Dynamic gas migration and integrated prevention and control in the goaf

The accumulation of gas in goafs can lead to excessive concentrations at the working face, potentially triggering gas explosions and posing a significant threat to mine safety. Understanding the migration characteristics of goaf gas is crucial for effective gas control and hazard prevention. In this study, a time-varying, deformation-driven dynamic mesh model was developed based on the 3207 fully mechanized caving face of Zhongtai Coal Mine in Henan Province. By analyzing the temporal and spatial evolution of porosity in the goaf, the effects of varying face advancement rates and ventilation volumes on gas concentration distribution were systematically investigated. Simulation results reveal that during the initial phase of face advancement, gas concentration in the goaf remains low and within safe thresholds. However, after 40 days of continuous advancement, gas concentration on the return airway side rises sharply, with significant accumulation in deeper goaf regions. Furthermore, increasing the face advancement rate markedly exacerbates gas concentration levels. Optimal operational parameters were determined, with a recommended face advancement rate of 4 m/d and a ventilation volume of 1000 m3/min. A comprehensive goaf gas prevention and control strategy was subsequently proposed and successfully implemented in the field. Monitoring after implementation indicated a substantial reduction in average gas concentration within the goaf, particularly on the return airway side, achieving an average decrease in 63.3%. This effectively mitigated the risk of gas-related accidents and enhanced mine safety.