砂土液化流动变形的简化方法
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摘要
已有的液化砂土流动特性试验结果表明,砂土在液化流动状态下是剪切稀化非牛顿流体,可以用幂函数表示其剪应力-剪应变率的关系,从而建立了砂土液化流动的本构方程。基于FLAC3D程序的二次开发平台,将液化流动本构方程开发到FLAC3D中,建立了液化流动变形的简化分析方法。通过倾斜场地的液化流动变形分析,发现倾斜场地的液化变形曲线可以用正弦函数曲线描述,这与Towhata的理论分析成果一致,验证了本方法的合理性。分析了液化层坡度、稠度系数、流动指数以及弹性参数等变量对液化变形的影响。计算结果表明,液化变形随液化层坡度的增大而逐渐增大,液化砂土的稠度系数和流动指数对液化流动变形有重要的影响,而弹性参数对变形基本无影响,因此,在实际工程分析中,需要对流动模型参数进行深入研究。
Previous research on liquefaction flow characteristic indicates that liquefied sand can be modeled as shear thinning non-Newtonian fluid.Aflow constitutive equation of liquefied sand is established by using a power function relationship between the shear stress and the shear strain rate.A simplified method for large deformation analysis of liquefied sand is established through implementing the flow constitutive equation into the FLAC3D package.Acase study of gradient foundation is performed by applying the proposed method to validate the constitutive model.The numerical results show that the displacement of gradient foundation can be described by a sinusoidal curve,which is in good agreement with the theoretical solution of Prof.Towhata.Parametric sensitivity analyses are conducted to investigate the influences on the deformation of liquefied sand from variables including the liquefaction layer slope,consistency coefficient,flow index and elastic parameters.The results indicate that the liquefaction deformation develops with the increase of the slope of the liquefied layer.What’s more,the consistency coefficient and the flow index of the liquefied sand have significant effect on the deformation of liquefied sand;while influence from the elastic parameters is inconsiderable.A further research on these parameters should be conducted in engineering practice.
Previous research on liquefaction flow characteristic indicates that liquefied sand can be modeled as shear thinning non-Newtonian fluid.Aflow constitutive equation of liquefied sand is established by using a power function relationship between the shear stress and the shear strain rate.A simplified method for large deformation analysis of liquefied sand is established through implementing the flow constitutive equation into the FLAC3D package.Acase study of gradient foundation is performed by applying the proposed method to validate the constitutive model.The numerical results show that the displacement of gradient foundation can be described by a sinusoidal curve,which is in good agreement with the theoretical solution of Prof.Towhata.Parametric sensitivity analyses are conducted to investigate the influences on the deformation of liquefied sand from variables including the liquefaction layer slope,consistency coefficient,flow index and elastic parameters.The results indicate that the liquefaction deformation develops with the increase of the slope of the liquefied layer.What’s more,the consistency coefficient and the flow index of the liquefied sand have significant effect on the deformation of liquefied sand;while influence from the elastic parameters is inconsiderable.A further research on these parameters should be conducted in engineering practice.
引文
[1]刘汉龙.土动力学与岩土地震工程[C]//第九届土力学及岩土工程学术会议论文集.北京:清华大学出版社,2003:56-68.
[2]张建民.地震液化后地基大变形的实用预测方法[C]//第八届土力学及岩土工程学术会议论文集.北京:万国学术出版社,1999:573-577.
[3]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 sandpostliquefaction research based on fluid mechanicsmethod[J].Journal of Hohai University(NaturalSciences),2007,35(4):418-421.
[4]SASAKI Y,TOWHATA I,TOKIDA K I,et al.Mechanism of permanent displacement of ground causedby seismic liquefaction[J].Soils and Foundations,1992,32(3):79-96.
[5]MIYAJIMA M,KITAURA M,KOIKE T,et al.Experimental study on characteristics of liquefied groundflow[C]//Proceedings of The First International Con-ference on Earthquake Geotechnical Engineering.Rotterdam:A.A.Balkema,1995:969-974.
[6]MIYAJIMA M,KITAURA M.Experiments on force actingon underground structures in liquefaction-induced groundflow[J].TechnicalReport NCEER,1994,94:445-55.
[7]TOWHATA I,VARGAS-MONGE W,ORENSE R P,et al.Shaking table tests on subgrade reaction of pipe embededin sandy liquefied subsoil[J].Soil Dynamics andEarthquake Engineering,1999,18:347-361.
[8]NISHIMURA S,TOWHATA I,HONDA T.Laboratoryshear tests on viscous nature of liquefied sand[J].Soilsand Foundations,2002,42(4):89-98.
[9]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 onthe behavior of large ground displacement of sand due toseismic liquefaction[J].Chinese Journal of Geo-technical Engineering,2002,24(2):142-146.
[10]HWANG J I K C Y,CHUNG C K,et al.Viscous fluidcharacteristics of liquefied soils and behavior of pilessubjected to flow of liquefied soils[J].Soil Dynamics andEarthquake Engineering,2006,26(2-4):313-323.
[11]黄雨,毛无卫.液化后土体的流态化特性研究进展[J].同济大学学报,2011,39(4):501-506.HUANG Yu,MAO Wu-wei.State of art of fluidizationbehavior of post-liquefied soils[J].Journal of TongjiUniversity,2011,39(4):501-506
[12]黄雨,郝亮,谢攀,等.土体流动大变形的SPH数值模拟[J].岩土工程学报,2009,31(10):1520-1524.HUANG Yu,HAO Liang,XIE Pan,et al.Numericalsimulation of large deformation of soil flow based onSPH method[J].Chinese Journal of GeotechnicalEngineering,2009,31(10):1520-1524.
