Abstract: Rainstorm could induce a mass of landslides occurrence. There was a different critical rainfall value in different regions, while the rainfall intension was larger than the value, a lot of landslide would occur, thus had been proved by many happened facts. In general, the theory of rainfall infiltration was the recharge rate was a constant when the rainfall intension was larger than the certain critical value, the more redundant rainfalls become the flow on the earth surface, it couldn’t infiltrate into the earth, as was not consonant with the fact that the more precipitation could induce the more landslide. There were a lot of fissures in the slope which had enormously contributed to the rainfall infiltration. It was simulated by finite element method that changes of transient seepage field in the slope with fissures and without fissure, and the slope stability was calculated in different depths potential slip surface via the Bishop method. It was shown that the calculation result, considering the fissures, was more consistent with the macroscopically observed facts. The fissures existing in the slope should be considered enough when the slope stability about rainfall infiltration was evaluated. Only the rainfall intensity was larger than the certain critical value, the enough rainfallfall could infiltrate into slope body along the fissures, the effect of fissures on stability would be obvious.

Key words: landslide, fissure, unsaturated flow, rainfall infiltration, critical rainfall, stability analysis