饱和层状场地中任意凹陷地形对入射SV波的散射  

SV wave scattering by a canyon of arbitrary shape in a saturated layered half-space

作　　者：尤红兵 梁建文[2] 赵凤新 

机构地区：[1]中国地震灾害防御中心,中国北京100029 [2]天津大学土木工程系,中国天津300072

出　　处：《地震学报》2011年第6期735-745,843,共11页Acta Seismologica Sinica

基　　金：国家自然科学基金(50978183);地震行业科研专项(200708034)共同资助

摘　　要：利用饱和土层的精确动力刚度矩阵和动力格林(Green)函数,采用间接边界元法,在频域内求解了层状饱和场地中任意凹陷地形对入射SV波的散射问题.通过自由场反应分析,求得凹陷地形表面各点的位移和各单元的应力响应;同样计算了虚拟分布荷载的格林影响函数,求得相应的位移和应力响应;根据边界条件确定虚拟分布荷载,将自由场位移响应和虚拟分布荷载产生的响应叠加得到了问题的解答.本文方法可进行退化,所得结果与不含孔隙水的干土结果一致.对3种饱和场地自由场反应和凹陷地形对入射SV波散射进行分析,并与相应干土结果进行了对比.研究表明,入射角度、入射频率、粘性耦合系数等对地表位移有重要影响.在饱和场地中,入射波频率和粘性耦合系数(土的渗透性)影响土层中波的传播速度,导致地表位移幅值与干土场地产生明显差异,尤其是入射角在30°—60°范围内.因此,在饱和场地动力分析中应综合考虑入射角度和入射频率对场地地表位移的影响.Based on exact dynamic-stiffness matrices and Green＇s functions of a layered saturated soil,the scattering of SV waves by a canyon of arbitrary shape in a saturated layered half-space is modeled using the indirect boundary element method in frequency domain.The free-field responses are calculated to determine the displacement and stress at canyon surface,and fictitious distributed loads are then applied on the canyon surface in the free field to calculate the Green＇s functions for displacement and stress.The amplitude of the fictitious distributed loads are determined from the boundary conditions,and the displacements arising from the waves in the free field and from the fictitious distributed loads are summed to obtain the solution.The present method can be degenerated and the result agrees well with that of dry soil without fluid.The free-field responses of three different saturated sites are calculated and numerical results for displacements of the canyon due to incident SV waves are presented.The results of the saturated sites are compared with that of corresponding dry layered site.It is shown that the incident angle,the frequency of incident wave and penetrability of soils have a great effect on displacements.The frequency of incident wave and the internal friction parameter or the penetrability of soil influence the velocities of three waves propagated in layered saturated soils,which result in the apparent difference between the saturated layered half-space and the dry site,especially for the incident angles from 30° to 60°.The incident angle and frequency of incident wave should be comprehensively considered in dynamic analysis of the saturated sites.

关 键 词：饱和层状半空间 任意凹陷地形 SV波 散射 

分 类 号：TU433[建筑科学—岩土工程]