地震荷载不规则性对砂土震陷的影响
|
摘要
利用有限元数值方法模拟不同类型砂土在多向地震荷载输入条件下的动单剪试验,采用弹塑性边界面模型,通过室内动单剪试验实测结果确定模型参数,计算分析地震动特性对砂土震陷的影响。研究结果表明:地震波加载次序、不对称性、加载方向、地震波类型、加载维数对砂土变形影响显著。当大的应力脉冲出现时,砂土竖向应变明显增大,其增量的大小受到大波出现的时刻和次序影响明显;在其他条件相同时,地震波不对称性越明显,砂土竖向应变越大;反向加载对砂土具有向下压应力作用,提高竖向应变值,正向加载效应则与此相反;现有的一些规范方法取20周作为转换后的等幅应力波的标准作用次数进行震陷定量计算,其对于振动型和冲击型地震波输入等效性结果差别较大;Tokimatsu和Seed(1987)震陷分析方法按2倍单向水平地震动引起的砂土震陷简化确定多向地震动引起的砂土震陷,其结果尚待商榷。
Dynamic simple shear tests on different types of sands under multidirectional earthquake loading were simulated with finite element method.Reduced order bounding surface model was employed to study the effect of characteristics of earthquake loading on the seismic compression of sands.The parameters of model were determined based on results obtained from laboratory dynamic simple shear tests.The study results show that the characteristics of earthquake loading such as loading sequence,asymmetry,loading direction,loading type and input loading dimension have great influence on seismic compression of sand.The vertical strain of sand increases dramatically when sand specimen is subjected to high stress pulse;also its increment is greatly influenced by time and sequence of stress pulse;the vertical strain of sands increases as the asymmetry of earthquake loading grows under identical conditions;negative loading results in increase of vertical strain of sand due to its compaction effect,which is opposite to positive loading effect;20 cycles were used simply as the number of equivalent cycle in some current codes for computation of seismic compression,whose equivalences for vibration-type and impact-type of seismic loading is greatly different;two times of seismic compression of sand induced by one component loading was taken as the sum of seismic compression of sand induced by actual multidirectional earthquake loading in Tokimatsu and Seed(1987) procedure,which is in doubt.
Dynamic simple shear tests on different types of sands under multidirectional earthquake loading were simulated with finite element method.Reduced order bounding surface model was employed to study the effect of characteristics of earthquake loading on the seismic compression of sands.The parameters of model were determined based on results obtained from laboratory dynamic simple shear tests.The study results show that the characteristics of earthquake loading such as loading sequence,asymmetry,loading direction,loading type and input loading dimension have great influence on seismic compression of sand.The vertical strain of sand increases dramatically when sand specimen is subjected to high stress pulse;also its increment is greatly influenced by time and sequence of stress pulse;the vertical strain of sands increases as the asymmetry of earthquake loading grows under identical conditions;negative loading results in increase of vertical strain of sand due to its compaction effect,which is opposite to positive loading effect;20 cycles were used simply as the number of equivalent cycle in some current codes for computation of seismic compression,whose equivalences for vibration-type and impact-type of seismic loading is greatly different;two times of seismic compression of sand induced by one component loading was taken as the sum of seismic compression of sand induced by actual multidirectional earthquake loading in Tokimatsu and Seed(1987) procedure,which is in doubt.
引文
[1]袁晓铭,孙锐,孟上九.土体地震大变形分析中Seed有效循环次数方法的局限性[J].岩土工程学报,2004,26(2):207-211.YUAN Xiao-ming,SUN Rui,MENG Shang-jiu.Limitation of the Seed's method of significant cyclic number in analyzing large deformation of soils during earthquake[J].Chinese Journal of Geotechnical Engineering,2004,26(2):207-211.
[2]NAGASE H,ISHIHARA K.Liquefaction-induced compaction and settlement of sand during earthquakes[J].Soils and Foundations,1988,28(1):65-76
[3]WHANG D,RIEMER M F,BRAY J D,et al.Characterization of seismic compression of some com-pacted fills[C]//Proceedings of Sessions of Geo-Denver 2000:Advances in Unsaturated Geotechnics.Denver:ASCE,2000:180-194.