[13]陈育民.砂土液化后流动大变形试验与计算方法研究[D].南京:河海大学,2007.
[14]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 of flow characteristics of liquefied andpost-liquefied sand[J].Chinese Journal of GeotechnicalEngineering,2006,28(9):1139-1143.
[15]TOWHATA I,SASAKI Y,TOKIDA K I,et al.Predictionof permanent displacement of liquefied ground by meansof minimum energy principle[J].Soils and Foundations,1992,32(3):97-116.
[16]ORENSE R P,TOWHATA I.Three dimensional analysisof lateral displacement of liquefied subsoil[J].Soils andFoundations,1998,38(4):1-15.
[17]TAMATE S,TOWHATA I.Numerical simulation ofground flow caused by seismic liquefaction[J].SoilDynamics and Earthquake Engineering,1999,18:473-485.
[18]UZUOKA R,YASHIMA A,KAWAKAMI T,et al.Fluiddynamics based prediction of liquefaction induced lateralspreading[J].Computers and Geotechnics,1998,22(3/4):243-282.
[19]陈育民,徐鼎平.FLAC/FLAC3D基础与工程实例[M].北京:中国水利水电出版社,2009.
[20]陈育民,刘汉龙.邓肯-张本构模型在FLAC3D中的开发与实现[J].岩土力学,2007,28(10):2123-2126.CHEN Yu-min,LIU Han-long.Development andimplementation of Duncan-Chang constitutive model inFLAC3D[J].Rock and soil Mechanics,2007,28(10):2123-2126.
[2]张建民.地震液化后地基大变形的实用预测方法[C]//第八届土力学及岩土工程学术会议论文集.北京:万国学术出版社,1999:573-577.
[3]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 sandpostliquefaction research based on fluid mechanicsmethod[J].Journal of Hohai University(NaturalSciences),2007,35(4):418-421.
[4]SASAKI Y,TOWHATA I,TOKIDA K I,et al.Mechanism of permanent displacement of ground causedby seismic liquefaction[J].Soils and Foundations,1992,32(3):79-96.
[5]MIYAJIMA M,KITAURA M,KOIKE T,et al.Experimental study on characteristics of liquefied groundflow[C]//Proceedings of The First International Con-ference on Earthquake Geotechnical Engineering.Rotterdam:A.A.Balkema,1995:969-974.
[6]MIYAJIMA M,KITAURA M.Experiments on force actingon underground structures in liquefaction-induced groundflow[J].TechnicalReport NCEER,1994,94:445-55.
[7]TOWHATA I,VARGAS-MONGE W,ORENSE R P,et al.Shaking table tests on subgrade reaction of pipe embededin sandy liquefied subsoil[J].Soil Dynamics andEarthquake Engineering,1999,18:347-361.
[8]NISHIMURA S,TOWHATA I,HONDA T.Laboratoryshear tests on viscous nature of liquefied sand[J].Soilsand Foundations,2002,42(4):89-98.
[9]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 onthe behavior of large ground displacement of sand due toseismic liquefaction[J].Chinese Journal of Geo-technical Engineering,2002,24(2):142-146.
[10]HWANG J I K C Y,CHUNG C K,et al.Viscous fluidcharacteristics of liquefied soils and behavior of pilessubjected to flow of liquefied soils[J].Soil Dynamics andEarthquake Engineering,2006,26(2-4):313-323.
[11]黄雨,毛无卫.液化后土体的流态化特性研究进展[J].同济大学学报,2011,39(4):501-506.HUANG Yu,MAO Wu-wei.State of art of fluidizationbehavior of post-liquefied soils[J].Journal of TongjiUniversity,2011,39(4):501-506
[12]黄雨,郝亮,谢攀,等.土体流动大变形的SPH数值模拟[J].岩土工程学报,2009,31(10):1520-1524.HUANG Yu,HAO Liang,XIE Pan,et al.Numericalsimulation of large deformation of soil flow based onSPH method[J].Chinese Journal of GeotechnicalEngineering,2009,31(10):1520-1524.
[13]陈育民.砂土液化后流动大变形试验与计算方法研究[D].南京:河海大学,2007.
[14]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 of flow characteristics of liquefied andpost-liquefied sand[J].Chinese Journal of GeotechnicalEngineering,2006,28(9):1139-1143.
[15]TOWHATA I,SASAKI Y,TOKIDA K I,et al.Predictionof permanent displacement of liquefied ground by meansof minimum energy principle[J].Soils and Foundations,1992,32(3):97-116.
[16]ORENSE R P,TOWHATA I.Three dimensional analysisof lateral displacement of liquefied subsoil[J].Soils andFoundations,1998,38(4):1-15.
[17]TAMATE S,TOWHATA I.Numerical simulation ofground flow caused by seismic liquefaction[J].SoilDynamics and Earthquake Engineering,1999,18:473-485.
[18]UZUOKA R,YASHIMA A,KAWAKAMI T,et al.Fluiddynamics based prediction of liquefaction induced lateralspreading[J].Computers and Geotechnics,1998,22(3/4):243-282.
[19]陈育民,徐鼎平.FLAC/FLAC3D基础与工程实例[M].北京:中国水利水电出版社,2009.
[20]陈育民,刘汉龙.邓肯-张本构模型在FLAC3D中的开发与实现[J].岩土力学,2007,28(10):2123-2126.CHEN Yu-min,LIU Han-long.Development andimplementation of Duncan-Chang constitutive model inFLAC3D[J].Rock and soil Mechanics,2007,28(10):2123-2126.
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