Study on the Influence Mechanism of Air Leakage on Gas Extraction Effect—A Numerical Case Study of the Coal Mine Site in Anhui

Abstract

Air leakage in mine gas drainage drilling is a critical factor that affects gas extraction efficiency. It leads to a rapid decline in gas concentration, resulting in lower extraction efficiency and potential secondary disasters. To address this issue, a fully coupled gas–air mixed flow model is established in this study. The model examines the effects of extraction time, different negative pressures, and gas leakage on gas concentration. Additionally, it reveals the mechanism of air leakage around gas drainage boreholes. The simulation data are then compared with field gas drainage monitoring data to verify the reliability of the model. This verification serves as a basis for extraction regulation and control. The results demonstrate that during the later stages of extraction, the negative pressure decreases, causing a decline in gas concentration. Moreover, higher negative pressure leads to increased air inflow into the borehole, thereby reducing gas concentration. Consequently, selecting an appropriate negative pressure is crucial to improve pumping efficiency. The research findings hold significant guidance in achieving efficient gas mining.