Stability Evaluation of Open-Pit Coal Mine Slopes Under Rainfall Infiltration Effects: A Case Study

Landslide disasters in open pit mining cause severe loss in engineering excavation and human safety. The stability evaluation of the open pit mine slope is difficult due to the complex lithology distribution and fluctuation of underground water. In addition to the inherent characteristics of the slope itself, rainfall may exacerbate and weaken its stability. In this work, a case study of the Shengli open-pit coal mine in Inner Mongolia is being considered. The high-precision formation profiles are established according to the data from the drilling hole. Then, a series of slope stability evaluations are conducted, considering the inclined and anti-inclined characteristics, the weak interlayer, and the dynamic rainfall infiltration of local hydrogeological and meteorological conditions. The results show that under natural conditions, all slopes of open-pit mines can meet the stability requirements. With the fluctuation of underground water levels, landslides may occur along the weak interlayer, and therefore, pumping water or controlling underground water levels is key in coal mine excavation. Rainfall infiltration has an impact on slope stability, especially when the top layer is saturated. While considering local rainfall conditions, all slopes meet the stability requirements. Finally, the slope of excavation is evaluated and a recommended safe angle for excavation is quantified. This study’s findings may provide guidance for the safe development and design of open-pit mines.