运用分形模型预测非饱和土的土水特征曲线与导水系数曲线,结合孔隙气体流动分析,模拟降雨入渗条件下的一维非饱和渗透过程。根据非饱和土抗剪强度的分形模型,导出降雨入渗下非饱和土边坡临界深度公式,并分析了影响边坡稳定性的因素。非饱和土的分维与进气值影响土体的水理性质。分维影响降雨的入渗速度与入渗深度,而进气值影响降雨入渗下土体吸力的变化曲线形态。非饱和土的饱和导水系数与降雨强度对边坡稳定性影响较大,在降雨强度远大于非饱和土的饱和导水系数时,孔隙气体在降雨入渗过程中将产生气压,对吸力产生影响。

The fractal model in association with pore airflow analysis is employed to forecast the process of one-dimension unsaturated soil seepage under rainfall. First, curves of water-soil characteristic and hydraulic conductivity coefficient of saturated soil with different fractal dimensions and air-entry values were predicted. Furthermore, according to the fractal model for unsaturated shear strength, a new formula of the critical depth for rainfall-induced failure of unsaturated soil slope is derived. Factors controlling the instability of unsaturated soil slope under rainfall are analyzed. Results show that the fractal dimension and air-entry value determine the water-physical property of unsaturated soil. The rate and depth of rainfall infiltration are affected by the fractal dimension, while the soil suction curve is influenced by the air-entry value. The coefficient of saturated hydraulic conductivity and the rainfall intensity has large impact on the instability of unsaturated soil slope. When rainfall intensity exceeds the coefficient of saturated hydraulic conductivity, pore air pressure will be generated subject to infiltration, and hence affecting the soil suction.