Assessment of Mechanical Properties for High-Temperature Sandstone in Coal Fire Area Based on Different Cooling Methods

The rocks in coal fire areas are often in high-temperature environments. The mechanical properties of rocks play an important role in mining and engineering disturbance, so we aim to study the static and dynamic properties of high-temperature sandstone in the coal fire zone under different cooling methods, and to evaluate the degree of thermal damage at different high temperatures. The mechanical properties and failure modes of two cooling methods (natural cooling and watering cooling) were analyzed. In addition, the influence of the longitudinal wave velocity (V-p) on the mechanical properties of the high-temperature sandstone was analyzed, and the composition of the high-temperature sandstone was tested by XRD method. Under two cooling conditions, the static and dynamic peak strength of sandstone increases continuously with the increase of longitudinal wave velocity (V-p), and reduces with the increase of heat-treated temperature, but the damage degree increases with the increase of the heat treatment temperature. In the Split Hopkinson Pressure Bar (SHPB) test, the dynamic compressive strength of naturally cooled sandstone is higher than that of water-cooled sandstone. The failure of natural cooling high-temperature sandstone mainly occurs "X-shape", transverse splitting failure or breaks into pieces, but the watering cooling high-temperature sandstone presents transverse or longitudinal splitting failure.