【摘要】 场地条件对地震地面运动的影响很大,而对于黄土地区地震地面运动规律又有其自身的特性。鉴于兰州市区地下水位的不断上升,本文选取典型黄河南岸Ⅱ级阶地黄土场地,假设水位逐次提高1m,通过土层地震反应分析计算,分析地下水位上升对地表峰值加速度及反应谱的影响。结果表明:随着地下水位的不断上升,地表峰值加速度及土层地震动放大作用都有减小趋势,地下水的上升一定程度上对地表加速度峰值具有减震作用;但场地的特征周期却有增大趋势,平台范围越来越宽,反应谱双峰现象越来越显著,尤其当水位上升较多(文中11m),在罕遇地震动作用下对所有结构物加震显著,在常遇地震动和设计地震动作用下对自振周期0.7～1.3s结构物加震明显,应引起重视。更多还原

【Abstract】 The effect of site conditions on earthquake ground motion is remarkable,and the earthquake ground motion in loess region has its own characteristics.In view of the rising groundwater of Lanzhou,this paper selects a typical loess site on second terraces of Yellow River,supposes groundwater will rise 1m one time,and analyzes the effect of groundwater rise on peak ground acceleration and acceleration response spectrum by soil seismic response analysis.The following conclusions can be drawn:the higher the groundwater level,the less the peak ground acceleration and amplification factor will be.Groundwater rise can reduce the effect of ground motion to a certain extent.But the characteristic period becomes longer,the flat portion of response spectrum becomes wider,and the two-peak phenomena are more significant.Especially when the groundwater rises more(11m in this paper),the accelerations of the loess site amplify significantly under seldom occurring ground motions,the accelerations of the structures on the loess site,the natural periods of which are in the range of 0.7～1.3 s,increase under frequently occurring ground motions and design ground motion.Attention should be paid to this.更多还原