【摘要】 假定土层为线性粘弹性介质,在频域内采用有限元法分析了均匀土层中有限土域的取值范围对计算精度的影响。在一致输入作用下,主要探讨了土层地震反应随不同侧向人工边界、迫振频率、阻尼和土层长深比的变化规律。在此基础上,得到直接有限元法进行土层地震反应分析的经验计算范围。最后对一河谷地形的土层进行地震反应分析,计算表明在进行土层地震反应分析时,采用本文土层范围取值来确定土域的计算范围可以得到满意的结果。为在应用直接有限元法进行土层地震反应计算时,确定有限土域范围提供依据。更多还原

【Abstract】 When applying direct Finite Element Method(FEM) to analyze seismic response of soil layer,finite region of soil layer is used approximately to simulate the half-infinite soil layer.In order to eliminate the influence of the artificial boundary on the seismic response of soil layer,several different types of artificial boundaries were developed.Usually these artificial boundaries were based on the assumption that the dynamic exciting source is located in the analytical soil region.However,in the problem of seismic response analysis of soil layer by direct FEM,the seismic source is out of the soil region.Therefore,the influences of the artificial boundary on the seismic response of the soil layer include not only the wave reflection on the artificial boundary but also the reduction of excitation scope.It is a more complicated problem.In this paper,the effects of some artificial boundaries,such as free boundary and Lysmer’s viscous damping boundary,are studied.Several influence parameters such as exciting frequency,soil damping and the ratio between width and depth of the cut soil layer is discussed by numerical examples based on linear visco-elastic assumption.From numerical results,it is concluded that the ratio between width and depth of the cut soil layer is the major influence parameter to determine the scope of soil layer and viscous damping boundary is not effective in the problem discussed in this paper.The reasonable ratio between width and depth of the cut soil layer is suggested.Based on above conclusion,the response of a river-crossing topography under seismic excitations was analyzed.The results showed that the scope of cut soil layer is satisfied.更多还原