地表水下渗对典型黄土场地地震效应的影响

Effect of surface water permeation on earthquake response of loess sites

近年来,地表水下渗对工程地质灾害的影响逐渐被人们所关注,但是其对黄土场地地震动的影响还没有引起足够的重视。因此,选取典型黄土场地,分析了地表水下渗对地表加速度反应峰值及加速度反应谱的影响,旨在研究地表水下渗对黄土场地地面运动的影响规律。结果表明:随着地表水的不断下渗,地表地震峰值加速度及土层地震动放大作用都有减小趋势,地表水的存在一定程度上对地震动具有减震作用;但场地的特征周期都有增的趋势,反应谱平台范围越来越宽,使得地面上固有周期处于反应谱平台范围内的建筑都有较大的反应,尤其是与原始剖面(没有地表水)相比,地表水的存在对场地特征周期的放大作用最大可达1.5倍左右,这使得地面上更多的建筑都会有较大的反应。

In recent years, engineering geological disasters induced by surface water permeation have gradually been concerned. However, enough attention has not been paid to the influence of surface water permeation on ground motion. In order to study the influence of surface water permeation on ground motion in loess area, this paper selects a typical loess site and analyzes the effect of surface water permeation on peak ground acceleration and acceleration response spectrum. The following conclusions are obtained：the lower the surface water level is, the less the peak ground acceleration and amplification factor. The existance of surface water can reduce the ground motion to a certain extent. But, the characteristic period of site become longer, the platform of response spectrum becomes wider. This will make buildings with natural period in width of platform have large response. In particular, compared with the original profile （no surface water）, surface water can amphfy characteristic period up to about 1.5 times, which makes more buildings have larger response.