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Improving slope stability is one of the important ways to ensure the safe operation of open pit coal mines and improve the resource recovery rate. Through Bishop’s analysis, the derivation of the expression of slope stability coefficient of replacement layer was carried out, and the influence of depth and height of replacement layer on slope stability coefficient was analyzed by combining Geo-Slope numerical simulation to verify the derivation. The study shows that: the influence of the replacement depth on the slope stability coefficient is not obvious before the contact between the replacement layer and the slip surface and after the contact part is unchanged, and the slope stability coefficient increases when the replacement depth supports the contact between the replacement layer and the slip surface; the influence of the replacement height on the slope stability coefficient is not obvious before the contact between the replacement layer and the slip surface before the contact between the replacement layer and the slip surface, the effect of the replacement height on the slope stability coefficient is not obvious, and after the contact between the replacement layer and the slip surface exists, the replacement height and the slope stability coefficient are positively related.

Based on discrete-continuous coupling method and taking the end slope after steep mining of thick coal seam open-pit coal mine as research background, the DEM is used to model and analyze the landslide characteristics, damage process and influence range in the potential instability area of the slope; the FDM grid is established for the small deformation part of the slope bedrock to transfer the internal stress of the slope body and improve the calculation speed. The results show that: the location of the slip surface calculated by the discrete-continuous coupled calculation method and the FDM is similar, and it is a circular-shaped landslide. The landslide process starts with a small amount of damage of the bond between the particles on the slope surface by lateral deformation, and the particles roll down and accumulate at the foot of the slope after the bond is broken; then tension cracks appear at the back edge of the slide body, and the slide surface is gradually clear, and the coal seam at the front edge of the slide body is misshapen, which hinders the further development of the slide under the influence of the reverse tilt structure. The rock mass on the lower side of the slope is damaged first, and then the damage area gradually moves up. After the landslide, there are many tensile cracks in the top 580 m level of the slope, and there is obvious subsidence at 61.37 m from the slope shoulder, about 30 m; the rock strata of the slope are obviously staggered, the lower coal steps and roof are pushed to the face of the air, and the horizontal displacement of the lower reaches 42.39 m.

In the process of mining and transportation, the temporary non-hardened mine-road structure is mainly a mixture of soil and stone, which very easily produces dust hazards via crushing and wind transportation. Geopolymers can be used in the road's soil and stone mixture so that the road reaches certain strength requirements in line with the short-term use of the mine. However, in alpine open-pit coal mines, which are subject to the influence of weather changes, freezing and thawing phenomena will affect the long-term use of the road and its normal and safe operation. An open-pit coal mine in Xinjiang, China, was chosen as the research object of alpine open-pit coal mines. Using the method of indoor testing, different freeze–thaw freezing temperatures, different numbers of cycles, changes in the mechanical properties of the mine-road materials, and microscopic changes were studied. From the experimental results, it was determined that with a reduction in the freeze–thaw freezing temperature, the specimen strength declines after stabilizing, and with an increase in the number of freeze–thaw cycles, the specimen strength exhibits a linear decline. The specimen's internal structure gradually changed from dense to loose; the fracture mode changed from toughness fractures to crystal fractures after the removal of the maximum load reduction. The uniaxial compressive strength was reduced to 61%; the tensile strength was reduced to 49%. The fracture zone of the specimen was analyzed using energy spectra, and the main elements changed from O (57.19%), Si (17.07%), and Al (12.19%) without freezing and thawing to O (49.76%), Si (15.70%) and Ca (11.09%) after freezing and thawing. [ABSTRACT FROM AUTHOR]