Research on the Critical Moisture Content of Frost Heaving in Gas-Containing Coal

As the depth of coal seam mining increases, coal and gas outburst prevention and control face unprecedented challenges. In recent years, freezing outburst prevention technology has received attention and been applied in industry; this method mainly improves the strength of the coal body while reducing its energy storage. Research has shown that due to the influence of moisture content, frost heaving occurs in coal bodies during the cooling process, weakening the coal bodies' strength. Therefore, it is necessary to explore the effect of the moisture content on the coal body frost heave. This paper uses a research method that combines laboratory experiments, theoretical analysis, and numerical simulation to study the critical moisture content of frost heaving in gas-containing coal. The results showed that the coal sample can be divided into three stages during the cooling process: the cold shrinkage stage, frost heave stage, and stabilization stage. When the moisture content is greater than 7%, as the moisture content increases, the amount of ice increases accordingly, which causes an increase in the frost heave deformation of the coal sample and produces an obvious frost heave effect. Utilizing COMSOL simulation software, the deformation of gas-containing coal samples at different moisture levels is simulated. By combining the results with laboratory measurements, the critical moisture content for the frost heave in gas-containing coal is determined to be 6.6%.