In this paper, mainly, we discuss the influence of rain/evaporation for slopes. The evaporation has obviously influence active for the seepage and the mechanical behaviors of unsaturated soil. Some seepage analysis in rain/evaporation and in only rain conditions has been performed for typical slope model. Analysis results showed that the evaporation would cause the suction value increase in the surface party of soil-structure. The volume contraction of unsaturated soil caused by suction increase will induce the tension crack in soil surface far. The modified parameter Sf is presented to modify permeability coefficient of surface soil layer. An equation was suggested to calculate the depth Zn of tension crack zone. Finally, we discuss the variation of safety of stability of slope with depth of tension crack zone and modify parameter Sf increase. The analysis results showed that if there be tension crack zone in the surface layer of slope, the slope stability will obviously decrease with rain infiltration increase in the surface of slope. It is suggested to consider the influence of rain/evaporation process for the stability analysis of slope under some conditions.
It is very important to research the stability state of a slope due to rain. To increasing calculation accuracy for this problem, all influence factors for slope stability in rain process should be discussed. As known, slope failure has a close connection with water seepage in most natural and human cut slopes. The evaporation as like rain is also one main influence factor for the seepage states of slope. If there are some tension cracks that are caused by the volume contraction with water decrease in surface layer of slope, the infiltration behavior of slope would be changed and would increase the failure possibility of slope during rain.