深厚覆盖层上土石坝动力分析黏弹性边界处理方法
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摘要
当覆盖层地基深度相对其上土石坝坝高较大时,大坝动力分析计算中常将覆盖层地基截断,只取临近坝体部分覆盖层地基连同坝体一起作为计算分析对象。用黏弹性边界条件代替固定边界条件,可以消除或有效降低由于截断边界造成外行波无法透过边界而引起的计算误差。本文采用施加等效地震惯性力的方法实现黏弹性边界条件下的地震动输入、采用等效线性化方法反映覆盖层地基边界上黏弹性边界条件的非线性特性,建立了基于黏弹性边界条件的深厚覆盖层上土石坝动力反应分析方法。研究表明:施加等效地震惯性力的方法可以简单而有效地解决黏弹性边界条件下的地震动输入问题;固定边界条件大幅提高了坝体在地震作用下的动力反应水平,使得计算的结果偏于安全。
In the dynamic analysis of earth-rock fill dam on deep overburden layer,the foundation of damis truncated usually when the depth of overburden layer is higher than the height of dam on it,and theanalysis object is the system of dam and its near-field foundation. The problem that dam response becomeslarger because of the boundary truncation can be solved effectively though the application of visco-elasticboundary condition in dynamic analysis of the dam-foundation system. Dynamic response analysis method ofthe earth-rock fill dam on deep overburden layer base on visco-elastic boundary condition is established inthe paper. The problem of seismic motion input under visco-elastic boundary condition is solved by themethod of applying equivalent seismic inertia force on structures. Dynamic nonlinear characteristics of soilis reflected using the equivalent linearization method. The results show that,the problem of seismic motioninput under visco-elastic boundary condition can be solved effectively by the method of applying equivalentseismic inertia force on structures, and the dynamic response levels of dam in earthquake is increasedwhen the cut-off boundary of dam is fixed,which makes the calculated results conservative.
In the dynamic analysis of earth-rock fill dam on deep overburden layer,the foundation of damis truncated usually when the depth of overburden layer is higher than the height of dam on it,and theanalysis object is the system of dam and its near-field foundation. The problem that dam response becomeslarger because of the boundary truncation can be solved effectively though the application of visco-elasticboundary condition in dynamic analysis of the dam-foundation system. Dynamic response analysis method ofthe earth-rock fill dam on deep overburden layer base on visco-elastic boundary condition is established inthe paper. The problem of seismic motion input under visco-elastic boundary condition is solved by themethod of applying equivalent seismic inertia force on structures. Dynamic nonlinear characteristics of soilis reflected using the equivalent linearization method. The results show that,the problem of seismic motioninput under visco-elastic boundary condition can be solved effectively by the method of applying equivalentseismic inertia force on structures, and the dynamic response levels of dam in earthquake is increasedwhen the cut-off boundary of dam is fixed,which makes the calculated results conservative.
引文
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[14]尚守平,卢华喜.土波动问题中基于动模量衰减的人工边界[J].湖南大学学报,2005,32(6):18-23.
[15]卢华喜,梁平英,尚守平.地基非线性波动问题中黏-弹性人工边界研究[J].岩土力学,2008,21(4):1911-1916.
[2]杜修力,赵密,王进廷.近场波动模拟的人工应力边界条件[J].力学学报,2006,38(1):49-56.
[3]LIAO Z P,WONG H L.A transmitting boundary for numerical simulation of elastic wave propagation[J].Soil Dynamics and Earthquake Engineering.1984,3(4):174-183.
[4]LYSMER J,KUHLEMEYER R L.Finite dynamic model for infinite media[J].Journal of engineering mechanics division.ASCE.1969,95(4):759-877.
[5]DEEKS A J,RANDOLPH M F.Axisymmetric time-domain transmitting boundaries[J].Journal of Engineering Mechanics.ASCE.1994,120(1):25-42.
[6]刘晶波,吕彦东.结构-地基动力相互作用问题分析的一种直接方法[J].土木工程学报,1998,31(3):55-64.
[7]刘晶波,王振宇,张克峰,等.考虑土-结构相互作用大型动力机器基础三维有限元分析[J].工程力学,2002,19(3):34-38.
[8]刘晶波,王振宇,杜修力,等.波动问题中的三维时域黏弹性人工边界[J].工程力学,2005,22(6):46-51.
[9]王立涛,陈厚群,马怀发.人工黏弹性边界的接触非线性问题在FEPG中的实现[J].水力发电学报,2009,28(5):179-181.
[10]马怀发,王立涛,陈厚群.粘弹性人工边界的虚位移原理[J].工程力学,2013,30(1):168-174.
[11]IDRISS I M,LYEMER J,HWANG R,et al.QUAD-4:a computer program for evaluating the seismic response of soil structures by variable damping finite element procedures[R].Berkeley:University of California,Berkeley.1973.
[12]刘颖,谢君斐.砂土震动液化[M].北京:地震出版社,1984.
[13]楼梦麟,李强.关于结构系统地震输入模式问题的讨论[J].世界地震工程,2004,24(2):21-25.
[14]尚守平,卢华喜.土波动问题中基于动模量衰减的人工边界[J].湖南大学学报,2005,32(6):18-23.
[15]卢华喜,梁平英,尚守平.地基非线性波动问题中黏-弹性人工边界研究[J].岩土力学,2008,21(4):1911-1916.