珊瑚岛礁海域场地地震反应分析

Seismic Response Analysis of a Coral Island in Sea Area

基于南海某岛礁的实际工程地质剖面图建立了海水-岛礁-地震耦合的岛礁模型,利用FLAC有限差分方法,分析了是否考虑海水作用2种情况下水平输入海底地震动时岛礁的场地地震反应规律。结果表明:①灰砂岛PGA放大效应显著,灰砂岛及外礁坪角点处PGA放大效应取得极大或极小值;②考虑流固耦合及岛礁外部海水动力作用后,岛礁场地地震反应呈现与不考虑海水作用基本持平或降低的趋势;③岛礁水平向加速度放大系数整体随输入地震动峰值的增大而减小,随着砂层深度的减小总体呈增大趋势。

Based on the actual engineering geological profile of a coral island in the South China Sea,a two-dimensional island model with seawater-island-seismic coupling is established.The FLAC finite difference method is used to analyze the seismic response of islands when horizontal input seafloor ground motions are considered in the two cases.The results show that:①The PGA amplification effect at lime-sand island is significant,and the PGA amplification effect at the corner point of the lime-sand island and outer reef have achieved a maximum or minimum value;②Compared with ignoring seawater effects,after considering the fluid-solid coupling of seawater and the dynamic effects of seawater outside the islands,the seismic response of the islands show a flat or decreasing trend;③The amplification factor of the horizontal acceleration of the island decrease with the increase of peak value of the input earthquake and generally increase as the decrease of the sand layer depth.