地震和波浪作用下表面波条件对海水动水压力的影响

地震动斜入射条件下海洋场地简化为理想流体海水-两相介质海床-弹性固体基岩系统模型,通常假定为静水液面条件。本文以地震动SV波为例,推导了表面波条件下海洋场地动力反应解析解,研究了表面波条件对海水动水压力的影响。研究表明,表面波频率在大于0.5Hz时对海水动水压力几乎无影响,在小于0.5Hz范围内有影响,且越接近水面、频率越低时影响越显著。实际地震动卓越频率通常大于0.5Hz,因而地震动作用下采用忽略表面波条件的静水液面假定是合理的。进一步结合线性波浪理论,研究SV波和波浪联合作用下表面波条件对海水动水压力的影响。研究表明,由于波浪属于低频荷载且频率通常小于0.5Hz,在地震和波浪联合作用下表面波条件的影响较地震单独作用更为显著。

The Influence of Surface Wave Condition on Hydrodynamic Pressures of Seawater under Earthquake and Waves

The ocean site is usually simplified as the seawater-seabed-bedrock system under the obliquely incident earthquake, where the seawater is ideal fluid, the seabed is poroelastic media, and the bedrock is elastic solid. In this paper, the analytical solution to the dynamic responses of the ocean site with the surface wave condition is derived. The influence of the surface wave condition on the ground motion hydrodynamic pressures of seawater is studied. Our results show that when the frequency is higher than 0.5 Hz, the surface wave condition is almost no effect. If the frequency is lower than 0.5 Hz, the effect is significant. The closer to the surface position and the lower frequency will enhance such effect. Because the excellent frequency of actual ground motion is generally larger than 0.5 Hz, the assumption of the rest surface condition is reasonable. However, since the wave is low frequency load and its frequency usually is less than 0.5Hz, the effect of the surface wave condition is more significant under the action of earthquake and wave than under only earthquake.