Study on the evolution law of the gas flow field based on the distribution characteristics of voids in the overlying strata in a goaf

To study the distribution law and flow field of gas concentration in goafs, using the goaf of the 714 working face in the Qinan Coal Mine as the engineering background, the gas concentration and flow field under different wind speeds were simulated based on the optimized porosity distribution model of gob caving rock using FLUENT software. The results show that, due to the influence of air leakage, the gas concentration in the shallow part of the goaf is greatly affected by the wind speed of the air intake air roadways, while the deep part of the goaf is nearly unaffected by the wind speed. When the wind speed of the intake air roadways is 1 m/s, there are three gas accumulation areas within the goaf, and, when the wind speed is between 2 and 3 m/s, there are only two gas accumulation areas. The distribution law of the gas concentration in the simulation results, based on the location of the gas accumulation areas and the rock properties of the “vertical three zones” in the goaf, informed the design of high-level drilling construction technology for the 714 working face of Qinan Coal Mine, and promising results are achieved.