Slope Stability Analysis For Steep End-wall Mining Of Ha’erwusu Surface Coal Mine

Taking end-wall slope of Ha’erwusu surface coal mine as a case study, several techniques and theories of surface mining principles, slope stability analysis menthod, and numerical simulation were adopted to determine typical cross-section of end-wall slope stability situation with numerical simulation and rock mechanics parameters. Angles of differenet end-wall slope were optimized and haulage system associated with it was also studied.By analyzing constitutive characteristics of end-wall slopes, deformation and failure mechanism were analyzed. Finite Element Method(FEM) with shear strength reduction and three other types of limit equilibrium methods namely Bishop, Janbu, Spencer were adopted to analyze the selected typical cross-sections combined with mining parameters and characteristics of Ha’erwusu surface coal mine. The FEM reflects to stability situation of different cross-sections better than the other three methods, with the analysis results of 1.38 and 1.36 for south end-slope SI-SI and SII-SII, 1.14 and 1.20 for north end-slope NI-NI and NII-NII. Single Factor Sensitivity Analysis Method was adopted to determine the degree of influence of the different factors on slope stability. The analysis result indicates that internal friction angle of 6th coal, 2nd coarse sandstone and 1st coarse sandstone, bench width at 995 mining level and density of 1st coarse sandstone are the key factors. After the optimizing on south and north end-wall slopes of Ha’erwusu surface coal mine, optimal slope angles of 41° and 39° for south and north end-wall were determined on the basis of the minimum stability factor of 1.2 for the south bedding slope and 1.1 for the north inverse slope, which can increase coal production by 320 and 345 thousand tons respectively. Establishing transportation system in middle mining stope with overburden material, serving as inner-dumping haulage, was determined as the optimal transportation system of Ha’erwusu surface coal mine after the end-wall slope was optimized.