海底软土层对海洋地基场地动力响应的影响

Study of the seismic response of the seafloor ground containing soft soil

利用波动分析法,建立了海水-成层饱和土-基岩3种介质耦联系统的波场方程,推导了平面P波和SV波入射时,海洋地基场地位移解析表达式,通过数值算例重点研究了不同水深下,海底软土层的厚度及埋深对水土交界面处位移的影响规律。结果表明:当P波入射时,对于同一水深和软土层埋深,软土层会显著地放大水平及竖向位移峰值,在同一软土层埋深下,水平及竖向位移峰值和共振频率均不与软土层的厚度及水深存在单调增加的关系;当SV波入射时,在同一软土层厚度和埋深下,水深对水平及竖向位移峰值和共振频率的影响均较小,对于同一水深和软土层埋深,软土层会显著地放大水平位移峰值,对竖向位移的影响较小。

Based on wave theory and displacement potentials,wave field equations of plane P and SV wave for seafloor ground are developed.The seafloor ground is composed of seawater layer,bedrock,and stratified saturated soil layers with seafloor soft soil in this paper.The effects of thickness and position of soft soil on the displacement at the water-soil interface under different seawater depths are explored by numerical examples.The results show in the case of the same depth and position,soft soil can significantly amplify the peak value of horizontal and vertical displacement,and the peak value and resonant frequency of horizontal and vertical displacement do not monotonically increase with the soft soil thickness and seawater depth under P-wave incidence.For the same thickness and position of soft soil,seawater depth barely affects the peak value and resonant frequency of horizontal and vertical displacement.Furthermore,soft soil can significantly amplify the peak value of horizontal displacement and affect subtly on the peak value of vertical displacement under SV-wave incidence.