Study of Seepage Laws of Deep Rock Mass Under Different Water Temperatures Based on Porous Media

Deep coal mining is faced with high temperature, high seepage pressure, and high ground stress, and there is a complex nonlinear coupling relationship between the temperature of water in deep rock mass and its seepage. Based on the background of deep mining in Zhaolou Coal Mine in Shandong Province, China, the hydraulic conductivity of artificial rock samples with similar materials was tested indoors under different water temperatures of 30~80 °C. On the basis of deep rock samples collected in the field, the hydraulic conductivity has a nonlinear positive correlation with the rise of water temperature. The difference in hydraulic conductivity at the highest and lowest temperatures is two to three times. By means of multi-physics coupling finite element software (COMSOL Multiphysics, COMSOL Inc., Stockholm, Sweden), combined with the actual geological background, the regularity was found to be consistent with the laboratory experiment and further proves that the inlet pressure has no effect on the hydraulic conductivity. Subsequent analyses revealed that the influence of temperature on the seepage field is mainly reflected in the change of fluid kinematic viscosity with temperature, which causes the change in the hydraulic conductivity. According to the formula, the hydraulic conductivity of the rock at 80 °C is 2.31 times higher than its hydraulic conductivity at 30 °C, which is matched by the indoor test results. The engineering performance is that as the temperature of the deep rock body increases, the ability of water to penetrate rocks increases, and the water inflow of the working face increases. The results can be applied to the prevention of water hazard threats in deep coal mining.