回填土不确定性对场地地震反应的影响

Influence of the Uncertainty of Backfilled Soil on Site Seismic Response

选取某核电场地控制性钻孔的厚度、剪切波速、密度等实际勘探数据,通过改变回填土剪切波速,分析了回填土不确定性对场地地震动参数的影响。研究结果表明:在回填土层厚度不变和模型总厚度不变的情况下,地表的水平向峰值加速度随着回填土剪切波速的增大而减小,但水平向峰值加速度增幅逐渐减小;回填土剪切波速到达一定的波速就不再影响地表水平峰值加速度;随着回填土剪切波速的增加,整个反应谱的谱值都普遍减小。

Ground motion characteristics are relatively affected by the local conditions of the site,and the site often needs backfill and foundation treatment before construction.Therefore,it is necessary to study the influence of the backfilled layer on the seismic response of the site.In this paper,we analyzed the two-dimensional seismic response of a nuclear power site with the software MIDAS GTS NX,i.e.,thickness,shear wave velocity,and density of controlled boreholes at the site.Time histories of input ground motion have a great impact on ground motion parameters,thus the results of these parameters can vary significantly.To maximize the response of the structure and narrow the gap between earthquake action on the structure and the actual earthquake action,five time-history samples were fitted as the input seismic ground motion,and three models with different shear wave velocities of backfilled soil layer were established.The results showed that,with constant thickness of backfilled soil and constant total thickness of the model,the horizontal peak acceleration of the surface decreases with increasing shear wave velocity of the backfilled soil,but the amplitude was gradually reduced.The surface horizontal peak acceleration will no longer be affected when the shear wave velocity reaches a certain value.We also found that with increasing shear wave velocity of backfilled soil,the spectral value of the entire response spectrum will generally decrease.