Dynamic evolution of rock mechanical properties of coal seam roofs under thermal loading: A case study of the Baikouquan area, Xinjiang, China

ObjectiveUnderground coal gasification (UCG) represents a key technology for the clean utilization of coal resources. However, during the UCG process, thermal damage to surrounding rocks under thermal effects directly affects the stability and engineering safety of gasification channels.MethodsTo address the thermal damage to surrounding rocks during UCG, this study investigated the silty mudstones and coarse-grained sandstones in the coal seam roof of the Xishanyao Formation, Baikouquan area, Xinjiang. Through high-temperature uniaxial compression experiments, combined with characterization methods like X-ray diffraction (XRD) and scanning electron microscopy (SEM), this study delved into the dynamic evolutionary patterns of rock mechanical properties and the macro-micro damage differentiation of both rock types under thermal effects. Moreover, this study quantified the critical threshold of thermal damage and analyzed the synergistic damage-inducing mechanisms.Results and Conclusions In terms of rock mechanical properties, the silty mudstones experienced thermal strengthening (25 ℃ to 600 ℃ to ≤800 ℃) stages, with peak stresses showing an increase of 36.24%, a decrease of 45.99%, and a surge of 75.20%, respectively. In contrast, the coarse-grained sandstones experienced the dehydration weakening (25 ℃ to