Comparison of pseudo-static, Newmark and dynamic response analysis of the final pit wall of Sungun copper mine

Sungun Copper Mine is located in an area with a high level of seismic hazard. Most recently, the Ahar-Varzeqan earthquake with a magnitude of 6.2 on Richter scale occurred on August 11, 2012; at a distance about 40 kilometers away from the mine. Nevertheless, the seismic stability of the final pit wall has not been comprehensively reviewed. In this research, the southwestern wall of the final pit of Sungun Mine investigated by pseudo-static, Newmark and numerical methods. Besides, through the paper, it is tried to explain some of the difficulties in accomplishing and interpretation of results in a dynamic analysis of a mining slope. Pseudo-static analysis revealed that the final pit wall is unsafe against the design earthquake with a high probability of failure. Results of Newmark analysis proved that in the case of design earthquake a large failing region would form. Based on a dynamic numerical analysis of the pit wall, continuous earthquake-induced movements in the forward and downward directions observed, which might be a sign of pit wall instability. The effect of underground water drainage on pit wall stability was investigated in the numerical model. Resulted time histories of the drained pit wall displacements proved that merely water drainage is sufficient for protecting the pit wall against the design earthquake.