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For making full use of seasonal difference of rock and soil strength of open-pit coal mine slope, improving the angle of end-slope during mining in winter and increasing the extraction amount of coal, based on the strength theory of seasonally frozen soil and the direct shear experiment under the action of freeze-thaw, using the Geo-Slope stability analysis software, combined with physical and mechanical parameters of slope strata in winter and summer, on the basis of meeting the stability coefficient of end-slope required by regulations, this paper calculates the maximum safety angle in winter and summer as well as the enhancing range of end-slope stability coefficient in winter. The results show that: with the same angle of slope, Fs increases from summer to winter, and the average enhancing range of stability coefficient at different angles is 7.34%. Seasonal steep mining is able to increase the angle of end-slope from 39° in summer to 41° in winter. Based on steep mining under the seasonal difference of rock and soil strength, increase coal recovery of end-slope by 81 100 t and economic benefit by 6.540 5 million yuan; the safety of the end wall in the transition period can be guaranteed by increasing the amount of earth of the inner pressure displacement wall by 3 600 m3.

In order to make full use of the difference of seasonal freeze-thaw strength of the soil on the free face of the slope to improve the recovery rate of the coal under the end-slope, the mechanism of the improvement of the shear strength of the frozen soil is analyzed by using shear plane microstructure model. Two kinds of strips mining methods for the secondary steep mining in the freezing period are proposed, and the optimal strips width analysis flow is designed. A case study on the south end-slope of Western Shengli No.1 open-pit mine is carried out. The results show that the stability factors of the south end-slope in the non freezing period and freezing period are 1.06 and 1.14, respectively. The second steep mining can be carried out in the freezing period, and the optimal strips width is determined to be 60 m by analysis. The secondary steep mining realized that the south end-slope angle was raised from 30° to 33° and the end-slope residual coal was recovered by 171 500 t. In the seasonal frozen soil area, the implementation of the strips secondary steep mining can ensure the safety of the slope and further improve the recovery rate of resources.