Numerical simulation study on the three-dimensional mechanical response of high and steep slopes induced by excavation unloading in a large open-pit mine

A limestone hillside open-pit mine has a deep downward mining and stripping depth, and the stope rock slope formed at the end of mining has a height of 195 m, with a final slope angle of 49 º, which belongs to a typical high and steep slope. The stability of this high and steep slope is directly related to the normal operation of the mine. Therefore, in order to study the stability of the high and steep slope of the open-pit mine, the geological data of slope engineering exploration and the test results of rock mechanics are deeply analyzed. Combined with field investigations, stereographic projection and qualitative evaluation analysis of rock mass quality are carried out. At the same time, a three-dimensional numerical calculation model of the open-pit mine slope is established. The FLAC^3D numerical analysis software is used for numerical simulation calculation to reproduce the slope failure evolution process. The numerical simulation results show that the slope at the final boundary of the open-pit mine is in a stable state, and the safety factor meets the requirements of the specification safety level; a certain degree of stress concentration occurs in the slope toe area, and the maximum compressive stress it bears is between 1.5 MPa and 2 MPa; the tensile stress value on the slope is very small and does not exceed the tensile strength value of limestone rock mass, and the slope rock mass will not undergo tensile failure; there is no plastic failure sliding surface penetrating from the slope toe to the slope top in the final slope. The maximum subsidence displacement value of the slope is 4 cm, which is located in the middle area at the top of the slope. The value is very small and has basically no impact on the stability of the slope. Through the above research and demonstration, it shows that the structural parameters of the slope in the mining area have certain rationality and safety, and the overall safety and stability of the slope are guaranteed, which provides guidance basis for the safe mining of the open-pit mine in the future.