechnical Engineering,2002,24(2):142-146.
[3]周云东.地震液化引起的地面大变形试验研究[D].南京:河海大学,2003.
[4]SHAMOTO Y,ZHANG J M,GOTO S.Mechanism of large post-liquefaction deformation in saturated sand[J].Soils and Foundations,1997,37(2):71-80.
[5]ZHANG J M,SHAMOTO Y,TOKIMATSU K.Moving critical and phase-transformation stress state lines of saturated sand during undrained cyclic shear[J].Soils and Foundations,1997,37(2):51-59.
[6]WANG Z L,DAFAILIAS Y,SHEN C K.Bounding surface hypoplasticity model for sand[J].Journal of Engineering Mechanics,ASCE,1990,116(5):983-1001.
[7]IAI S,MATSUNAGA Y,KAMEOKA T.Strain space plasticity model for cyclic mobility[J].Soils and Foundations,1992,32(2):1-15.
[8]ZHANG J M,WANG G.A constitutive model for evaluating small to large cyclic strains of saturated sand during liquefaction process[J].Chinese Journal of Geotechnical Engineering,2004,26(4):546-552.
[9]TOWHATA I,SASAKI Y,TOKIDA K I,et al.Prediction of permanent displacement of liquefied ground by means of minimum energy principle[J].Soils and Foundations,1992,32(3):97-116.
[10]UZUOKA R,YASHIMA A,KAWAKAMI T,et al.Fluid dynamics based prediction of liquefaction induced lateral spreading[J].Computers and Geotechnics,1998,22(3/4):243-282.
[11]TOWHATA I,VARGAS-MONGE W,ORENSE R P,et al.Shaking table tests on subgrade reaction of pipe embedded in sandy liquefied subsoil[J].Soil Dynamics and Earthquake Engineering,1999,18:347-361.
[12]陈育民,周云东.基于流体力学方法的砂土液化后研究进展[J].河海大学学报(自然科学版),2007,35(4):418-421.CHEN Yu-min,ZHOU Yun-dong.Advance in sand post-liquefaction research based on fluid mechanics method[J].Journal of Hohai University(Natural Science Edition),2007,35(4):418-421.
[13]陈育民,刘汉龙,周云东.液化及液化后砂土的流动特性分析[J].岩土工程学报,2006,28(9):1139-1143.CHEN Yu-min,LIU Han-long,ZHOU Yun-dong.Analysis on the flow characteristics of liquefied and post-liquefied sand[J].Chinese Journal of Geotechnical Engineering,2006,28(9):1139-1143.
[14]刘汉龙,周云东,余湘娟,等.多功能静动三轴仪研制及在液化后大变形中的应用[J].大坝观测与土工测试,2001,25(5):48-51.LIU Han-long,ZHOU Yun-dong,YU Xiang-juan,et al.Design of static-dynamic dual purpose triaxial compression test apparatus and its application in the study of earthquake-induced large deformation[J].Dam Observation and Geotechnical Tests,2001,25(5):48-51.
[15]沈崇堂,刘鹤年.非牛顿流体力学及其应用[M].北京:高等教育出版社,1989:20-45.
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