Study on Gas Exchange Characteristics and Determination Method of Air Leakage in Goaf

Air leakage between goaf and working face increases the risk of spontaneous combustion in goaf, posing a threat to production safety in the working face. The study uses CFD software to simulate the impact of wind speed and goaf depth on the distribution of air leakage, oxygen concentration, and carbon monoxide concentration. It was found that as wind speed increases, the air leakage plume and CO gas concentration move towards the return air side, and the air leakage speed at the working face boundary and tases with depth, and the range of CO distribution and the range of oxygen distribution on the intake side decrease. Based on this, a dynamic measurement method for air leakage is proposed. The error of wind resistance value comparison is within ±5%, indicating the feasibility of dynamic quantitative measurement of the air leakage flow field at the working face, which can improve the accuracy of air leakage measurement in the working face. Then the method was applied in the 509 working face of Ma Di Liang coal mine. The results show that the average air leakage volume in the goaf of the 509 working face is 152.19 m3/min, and the average air leakage velocity is 0.41 m/s.