非饱和非稳定渗流作用下边坡稳定的有限元塑性极限分析下限法

常规的土坡稳定性分析方法主要是基于饱和土理论和稳定渗流情况,难以反映降雨作用和水位骤降对边坡稳定的影响,而实际上相当一部分坡体失稳是由于非饱和非稳定渗流引起的。基于Bishop提出的非饱和土有效应力原理以及Fredlund双应力强度理论,将任意时刻的水压力当做体积力考虑到平衡方程中,用基于有效应力的方式建立满足平衡条件、间断条件、应力边界条件以及屈服条件下考虑非饱和非稳定渗流作用的下限法非线性规划模型,并且编制了相应的程序。通过对降雨入渗和库水骤降的边坡数值算例的分析,验证了所提方法的正确性,对非饱和非稳定渗流作用下土坡失稳的规律有了进一步的认识。

Lower bound analysis of slope stability subjected to transient unsaturated seepage

The conventional methods for slope stability analysis are mainly based on the theory of saturated soils and the stable seepage situation and difficult to reflect the influence of rainfall and water level drawdown on slope stability. Actually quite a number of slope instabilities are caused by transient unsaturated seepage. Based on the effective principle of unsaturated soils by Bishop and the theory of two-stress-state-variable mechanism of the shear strength by Fredlund, the water pressure at any time is introduced into the balance equation as the volume force and the effective stress fields satisfying the conditions of equilibrium, stress boundary, yielding and stress discontinuity are constructed. By using the idea of nonlinear programming, a lower bound analysis model for the slope stability subjected to transient unsaturated seepage is established, and the corresponding program is compiled. Through numerical examples of impoundment drawdown and rainfall infiltration analysis, the correctness of the proposed method is verified, and a further understanding about the law of slope instability subjected to transient unsaturated seepage is obtained.