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场地土的特性是影响场地地震反应的重要因素。以往自由场地震反应分析中常假定场地土为单相介质或两相饱和多孔介质,而在实际工程中,常会遇到非饱和土的相关问题。目前对非饱和土波动特性的研究尚处于起步阶段,关于土体饱和度的变化对自由场地地震动的影响亦只针对准饱和土(饱和度Sr≥90%)的情况。为研究Sr<90%时,饱和度变化对自由场地地震动的影响,建立了非饱和土自由场地地震反应分析模型,在现有的非饱和多孔介质波动方程的基础上,对平面P波入射情况下场地中的波场进行分析,根据场地边界条件,求得到平面P波入射情况下非饱和土自由场地地震地面运动的解析解答,通过计算,系统地分析了入射角度、频率、土层刚度、孔隙率不同时,土体饱和度变化对非饱和土自由场地地震地面运动的影响,得到了非饱和土自由场地地震反应的一般规律。
The characteristic of site soil is an important factor that affects the earthquake response of the site. Earthquake response analysis of free field in the past often assumes that the site soil is a single-phase medium or two-phase saturated porous media, and in practical projects, often encounter problems related to unsaturated soil. At present, the research on the fluctuating characteristics of unsaturated soils is still in its infancy, and the influence of the change of soil saturation on the free-field ground motions is only for quasi-saturated soils (saturation Sr≥90%). In order to study the effect of saturation change on free ground ground motions when the Sr <90%, the seismic response analysis model of free ground in unsaturated soil is established. Based on the existing wave equation of unsaturated porous medium, According to the boundary conditions of the site, the analytic solution of the earthquakes in the free-field of unsaturated soil under the incident plane P-wave is obtained. By means of calculation, the incident angle, frequency, soil stiffness , Different porosity, soil saturation changes on the unsaturated ground motion of free-field ground motion, get the general rules of the unsaturated earth free-field seismic response.