地震作用下含倾斜软弱夹层斜坡场地的动力响应特性研究

Dynamic responses of slopes with intercalated soft layers under seismic excitations

以四川北部龙门山断裂带附近山区内某核废料处置场为参考原型,概化出含软弱夹层的斜坡场地模型,设计完成该特殊场地在50倍重力加速度条件下的离心振动台模型试验,监测场地在不同输入地震工况下的加速度响应,重点通过加速度放大效应和地震波波动机制探讨软弱夹层和斜坡效应对斜坡场地动力响应的影响,此外,结合传统傅里叶谱和Hilbert边际谱方法,从频域角度展示场地的频谱变化特性。试验结果表明:软弱夹层的加速度放大效应与输入地震动峰值有关,当输入地震动峰值较小时,夹层内响应加速度峰值被削弱,当输入峰值较大时,则被增强;斜坡效应对该场地中软弱夹层内的动力响应存在影响,导致斜坡下的软弱夹层内加速度放大效应增强;随着输入地震动峰值增大,软弱夹层中响应加速度的频率成分发生了变化,高频成分减少而低频成分增加。

A slope model with inclined soft layers intercalated was generated to simulate a slope site fornuclear waste disposal near to Longmenshan fault zone in northern Sichuan province and the centrifugal shaking table test of 50 g was carried out. The accelerations of the model under different input ground motions triggered by earthquakes were measured. The traditional Fourier spectrum and Hilbert marginal spectrum were utilized to reveal the variation of spectral characteristics of the slope in frequency domain. The experimental results show that the acceleration amplification of the intercalated soft layers was related to the peak input seismic acceleration. The acceleration amplification was weakened under the smaller peak input seismic acceleration,but was strengthened under the larger seismic ground motions. The slope has marked influence on the dynamic responses of the intercalated soft soil layers in this site. The slope caused the acceleration amplification of the intercalated layers to increase. With the increasing of peak input seismic motion,the components of acceleration response at the intercalated soft layers were changed,the higher frequencies decreased but lower components increased.