Experimental Study of the Freeze–Thaw Damage of Alpine Surface Coal Mine Roads Based on Geopolymer Materials

Abstract

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.