非均质土坡降雨入渗的耦合过程及稳定性分析

Rainfall infiltration coupling process and stability analysis of a heterogeneous soil slope

针对天然土质边坡通常呈现非均质特性这一问题,进行了降雨入渗作用下非均质土坡稳定性分析,考虑了渗流场和应力场之间的耦合作用。以一简化非均质土坡模型为例,对比了耦合和非耦合情况下渗流场的差异,验证耦合的客观性和其必要性;细-粗型和粗-细型土坡的降雨入渗过程可分别分为2个和3个阶段;运用有限元强度折减法,以特征部位位移突变并结合塑性区贯通作为失稳判据,进行了土坡稳定性分析,发现雨水到达土坡土层接触面的时刻即为边坡稳定性突变的时刻;并通过深入分析孔隙水压力分布,揭示了降雨诱发非均质土坡的变形破坏机制。同时,就降雨强度、历时和渗透系数对非均质土坡入渗过程和稳定性的影响进行了大量的计算和分析,发现只有当雨水进入到下层土体时,该层土体渗透系数才会对土坡稳定性产生较大影响。

There usually occur heterogeneous characteristics for natural soil slopes.This paper conducts the heterogeneous soil slope stability under rainfall infiltration and takes the coupling effect of seepage field and stress field into account.The difference between coupling and uncoupling is compared by a simplified heterogeneous soil slope example.The results show that the coupling analysis is more practical and feasible.The rainfall infiltration process of fine-coarse type slope and coarse-fine type slope can be divided into two and three stages separately.Finite element strength reduction is employed to analyze soil slope stability of different rainfall intensity and duration based on the displacement mutation as the instability criterion combined with the plastic zone.It is found that the moment that water reaches the soil contact surface is exactly the moment that the slope stability mutations.Rainfall-induced heterogeneous soil slope deformation and failure mechanisms are revealed by in-depth analysis of pore water pressure distribution.A large number of calculations and analyses are conducted by analyzing the effect of rainfall intensity,duration and permeability coefficient on the infiltration process and stability.The results indicate that only when the rain water reaches the subsoil,the layer of soil permeability coefficient will have a greater impact on slope stability.