[4]孟凡超.液化地基上建筑物不均匀震陷机理初步研究[D].哈尔滨:中国地震局工程力学研究所,2006.
[5]TOKIMATSU K,SEED H B.Evaluation of settlements in sands due to earthquake shaking[J].Journal of Geotechnical Engineering,1987,113(8):861-878.
[6]DUKU P M,STEWART J P,WHANG D H,et al.Volumetric strains of clean sands subject to cyclic loads[J].Journal of Geotechnical and Geoenviron-mental Engineering,2008,134(8):1073-1085.
[7]PRADEL D.Procedure to evaluate earthquake induced settlements in dry sandy soils[J].Journal of Geo-technical and Geoenvironmental Engineering,1998,124(4):364-368.
[8]STEWART J P,WHANG D H,MOYNEUR M,et al.Seismic compression of as-compacted fill soils with fines content and fines plasticity[R].Los Angeles:Department of Civil and Environmental Engineering,University of California,2004.
[9]吴世明.土动力学[M].北京:中国建筑工业出版社,2000.
[10]PYKE R,SEED H B,CHAN C K.Settlement of sands under multidirectional shaking[J].Journal of Geo-technical Engineering,ASCE,1975,101(4):378-398.
[11]YOUD T L.Compaction of sands by repeated shear straining[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1972,98(7):709-725.
[12]SHAHNAZARI H,TOWHATA I.Torsion shear tests on cyclic stress-dilatancy relationship of sand[J].Soils and Foundations,2002,42(1):105-119.
[13]WHANG D H,STEWART J P,BRAY J D.Effect of compaction conditions on the seismic compression of compacted fill soils[J].Geotechnical Testing Journal,2004,27(4):371-379.
[14]STAMATOPOULOS C A,BALLA L N,STAMATOP-OULOS A C.Earthquake-induced settlement as a result of densification,measured in laboratory tests[C]//13th World Conference on Earthquake Engineering.Vancouver BC,Canada:International Association for Earthquake Engineering,2004.
[15]DUKU P M,STEWART J P,WHANG D H.Effect of post-compaction ageing on seismic compression of fine-grained soils[C]//Proceedings of Sessions of Geo-Shanghai:Ground Modification and Seismic Mitigation.Shanghai:ASCE,2006:411-416.
[16]孟凡超,袁晓铭,孙锐.加速度峰值不对称性特征及其影响[J].自然灾害学报,2008,17(1):191-196.MENG Fan-chao,YUAN Xiao-ming,SUN Yue.Study of characteristics and effect of asymmetry of peak ground acceleration[J].Journal of Natural Disasters,2008,17(1):191-196.
[17]蔡宏英,周健,李相菘.深厚覆盖软土地层多向地震动力反应分析[J].同济大学学报,2000,28(2):177-182.CAI Hong-ying,ZHOU Jian,LI Xiang-song.Plasto-elastic dynamic response of horizontally layered sites under multi-directional earthquake shaking[J].Journal of Tongji University(Natural Science),2000,28(2):177-182.
[18]WANG Z L.Bounding surface hypoplasticity model for granular soils and its application[D].California:University of California,1990.
[19]LI X S,WANG Z L,SHEN C K,et al.A nonlinear procedure for response analysis of horizontally layered sites subjected to multi-directional earthquake loading[R].California:Department of Civil Engineering,University of California,1992.
[20]谢定义,巫志辉.不规则动荷脉冲波对砂土液化特性的影响[J].岩土工程学报,1987,9(4):1-12.XIE Ding-yi,WU Zhi-hui.Effect of irregular dynamic impulse history on liquefaction characteristics of saturated sand[J].Chinese Journal of Geotechnical Engineering,1987,9(4):1-12.
[21]ISHIHARA K,YASUDA S.Sand liquefaction under random earthquake loading condition[C]//Proceedings of the 5th World Conference on Earthquake Engineering.Rome:ASCE,1973:329-338.
