Assessing the stability characteristics of high rock slope under rainfall via theoretical research, numerical simulation, and field monitoring is of great implications for safety construction in open-pit mine engineering. Thus, based on the Hoke-Brown criterion, instantaneous internal friction angle and cohesion of high-slope rock mass under high stress conditions were deduced, and a nonlinear strength reduction method for high rock slope was established. The safety factors of the open-pit mine were calculated by COMSOL Multiphysics, which considering the high rock southwest slope and detected rainfall in Dagushan Open-pit Mine, China. The results showed that high rock slope stability could be more accurately analyzed by the proposed method due to its full consideration of slope stress state effect compared with the equivalent Mohr- Coulomb method. When the slope is low, the difference between the calculation results of the equivalent Mohr- Coulomb method and the proposed method is small, but with the increase of the slope height, the difference between the two calculation results gradually increases. When the transient saturated is formed in the slope surface layer and gradually increases, the reduction rate of the factor of safety (FOS) gradually increases. When the total rainfall is the same, the effect of short-term heavy rainfall on slope stability is less than that of long-term ordinary rainfall. The results obtained form this work provided important insights into the stability of high rock slope and rainfall infiltration in open-pit mine, and the safety factor is crucial for guiding the mining process design.
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