深厚覆盖层上土石坝动力分析黏弹性边界处理方法

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。

Visco-elastic boundary processing method for dynamic analysis of earth-rock fill dam on deep overburden layer

In the dynamic analysis of earth-rock fill dam on deep overburden layer, the foundation of dam is truncated usually when the depth of overburden layer is higher than the height of dam on it, and the analysis object is the system of dam and its near-field foundation.The problem that dam response becomes larger because of the boundary truncation can be solved effectively though the application of visco-elastic boundary condition in dynamic analysis of the dam-foundation system.Dynamic response analysis method of the earth-rock fill dam on deep overburden layer base on visco-elastic boundary condition is established in the paper.The problem of seismic motion input under visco-elastic boundary condition is solved by the method of applying equivalent seismic inertia force on structures.Dynamic nonlinear characteristics of soil is reflected using the equivalent linearization method.The results show that, the problem of seismic motion input under visco-elastic boundary condition can be solved effectively by the method of applying equivalent seismic inertia force on structures, and the dynamic response levels of dam in earthquake is increased when the cut-off boundary of dam is fixed, which makes the calculated results conservative.