水位下降过程中气相对土坡稳定性的影响

基于饱和-非饱和水-气二相流模型,对土坡在水位下降过程中的孔隙水压力、孔隙气压力、毛细压力及水相饱和度的变化过程进行模拟;基于模拟得到的不同时刻的渗流状态,采用Bishop简化方法推导出考虑孔隙气压力及坡外水压力的土坡安全系数计算公式,分析了水位下降过程中不同渗透性土坡安全系数的变化规律,及基质吸力和气相的存在对边坡稳定性的影响。结果表明:水位下降过程中土坡的安全系数逐渐减小,水位下降后土坡的安全系数略有增大;考虑气相影响后土坡的安全系数降低,考虑基质吸力影响后土坡的安全系数增大;岸坡土体的渗透率越大,水位下降过程中安全系数较大,而水位下降后安全系数较小。

Effects of Pore Air on the Stability of Soil Slope during the Process of Water Level Drawdown

In this study, a water-air two-phase flow model was used to simulate the changes of pore water pressure, pore air pressure, capillary pressure and liquid saturation. The modified Bishop method was used to calculate the slope stability taking into account the pore air pressure and water pressure under water level based on the transient seepage field obtained by the water-air two-phase flow model. The variations of the safety of the factors for the different soil slopes were analyzed during the process of water level drawdown. The influences of matric suction and gas phase during water level drawdown process on the safety factor were discussed. The results show that the safety factor of the slope decreases during the water level drawdown process and then increases after water level drawdown; the safety factor considering gas phase is less than that in the case without considering gas phase; the safety factor considering matric suction is greater than that in the case without considering matric suction; during the water level drawdown process the safety factor is greater and after the water level drawdown the safety factor is smaller with the higher hydraulic conductivity.