[2]NAGASE H,ISHIHARA K.Liquefaction-induced compaction and settlement of sand during earthquakes[J].Soils and Foundations,1988,28(1):65-76
[3]WHANG D,RIEMER M F,BRAY J D,et al.Characterization of seismic compression of some com-pacted fills[C]//Proceedings of Sessions of Geo-Denver 2000:Advances in Unsaturated Geotechnics.Denver:ASCE,2000:180-194.
[4]孟凡超.液化地基上建筑物不均匀震陷机理初步研究[D].哈尔滨:中国地震局工程力学研究所,2006.
[5]TOKIMATSU K,SEED H B.Evaluation of settlements in sands due to earthquake shaking[J].Journal of Geotechnical Engineering,1987,113(8):861-878.
[6]DUKU P M,STEWART J P,WHANG D H,et al.Volumetric strains of clean sands subject to cyclic loads[J].Journal of Geotechnical and Geoenviron-mental Engineering,2008,134(8):1073-1085.
[7]PRADEL D.Procedure to evaluate earthquake induced settlements in dry sandy soils[J].Journal of Geo-technical and Geoenvironmental Engineering,1998,124(4):364-368.
[8]STEWART J P,WHANG D H,MOYNEUR M,et al.Seismic compression of as-compacted fill soils with fines content and fines plasticity[R].Los Angeles:Department of Civil and Environmental Engineering,University of California,2004.
[9]吴世明.土动力学[M].北京:中国建筑工业出版社,2000.
[10]PYKE R,SEED H B,CHAN C K.Settlement of sands under multidirectional shaking[J].Journal of Geo-technical Engineering,ASCE,1975,101(4):378-398.
[11]YOUD T L.Compaction of sands by repeated shear straining[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1972,98(7):709-725.
[12]SHAHNAZARI H,TOWHATA I.Torsion shear tests on cyclic stress-dilatancy relationship of sand[J].Soils and Foundations,2002,42(1):105-119.
[13]WHANG D H,STEWART J P,BRAY J D.Effect of compaction conditions on the seismic compression of compacted fill soils[J].Geotechnical Testing Journal,2004,27(4):371-379.
[14]STAMATOPOULOS C A,BALLA L N,STAMATOP-OULOS A C.Earthquake-induced settlement as a result of densification,measured in laboratory tests[C]//13th World Conference on Earthquake Engineering.Vancouver BC,Canada:International Association for Earthquake Engineering,2004.
[15]DUKU P M,STEWART J P,WHANG D H.Effect of post-compaction ageing on seismic compression of fine-grained soils[C]//Proceedings of Sessions of Geo-Shanghai:Ground Modification and Seismic Mitigation.Shanghai:ASCE,2006:411-416.
[16]孟凡超,袁晓铭,孙锐.加速度峰值不对称性特征及其影响[J].自然灾害学报,2008,17(1):191-196.MENG Fan-chao,YUAN Xiao-ming,SUN Yue.Study of characteristics and effect of asymmetry of peak ground acceleration[J].Journal of Natural Disasters,2008,17(1):191-196.
[17]蔡宏英,周健,李相菘.深厚覆盖软土地层多向地震动力反应分析[J].同济大学学报,2000,28(2):177-182.CAI Hong-ying,ZHOU Jian,LI Xiang-song.Plasto-elastic dynamic response of horizontally layered sites under multi-directional earthquake shaking[J].Journal of Tongji University(Natural Science),2000,28(2):177-182.
[18]WANG Z L.Bounding surface hypoplasticity model for granular soils and its application[D].California:University of California,1990.
[19]LI X S,WANG Z L,SHEN C K,et al.A nonlinear procedure for response analysis of horizontally layered sites subjected to multi-directional earthquake loading[R].California:Department of Civil Engineering,University of California,1992.
[20]谢定义,巫志辉.不规则动荷脉冲波对砂土液化特性的影响[J].岩土工程学报,1987,9(4):1-12.XIE Ding-yi,WU Zhi-hui.Effect of irregular dynamic impulse history on liquefaction characteristics of saturated sand[J].Chinese Journal of Geotechnical Engineering,1987,9(4):1-12.
[21]ISHIHARA K,YASUDA S.Sand liquefaction under random earthquake loading condition[C]//Proceedings of the 5th World Conference on Earthquake Engineering.Rome:ASCE,1973:329-338.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心