Abstract: Soft rock slope engineering catastrophic mechanism is a hot difficult subject in slope engineering. According to soft rock slopes unsaturated seepage-stress calculation principles, indirect coupling method is used to analyze soft rock slope stability under rainfall infiltration. A method for analyzing seepage effect has been established. The water-softening characteristics of the shear strength of soft rock are given to the corresponding soft rock in transient saturated zone dynamically, simulating the softening effect of soft rock slope in rainfall seepage. Then, combining seepage and softening, a numerical analysis method for soft rock slope rainfall-seepage-softening-cataclysm analysis has been established based on transient saturation region, which is used to research the disaster mechanism of the slope engineering. The results show that, the depth of the potential sliding surface shallow gradually over time; the shape of stability factor-time curve is reverse recovery curve; and the inflection point appears on the curve when the slope begins to soften. The slope stability calculation results are consistent with the actual situation, so as to show that the proposed thought and method have some validity and can provide a theoretical basis for soft rock slope management program design.

Key words: soft rock slope, rainfall, transient saturated zone, seepage, softening