雨水浸润软化下路基土质边坡浅层稳定分析

摘要

在雨水浸润软化引起边坡浅层失稳的"顺坡平面"和"顺坡折线"两种破坏模式基础上,明确边坡浅层溜坍呈现组合式"顺坡曲面"失稳模式;基于Mohr-Coulomb强度理论,建立雨水浸润软化土体达到破坏的判别方程,导出顺坡向滑动的主滑区滑体产生剩余下滑力对应的最小软化深度zcr,论证软化深度zw=zcr仅是产生浅层失稳破坏的必要条件,充分条件还须考虑上下缘滑体的力学作用;确定对数螺旋线滑体上下缘滑动面形态,提出满足上下缘滑体力矩平衡、中段主滑体静力平衡的土质边坡浅层稳定分析方法.分析表明:浅层边坡失稳的主滑区范围L2随zw呈双曲线衰减关系,在L2=0对应的最大浸润软化深度zf下,滑动面退化为具有对数螺旋线型特征的单一整体滑面破坏模式.%On the basis of two failure modes of the "parallel slope-plane" and "parallel slope-polyline" caused by rainwater wetting and softening, the "parallel slope-curved surface" failure mode of shallow slope collapse has been defined.Based on Mohr-Coulomb theory, the discriminant equation of soil to reach the damage state by rainwater infiltration has been established.The minimum softening depth zcr, corresponding to the residual sliding force generated by the slip mass of the main slide zone when the slip mass slips along the slope, has been derived.It is proved that the softening depth zw=zcris only the necessary condition to reach shallow slope fai-lure.For sufficient conditions of shallow failure, the mechanical effects of the upper and lower edges of the slip mass should be taken into account.The sliding surface of the upper and lower edges of the logarithmic spiral body was determined.The soil slope shallow stability analysis method was proposed, which meets the moment balance of the upper and the lower edges of the slip mass, and static force balance of the middle section of the slip mass.The analysis showed that the main sliding zone of shallow slope instability L2 showed hyperbolic attenuation relation with zw, under maximum softening depth zf corresponding to L2=0, the slip surface degradation became single integral sliding surface failure mode with logarithmic spiral characteristics.