非饱和-非稳定渗流条件下的边坡临界滑动场

Critical slip field of slope under the condition of transient unsaturated seepage

受季节性降雨或水库运行的影响,岸坡外水位及坡内孔隙水压力场的变化较大,不利于岸坡的稳定性。在水位变化过程中,利用非饱和-非稳定渗流有限元计算得到孔隙水压力场,基于非饱和土的渗流和抗剪强度理论,对水位变化过程中的边坡临界滑动场法进行改进,提出可考虑水位变化与岸坡非饱和-非稳定渗流过程的边坡临界滑动场数值模拟方法。将改进后的水位变化过程中的边坡临界滑动场法分别应用于黏土、粉土岸坡在水位升降过程中的稳定性分析,研究了水位升降速率及基质吸力对岸坡稳定性的影响,并揭示了边坡在水位变化过程中的稳定性变化历程。研究表明,该方法计算结果合理、可靠,更适用于涉水边坡的稳定性计算,且岸坡稳定性变化历程受水位升降速率、基质吸力等多种因素共同影响,只有在考虑非稳定渗流的基础上同时考虑基质吸力的作用才能正确得出水位变化过程中岸坡稳定性变化规律和实质。

Seasonal rainfall and reservoir operation can cause the fluctuation of reservoir water level and the change of pore water pressure distribution in the slope body, which is detrimental to slope stability. Based on the theory of shear strength of unsaturated soils and pore water pressure field obtained with finite element method for the transient unsaturated seepage, an improved numerical procedure for critical slip field of slope is proposed. In this procedure, the combined effect of water level fluctuation and transient unsaturated seepage on the behaviors of slopes can be taken into account. First, the transient unsaturated seepage fields of a clay/silt slope are calculated using SEEP/W module in Geostudio to obtain pore-water pressure fields, which are imported into the improved procedure of critical slip field of slope method to evaluate changes in the factor of safety with changing water level. In addition, the influence of fluctuation velocity of water level and matric suction on the slope stability are also analyzed emphatically; and the slope stability changing course with water level fluctuation is revealed, so as to show the feasibility and reliability of the improved procedure. Moreover, the results not only show that the slope stability changing course is affected by fluctuation velocity of water level, matric suction, and so on, but also reveal that the more reasonable slope stability changing rules and essences are obtained by considering matric suction.