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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Hc=1.105hd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MohrCoulomb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。
For large shallow weathered slopes, heavy rainfall will cause the lower gas to be trapped when the lower part contains shallow water or impervious bedrock. With the wetting peak down, the pressure is increasing. Closed gas pressure not only reduces the infiltration rate of rainwater in slope soil, but also has a significant impact on slope stability. By analyzing the formation of closed gas pressure and related theories, we propose to study the stability of the slope by taking the pressure head of Hc = 1.105 hd (Hc is a head value, which is related to the pore size distribution of the soil; hd is the soil intake Value head). Combined with MohrCoulomb failure criterion and limit equilibrium method for unsaturated soils, the closed gas pressure is introduced into the stability analysis of the slope, and a stable analytical model considering the influence of gas pressure is established. Compared with the traditional method of stability analysis, which does not consider the pressure of gas, the concept of the influence rate of gas pressure is proposed. The results show that the closed gas pressure significantly reduces the safety factor of the slope, and the traditional method of calculating the infinite slope stability is more dangerous. The research results have a good guidance on the prediction of heavy rainfall safety in infinite slope.