Dynamic distribution and prevention of spontaneous combustion of coal in gob-side entry retaining goaf

The 11101 working face of Qipanjing Mine was taken as the research object to explore the dynamic change law of the spontaneous combustion of the remaining coal in the gob-side entry retaining goaf area. A sealed oxygen consumption experiment was conducted to determine the (critical) oxygen volume fraction in the suffocation zone and continuous oxygen consumption rate of coal samples. The parameters of the working face were measured on site, and the air volume fraction in the goaf was monitored using a beam tube. Considering upward ventilation and the effect of gravity, a UDF control program for the falling medium in the gob-side entry retaining goaf was written. Based on the experimental results, a control program for the continuous oxygen consumption rate of the remnant coal was compiled, the dynamic distribution of the flow field in the gob-side entry retaining goaf was simulated with different advancing positions and air leakage at the working face, and a prediction model for the spontaneous combustion danger area was established. Finally, fire prevention measures via grouting in the return air lane side and nitrogen injection in the retaining lane side were put forward. The results showed that with the variation in the advancing position of the working face or in the air leakage of the air intake lane, the range of the natural hazardous area of the gob-side entry retaining goaf presents a distribution with a power function SF = xn+b (0 < n < 1). The theoretically proposed fire-fighting measures can effectively reduce the risk of spontaneous combustion of coal.