降雨入渗对非饱和土体边坡稳定性影响及治理对策

为研究降雨入渗对非饱和土体边坡稳定性影响，基于饱和—非饱和渗流理论，分析了降雨入渗条件下边坡内部渗流场变化及其对边坡稳定性的影响。研究表明：①降雨入渗是饱和—非饱和过程，其内部体积含水率随降雨持续时间的变化而发生动态改变，在降雨初期，土体处于非饱和状态，黏聚力随着含水率的增大而增大，内摩擦角变化幅度较小，总体呈下降趋势，基质吸力增强，安全系数升高，对边坡稳定性有利；②随着降雨持续，孔隙水压力由负变正，黏聚力和内摩擦角随着含水率的增大而减小，基质吸力减弱，边坡稳定性降低；③降雨入渗终态过程为内部水位线升高，动静水压增加，土体有效重度降低，土体发生软化，力学强度参数降低，边坡稳定性随之降低，土体渗透系数与边坡安全系数总体成反比关系。在上述分析的基础上，结合土质边坡实例，应用强度折减法，分析了降雨入渗状态下边坡潜在滑动面、峰值位移随降雨持续时间的变化规律，认为降雨初期潜在滑动面由浅入深，峰值位移不断增大；降雨停止后，土体内部应力重新分布，土体由饱和转为非饱和，潜在滑动面、峰值位移发生逆变化。为防止降雨条件下边坡发生失稳破坏，针对性地提出了土质边坡治理建议，为非饱和土体边坡综合治理提供了有益参考。

Influence of Rainfall Infiltration to the Stability of Unsaturated Soil Slope and Its Countermeasures

In order to study the influence of rainfall infiltration on the stability of unsaturated soil slope，based on saturated-unsaturated seepage theory，the change of seepage field in slope and its influence on the slope stability under rainfall infiltration are analyzed.The study results show that:①rainfall infiltration is a saturated-unsaturated process，and its internal volumetric water content changes dynamically with the change of rainfall duration，in the initial stage of rainfall，the soil is in unsaturated state，the cohesion increases with the increase of water content，and the variation of internal friction angle is small，its overall trend is downward，with the increase of matrix suction and safety coefficient，which is beneficial to slope stability；②with the continuous rainfall，pore water pressure changes from negative to positive，cohesion and internal friction angle decrease with the increase of water content，matrix suction weakens，and slope stability decreases；③the final process of rainfall infiltration is the rise of internal water level，the increase of dynamic and static water pressure，and the decrease of effective soil weight，the soil softens， the mechanical strength parameters decrease，and the stability of the slope decreases，the permeability coefficient of the soil is inversely proportional to the safety factor of the slope as a whole.Based on the above discussion results，combined with the example of soil slope，the strength reduction method is used to reveal the change rule of the potential slip surface and the peak displacement of the slope along with the rainfall duration time under the condition of rainfall infiltration.The results indicated that the potential sliding surface at the beginning of rainfall increases from shallow to deep，and the peak displacement increases continuously；after the rainfall stopes，the stress in soil is re-distributed，the soil changes from saturated to unsaturated，and the potential sliding surface and peak displacemenet change inversly.In order to prevent the slope from destabilizing and destroying by rainfall，the rationalization treatment suggestions of soil slope are put forward， which provides a reliable reference for the comprehenisve treatment of unsaturated soil slope.