“暂态”饱和-非饱和边坡稳定性分析方法研究

针对"暂态"饱和-非饱和边坡的稳定性问题，推导考虑"暂态"水压力、孔隙水重力、软化与非饱和强度的边坡安全系数计算公式，开发可以自动搜索滑动面位置的"暂态"饱和-非饱和边坡稳定性分析程序，并采用该程序研究算例"暂态"饱和-非饱和边坡安全系数与失稳模式的演化规律，分析不同因素对边坡安全系数的影响程度。研究结果表明：提出的能同时考虑"暂态"水压力、孔隙水重力、软化与非饱和强度的改进瑞典圆弧法，可以有效解决"暂态"饱和-非饱和边坡稳定性分析的问题；边坡失稳模式由深层整体破坏转变为浅层局部破坏时，存在一个可以采用降雨入渗区深度定义的阈值；降雨入渗区深度小于该阈值时，边坡安全系数迅速降低，滑动面最大深度快速减小，边坡失稳模式表现为深层整体破坏；降雨入渗区深度大于该阈值时，边坡安全系数持续降低，滑动面最大深度缓慢增大，在边坡浅层形成一块滑动带，边坡失稳模式表现为浅层局部破坏；"暂态"水压力对边坡稳定性的影响有利有弊，孔隙水重力、软化对边坡稳定性不利，非饱和强度对边坡稳定性有利；不考虑"暂态"水压力的抗滑力矩与下滑力矩之比小于滑动面"暂态"水压力及滑体侧向"暂态"水压力引起的抗滑力矩与滑体侧向"暂态"水压力引起的下滑力矩之比时，"暂态"水压力对边坡稳定性有利，反之则不利。

Stability Analysis Method of “Transient” Saturated-unsaturated Slope

In order to achieve stability of "transient" saturated-unsaturated slopes, a calculation formula was derived for the slope stability coefficient, considering "transient" water pressure, pore water gravity, softening, and unsaturated strength. The "transient" saturation-unsaturated slope stability analysis program, which can automatically locate the position of the sliding surface, is developed. The evolution law of the safety coefficient and instability mode of the "transient" saturated-unsaturated slope is studied by this program. The degree of influence of different factors on the safety factor of the slope is analyzed. The results illustrate that the problem of "transient" saturated-unsaturated slope stability can be effectively solved by the improved Swedish arc method, which can simultaneously consider "transient" water pressure, pore water gravity, softening, and unsaturated strength. When the slope instability mode is changed from deep overall failure to shallow local failure, there is a threshold, which is defined by the depth of the rainfall infiltration zone. When the depth of the rainfall infiltration zone is less than the threshold, the safety factor of the slope decreases rapidly, the maximum depth of the sliding surface decreases rapidly, and the instability mode of the slope appears as deep overall damage. When the depth of the rainfall infiltration zone is greater than the threshold, the safety factor of the slope continues to decrease, the maximum depth of the sliding surface slowly increases, and a sliding zone is formed in the shallow layer of the slope. The instability mode of the slope is characterized by shallow local failure. When the ratio of anti-slip torque to slip torque without considering "transient" water pressure less than the ratio of sliding surface "transient" water pressure and sliding resistance caused by lateral hydraulic water pressure to sliding moment caused by lateral "transient" water pressure of the sliding body, the "transient" water pressure is good for stability, and vice versa. Although the gravity of pore water and softening of soil are detrimental for slope stability, the unsaturated strength impacts it favorably.