UNSATURATED INFILTRATION PROCESS AND STABILITY CALCULATION METHOD OF OVERBURDEN SLOPE CONSIDERING INITIAL WATER CONTENT DISTRIBUTION

A laboratory rainfall test model is designed according to the characteristics of the overburden slope. The test results shows that the initial water content distribution is inversely proportional along the elevation. It is futher assumed that rainfall infiltration is controlled by the total rainfall when the slope surface is unsaturated. An analytical calculation method for rainfall infiltration in the overburden slope under undrained condition is then established. A slope stability calculation method for unsaturated overburden slope is also established considering the rainfall infiltration theory and the shear strength variation of unsaturated soils. The influence of overburden thickness,initial water content distribution parameters and slope angle on slope stability are analyzed. Research results are as follows:(1)The initial water content distribution in the overburden slope is approximated with an inverse proportional distribution. Based on the total rainfall control assumption,an analytical calculation method is obtained for the rainfall infiltration of the overburden slope considering the initial water content distribution. (2)With the assumption of a semi-infinite space volume,a method is given for calculating the factor of safety of the sliding surface at different positions of the overburden slope under rainfall infiltration. (3)The initial stability of the slope decreases with the increase of the thickness of the overburden soil under the same rainfall conditions. The influence of rainfall infiltration on the stability of overburden slope decreases with the increase of overburden thickness. (4)The stability of the slope decreases with the increase of the initial water content distribution parameter of the overburden soil when the rainfall is the same. The longer the rainfall time,the more obvious the influence of initial water content distribution on slope stability. (5)The stability of the overburden slope at different angles gradually decreases with the increase of rainfall. In the initial state,the minimum stability coefficient caused by the increase of the slope angle decreases the most. As the rainfall increases,the slope stability is gradually reduced by the angle.