成层场地地震波动输入模式研究

Study on the seismic wave input mechanism in layered site

当前应用时域方法分析水工结构-地基动力相互作用分析是研究热点,但成层场地条件下地震波动输入模式研究较少。通过研究地震波在成层场地波动传播规律,推导了SH波在层间分界面处发生反射和透射的系数公式,之后将其应用于粘弹性人工边界模型改进了传统等效荷载输入模式。改进后的波动输入模式考虑了各层间波动传播速度的不同及层间分界面处波动振幅和相位改变,从而解决了传统等效荷载输入模式求解成层地基时两侧与内部节点波动传播不一致的问题。算例表明该方法具有良好的精度和稳定性,同时结果表明相同的底部波动输入成层自由场表面振动幅值大于均质自由场。

The time - domain analysis method is a research hotspot for hydraulic structure foundation dynamic interaction. However, there are fewer studies on the wave input mechanism under stratified site condition. By studying the wave propagation law of seismic wave in stratified field, the coefficient formula of SH wave reflection and transmission at the interface between layers is derived, and then it is applied to viscoelastic artificial boundary model to improve the traditional equivalent load input mode. The improved seismic input mode takes into account the difference of wave propagation velocity between layers and the change of undulation amplitude and phase at the interface between layers,so as to solve the problem that the wave propagation between two sides and internal nodes is in-consistent when the traditional equivalent load input mode is used to solve the problem of layered foundation. Numerical examples show that the proposed method has good accuracy and stability, and the results show that the surface vibration amplitude of the layered free field with the same bottom fluctuation input is greater than that of the homogeneous free field.