岩土介质随机性对沉积河谷地震动放大效应的影

基于间接边界元法计算沉积河谷对平面P波和SV波的二维散射，着重考察沉积介质波速和材料阻尼的随机性对河谷地震动放大效应。利用蒙特卡罗方法随机模拟产生了波速样本和阻尼样本各30组，给出了不同入射角度和频率P波和SV波入射下河谷随机响应的单频和频谱结果。算例分析结果表明:(1)地表位移响应幅值的变异系数极值均显著大于波速比变异系数，且波速比的随机性对地表位移的影响在体系共振频率处最为明显，地表位移的最大标准差可达7.168；低频情况下，沉积中部地震反应变异性更显著，高频情况下则在沉积河谷边缘变异性最大；(2)入射波角度对地表位移响应变异系数极值的影响不大，但对变异系数空间变化的影响显著；(3)阻尼的随机性对地表位移的影响在低频情况下较小，在高频情况下则较明显，尤其是在沉积河谷的体系自振频率处，其影响最为显著。 

Effect of randomness of geotechnical medium on the seismic ground motion amplification effect of a sedimentary valley

Theactual geotechnical properties parameters have obvious randomness. The two-dimensional scattering of the P and SV waves in the sedimentary valleys is studied based on the indirect boundary element method (IBEM), in order to explore the effect of the randomness of the medium velocity and material damping on seismic amplification effect of valley. The Monte Carlo method is used to simulate each group of 30 wave samples and 30 damping samples randomly. Finally the present paper gives the single frequency and spectral results of random response of valley under P wave and SV wave incidence with different incident angles and frequency. The results show that the variation coefficient extremum of surface displacement response amplitude is significantly larger than the variation coefficient of velocity ratio, and the effect of velocity ratio randomness on surface displacement is most significant at system resonance frequency, and the maximum standard deviation can reach 7.168. The variation of the seismic response in the sedimentary center is more significant at low frequency, but it is the largest at the edge of the sedimentary valley at high frequency. On the other hand, the incident angle has little effect on the variation coefficient extremum of surface displacement response amplitude, but it has a significant effect on the spatial variation of the variation coefficient. Meanwhile, the damping randomness has little effect on the surface displacement at low frequencies, but the effect is obvious at high frequencies, especially at the the sedimentary valley, the effect is most significant.