饱和土体-地下综合管廊结构地震响应分析

将土体视为固-液两相介质,基于饱和土体有效应力原理,建立饱和土体-地下综合管廊结构体系相互作用动力模型:在地应力平衡的静力状态下采用Duncan-Chang非线性弹性本构模型,在地震波作用的动力状态下采用Davidenkov非线性黏弹性本构模型;考虑饱和土体黏弹性动力人工边界条件,将地震动作用转化为作用在人工边界节点上的动力荷载。模型考察不同地震波时程、地震波加速度峰值、入射角度、孔隙率以及地应力场的影响,得出如下结论:(1)地震波的卓越周期与场地卓越周期相近时引起结构上的变形最大;随着地震波加速度峰值的增大结构变形增大;随着地震波入射角度的增加结构变形增大,地震波斜入射情况下产生的行波效应使得结构变形最大。(2)土体材料的孔隙水压力是影响地震中结构变形的主要因素之一。(3)将土体材料考虑为单相介质时结构上的变形要比考虑为固-液两相介质时大得多,直接将饱和土体场地中得到的地震波等效荷载施加到单相土介质-结构动力相互作用模型上,能够得到与完全基于有效应力法一致的结果。

Seismic Response of Underground Utility Tunnel Structures in Saturated Soils

Based on the effective stress principle of saturated soil, a dynamic model for saturated soil-underground utility tunnels (UUT) interaction is presented. During modeling, the soil was considered as a solid-liquid two-phase media, and the Duncan-Chang constitutive model was used under statistic load, while the Davidenkov model was used when the tunnels were subjected to the action of seismic waves. The viscous-elastic artificial boundary condition of saturated soil was considered, and the ground motions were translated into dynamic load applied to the artificial boundary nodes. The influences of time histories, PGAs, incidence angles of input earthquake waves, porosity of soil, and ground stress fields on the seismic response of UUT were investigated. The following conclusions were drawn from the above analysis:(1) The deformation of structure reaches a maximum when the predominant period of an earthquake wave is close to that of the site, and the deformation of structure increases with increasing PGA and incidence angle of the seismic wave; (2) pore water pressure in the soil is one of main influencing factors in structure deformation; (3) the deformation of structure in single-phase media is much larger than in two-phase media, and the results, based on effective stress methods, were in accord with those based on single-phase media and structure dynamic interaction models subjected to the equivalent load of earthquake waves in saturated soils.