超大型地下洞室群的随机地震响应分析

地下结构的地震响应分析由于结构-围岩的动力相互作用及地震动输入的不确定性而十分复杂，尤其是对空间尺度很大的大型水电站的超大型地下厂房洞室群，地震动输入的空间变化特性将对结构的地震动响应产生重要的影响。本文首先通过阻尼影响-抽取法求出地下结构无限围岩介质的动阻抗，在此基础上通过考虑地震动输入空间变化的随机过程模型，采用随机分析方法研究了地震动输入机制对地下洞室群动力响应的影响。结果表明，地震波的行波效应、空间相干性损失及散射效应是影响地下结构动力响应的关键因素。考虑地震波的行波效应和空间相干性损失可以使地下结构的地震响应降低，但是地震波的散射效应可以增大地下结构的地震响应，结构的动力响应分析必须综合考虑这几项影响。

Random seismic response analysis of large scale underground caverns

The seismic analysis of large scale underground caverns is complicated because of the interaction between structure and surrounding rocks and the uncertainty of earthquake excitation. Besides, the spatial variation characteristics of earthquake excitation have great effects on seismic response of the structures. In this paper, the dynamic impedance of surrounding rocks is evaluated using the damping solvent method. On this basis, the effect of the uncertainty of seismic input on dynamic random response of large scale underground caverns is studied using pseudo excitation random method. The results show that the seismic spatial coherence loss, wave travelling and scattering around the caverns may significantly affect the seismic response of underground caverns. The seismic wave travelling effect and spatial coherence loss will reduce the seismic response of underground structures, whereas the wave scattering effect can greatly improve the dynamic response of the underground structures. These factors must be taken into accoun in seismic analysis of the structures.