降雨条件下多层土坡入渗机理与稳定性分析

Infiltration Mechanism and Stability Analysis of Multilayer Soil Slope Under Rainfall Conditions

基于VG(Van Genuchten)模型多层土含水率方程,建立了考虑边坡倾角的含水率与基质吸力控制方程,提出了土层间渗透系数比不同的情况下多层土坡入渗深度计算方法.通过在Geo-Studio软件中的Seep/w板块建立多层土的一维和二维模型,分析雨水入渗过程中土层交界面处饱和滞水区形成过程及不同降雨条件下多层土坡稳定性变化规律,并验证本文计算方法的正确性.结果表明:多层土坡降雨过程中,土层交界面处体积含水率、孔隙水压力变化范围较大,对于各层渗透性不同的多层土坡,在同一降雨强度下,渗透系数比越大,则交界面处滞水向下消散的速率折减得越多,交界面处孔隙水压力变化范围越大;多层土坡在交界面处出现饱和滞水区后孔隙水压力急增,导致土抗剪强度骤降,进而引发土坡稳定性系数大范围下滑.上述结论为降雨边坡预警工作提供参考依据.

Based on the multilayer soil water content equation of VG(Van-Genuchten)model,the governing equation of water content and matrix suction is established,with the slope inclination angle taken into account,and the calculation method of infiltration depth of multilayer soil slope with different permeability coefficient ratios between layers is proposed.One-dimensional and two-dimensional models of multilayer soil are established by Seep/w plate in Geo-Studio software to analyze the formation of saturated stagnant water zone at soil interface during rainfall infiltration and the variation characteristics of multilayer soil slope stability under different rainfall conditions.The correctness of the calculation method is verified.The results show that the volume water content and pore water pressure at the interface of multilayer soil slope change greatly during rainfall.For multilayer soil slope with different permeability of each layer,the larger the ratio of permeability coefficients is,the more the rate of downward dissipation of stagnant water at the interface decreases,the larger the range of pore water pressure at the interface is.The pore water pressure increases sharply after the saturated stagnant water area forms,which leads to the sudden decrease of shear strength of soil and the large-scale reduction of stability coefficient of soil slope.The conclusions provide a reference for the early warning of soil slope under rainfall conditions.