汉口场地地震动特性对地下水位变化的响应

Response of Ground Motion Characteristics to Groundwater Variation in Hankou Area

以汉口城区典型中软场地钻孔剖面为对象,采用非线性土层地震反应方法,分析地下水位变化对场地地震动特性的影响。选取水平向El Centro波、Taft波和汉口人工波作为基岩输入地震动时程,分析不同地下水位对水平向峰值加速度、加速度时程、反应谱及沿土层深度最大剪应变的影响。结果表明:地下水位上升对地表水平向峰值加速度有放大效应,地下水位埋深越浅,放大效应越显著;地下水变化对加速度反应谱的0.15~1s中频段影响较大,地下水位上升,中频段成分放大效应增大;地下水位上升主要改变浅部土体性质,进而影响场地地震效应特征,但当地下水位上升至某一深度后,对土层反应影响甚微。

Based on the typical borehole profile of soft ground in Hankou,effects of groundwater variation on ground motion characteristics were analyzed by nonlinear seismic response method. The horizontal El Centro wave,Taft wave and Hankou artificial wave were selected as input bedrock acceleration. Then the influence of different ground water levels on horizontal peak acceleration,time history of acceleration,response spectrum and maximum shear strain along soil depth were evaluated. The results show that the increase of groundwater level has amplification effect on the peak ground acceleration. And The more shallow the water table,the greater the amplification effect. The variation of groundwater has obvious influence on the 0. 15 ~ 1 s band in the acceleration response spectrum, that is, with the rise of groundwater level,the amplification effect enhance in the middle frequency component. The variation of groundwater level mainly changes the properties of shallow soil,then influences the seismic effect of site,but when the groundwater level rises to a certain depth,it has little effect on seismic soil response.