Effect of water on the rock strength and creep behavior of green mudstone

The weakening of rock mass after immersion substantially affects slope stability. Considering the mudstone in the north slope of the Fushun West Open pit as the research object, we investigated the failure and creep characteristics of mudstone under different immersion times and confining pressures. For this, we used a self-developed experimental apparatus that applies biaxial compression loading in a water immersion environment. Water significantly changed the strength and failure mode of the mudstone. The increase in confining pressure limits the expansion of the crack aperture, reduces the rock strength-weakening coefficient, and delays the rock weakening time. The change in cohesion is primarily responsible for the weakening of shear strength during immersion. Based on the creep test results, the creep curve of the soaking specimen was identical to that of the dry specimen in the initial phase. The weakening effect of water on the specimen increased as the soaking duration increased, due to which the creep curve of the soaking specimen gradually approached that of the saturated specimen. Water entered the microcracks and reacted with the rock interior, accelerating rock failure. Consequently, the soaking specimen had the lowest stress level for creep failure and the shortest failure time. The results of this experiment provide a reference for the long-term stability of the flooded slope.