超深厚覆盖层上土石坝动力分析边界处理方法研究

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

采用深厚覆盖层上土石坝动力分析黏弹性边界处理方法和传统固定边界处理方法,进行某超深厚覆盖层上土石坝动力反应分析,研究了边界处理方式和地基截断范围对大坝-地基系统动力反应分析计算结果的影响规律,探讨了超深厚覆盖层上土石坝结构-地基系统动力分析边界处理方法。研究表明:不同的边界处理方式,大坝-地基系统内部加速度反应的分布规律基本一致,黏弹性边界条件下的坝体地震动力反应水平低于固定边界;随着覆盖层地基侧向边界范围的扩大,不同边界条件下坝体的加速度反应水平都在降低,固定边界条件下的计算结果和黏弹性边界逐步趋近;对本文研究的超深厚覆盖层上土石坝结构-地基系统,动力分析中将底部边界取到基岩表面、侧向边界取到坝踵和坝脚向上下游延伸3~5倍大坝加地基高度范围,并采用固定边界的边界处理方式,可以达到工程设计对计算精度的要求。

In this paper,the visco-elastic boundary processing method for dynamic analysis of earth-rock fill dam on deep overburden layer and the traditional fixed boundary processing method were used to do the dynamic response analysis of one earth-rock fill dam on super-deep overburden layer under earthquake. The influencing law of boundary processing way and foundation cut-off scale on dynamic analysis results was studied firstly,and the boundary processing method of dam and foundation system which is the study subject in this paper was investigated carefully then. The results show that,the distribution law of acceleration response in dam and foundation system is consistent basically in different boundary processing ways. Dynamic response level of dam in visco-elastic boundary condition is lower than it in fixed boundary condition,and the calculation results in fixed boundary condition is somewhat safe. The acceleration response level of dam declines in different boundary processing ways as the increasing of overburden layer foundation scale,and the calculation results in fixed boundary processing way and visco-elastic boundary processing way tend to closed when the foundation scale is large enough. For the earth-rock fill dam and foundation system in this paper,the reasonable boundary processing method of system dynamic analysis is that the interface of deep overburden soil layer and base-rock is selected to be the bottom boundary,two lateral cut-off boundaries are 3-5 times of dam and foundation height from two dam feet,and the boundary processing way is the fixed boundary condition.