Study on the influence of freezing temperature and gas pressure on coal frost heaving effect

As China's coal mining gradually enters the deep stage, the difficulty of coal and gas outburst prevention and control is increasing. Low-temperature freezing technology has the dual effects of reducing coal seam storage energy and improving coal mass strength and has received widespread attention in the coal mining industry in recent years. When freezing water-bearing coal, frost heave occurs inside the coal mass, which reduces coal mass strength and then affects the application effect of cryogenic outburst prevention technology. In order to investigate the influence mechanism of freezing temperature and gas pressure on the frost heave effect of the coal mass profoundly, the water-bearing gas-containing coal freezing and cooling test was carried out using the self-developed gas-containing coal freezing and cooling test platform. The change rule of the temperature and strain of the coal mass was analyzed during the freezing process. The research results indicate that both freezing temperature and gas pressure impact the frost heave effect of coal. When the freezing temperature is below −10 °C, there is an exponential relationship between the frost heave strain generated by coal and the freezing temperature. When the equilibrium pressure of gas adsorption is less than or equal to 1.5 MPa, there is a linear positive correlation between the frost heave strain generated by coal during the freezing process and the gas pressure. In engineering applications, measures can be taken to reduce the freezing temperature and gas pressure to minimize the amount of coal frost heave strain. However, the freezing temperature should not be lower than −20 °C.