大降雨条件下气压力对边坡稳定的影响研究

对于大面积浅层风化土边坡，当下部含有浅水位或不透水基岩层时大降雨将导致下部气体被封闭。随着湿润峰的下移，气压不断增大。封闭气压力不仅降低了雨水在边坡土体的入渗率，而且对边坡的稳定有显著影响。通过分析封闭气压力的形成和相关理论，提出取 大小的气压力头来研究边坡的稳定性（Hc为一水头值，与土体孔隙尺寸分布有关； hd为土体进气值水头）。结合非饱和土的Mohr-Coulomb破坏准则和极限平衡法，将封闭气压力引入到边坡的稳定分析中，建立了考虑气压力影响下的稳定分析模型。与传统的不考虑气压力的稳定分析方法作对比，提出了气压力影响率概念。研究表明，封闭气压力显著降低了边坡的安全系数，传统的无限边坡稳定计算方法偏于危险。研究结果对无限边坡的强降雨安全预报具有较好的指导作用。

Research on effect of closed air pressure on slope stability under intense rainfall

For a large area of shallow slope covered with weathered soils, when the groundwater table or the impermeable bedrock is shallow, intense rainfall will result in the air in soils being closed. With the wetting front moving downward, air pressure increases constantly. Closed air pressure not only reduces rainwater infiltration rate of the soil in slope, but also has a significant effect on slope stability. This paper analyzed the formation of air pressure and its related theories, and suggested that a pressure head was used to study slope stability(Hc is a value of water head related to the pore size distribution; hd is an air-closing water head). Combining the Mohr-Coulomb failure criterion of unsaturated soil and the limit-equilibrium method, the closed air pressure head is applied to slope stability analysis; and the stability analysis model is established considering air pressure. The comparison was also carried out with the classical stability analysis method; and a concept of effect rate of air pressure is also defined. It is found that closed air pressure significantly reduce the safety factor of slope stability; the classical stability analysis method of infinite slope is more dangerous; research results in this study of infinite slope safety prediction have a great guide significance.