水平地层地震动力反应分析
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摘要
根据Iai多重剪切机构塑性模型及边界面塑性模型的特点,建立了一个砂土多机构边界面塑性模型。该模型将土复杂的变形机理分解为体积机理和一系列简单的剪切机理。用边界面弹塑性模型模拟多重剪切机构塑性模型中虚拟单剪机构,避免了Iai多重剪切机构塑性模型在利用修正M asing准则模拟虚拟单剪应力应变关系时,确定比例参数的复杂性。根据大量试验资料,建立了液化面参数与归一累积剪切功的关系,能够用较少的参数很好地建立有效应力路径。由于多重机理的特性,模型能够模拟复杂荷载作用下主应力轴偏转的影响。用多机构边界面塑性模型对饱和砂土水平场地进行有效应力分析,对水平场地的地震反应特性进行了分析,由于多机构边界面塑性模型能同时考虑振动孔隙水压力的发展引起的有效应力降低导致饱和砂土抗剪强度和模量的降低。分析表明,结果是合理的。模型简单实用,将方便在工程实践中的应用。
According to the characteristics of Iai′s multiple mechanism plasticity model and boundary surface plasticity model,a multiple mechanism boundary surface plasticity model of saturated sand was established.The concept of multiple mechanism was used as a vehicle for decomposing the complex mechanism into a set of simple shear mechanisms defined in one dimensional space.Each virtual simple shear mechanism was simulated by the boundary surface plasticity model in the virtual stress and strain space,with which the complexity of getting the scale parameters was avoided when each virtual simple shear mechanism was simulated by the modified Masing′s rule in Iai′s multiple mechanism model.Based on a lot of test data,the relation between the liquefaction front parameter and the normalized shear work was presented.The effective stress path was well modeled by several parameters.The effect of rotation of principal stress axial directions and large shear displacement of sand in the earthquake induced liquefaction were taken into account at the same time in the model.The computed results were consistent with the laboratory results.Based on the multiple mechanism boundary surface plasticity model,an analysis of effective stress on the horizontal layer of the saturated sand and of the seismic response characteristics of the horizontal layer were given.The multiple mechanism boundary surface plasticity model simultaneously con-sidered the decrease of shear strength and the modulus of the saturated sand by the development of vibration pore water pressure.The analysis shows that the results are reasonable,and the model is simple and practical which makes the engineering application much easier.
According to the characteristics of Iai′s multiple mechanism plasticity model and boundary surface plasticity model,a multiple mechanism boundary surface plasticity model of saturated sand was established.The concept of multiple mechanism was used as a vehicle for decomposing the complex mechanism into a set of simple shear mechanisms defined in one dimensional space.Each virtual simple shear mechanism was simulated by the boundary surface plasticity model in the virtual stress and strain space,with which the complexity of getting the scale parameters was avoided when each virtual simple shear mechanism was simulated by the modified Masing′s rule in Iai′s multiple mechanism model.Based on a lot of test data,the relation between the liquefaction front parameter and the normalized shear work was presented.The effective stress path was well modeled by several parameters.The effect of rotation of principal stress axial directions and large shear displacement of sand in the earthquake induced liquefaction were taken into account at the same time in the model.The computed results were consistent with the laboratory results.Based on the multiple mechanism boundary surface plasticity model,an analysis of effective stress on the horizontal layer of the saturated sand and of the seismic response characteristics of the horizontal layer were given.The multiple mechanism boundary surface plasticity model simultaneously con-sidered the decrease of shear strength and the modulus of the saturated sand by the development of vibration pore water pressure.The analysis shows that the results are reasonable,and the model is simple and practical which makes the engineering application much easier.
引文
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[9]陈国兴,谢君斐,韩炜,等.土体地震反应分析的简化有效应力法[J].地震工程与工程振动,1995,15(2):52-61.CHEN Guo-xing,XIE Jun-fei,HAN Wei,et al.Asimplified effective stress method of soil mass earth-quake response analysis[J].Earthquake Engineeringand Engineering Vibration,1995,15(2):52-61.(inChinese).
[2]丰土根.饱和砂土不排水动力特性及多机构边界面塑性模型研究[D].南京:河海大学,2002.
[3]丰土根,刘汉龙,高玉峰,等.偏压固结砂土不排水循环性状分析[C].北京:清华大学出版社,2003.
[4]丰土根,刘汉龙,高玉峰,等.砂土多机构边界面塑性模型初探[J].岩土工程学报,2002,24(3):382-385.FENG Tu-gen,LIU Han-long,GAO Yu-feng,et al.Multiple mechanism boundary surface plasticity modelof sand[J].Chinese Journal of Geotehnical Engineer-ing.2002,24(3):382-385.(in Chinese).
[5]丰土根,刘汉龙,高玉峰.边界面及多重剪切机构模型研究现状[J].河海大学学报,1999,27(力学专辑):99-105.FENG Tu-gen,LIU Han-long,GAO Yu-feng.Stateof arts of boundary surface and multiple mechanismplasticity model[J].Journal of Hohai University,1999,27(s1):99-105.(in Chinese).
[6]丰土根,刘汉龙,Susumu Iai.砂土多机构边界面塑性模型的微观力学背景[C].第六届全国土动力学学术会议,北京:中国建筑工业出版社,2002.
[7]刘汉龙,丰土根,高玉峰,等.砂土多机构边界面塑性模型及其试验验证[J].岩土力学,2003,24(5):696-700.LIU Han-long,FENG Tu-gen,GAO Yu-feng,et al.Multiplemechanism boundary surface of saturatedsand and its test validation[J].Rock and Soil Mechan-ics,2003,24(5):696-700.(in Chinese).
[8]刘汉龙,丰土根.砂土多机构边界面塑性模型的改进[D].北京:中国建筑工业出版社,2002.
[9]陈国兴,谢君斐,韩炜,等.土体地震反应分析的简化有效应力法[J].地震工程与工程振动,1995,15(2):52-61.CHEN Guo-xing,XIE Jun-fei,HAN Wei,et al.Asimplified effective stress method of soil mass earth-quake response analysis[J].Earthquake Engineeringand Engineering Vibration,1995,15(2):52-61.(inChinese).
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