Cohesion and friction angles are the main parameters determining rock strength and deformation. In open-pit mines, the shear strength parameters cohesive forces and friction angles of rock will decay with the excavation of mining and the time existence of slopes, and eventually reached to a stable value- long-term strength. The slopes of Shuichang iron open-pit mine were selected to analyze the stabilities and reinforcement by using three-Dimensional Distinct Element method. Results showed that the horizontal displacements at the upper of the slope increased dramatically when long-term strength parameters were considered than not, and the slope was instable. The slope will be stable with the reinforcement of anchor cables. Therefore, long-term strength parameters must be considered when analyze the stability of slopes in order to ensure the accuracy of the slope stability evaluation.
Slope stability analysis in open pit mines is always a long-term task accompanied with mining. As the development of mining, rock mass is unloaded and the mechanics parameters of rock mass changed with time. Thus, the characteristic of time-development of rock mass must be considered when the stability of the slope is analyzed and reinforcement is designed to provide a reasonable solution for reinforcement in open pit mines.
Shuichang iron open-pit mine of the Capital Iron Company is located in Qian'an City, Hebei Province, it is the main raw material base of the company. The lithologies of the slope are mainly composed of quaternary artificial deposits, breccia, magnetite, gneiss etc. A large number of engineering practices show that the strength parameters are time-dependent. The reason of strength reduction is the destruction of rock mass, the chemical and physical reaction and the change of environment.
The slope in zone II of Shuichang mine was selected as a case. Considering the long-term strength of rock mass, three-dimensional discrete element software was used to evaluate slopes deform at before and after reinforcement.