Flexible gas-sealing optimization and leakage prevention mechanism in gob-side entry retaining: An innovative gas control method

In Y-type ventilation systems, sealing walls are prone to crack development under mining pressure, allowing gas to migrate from the goaf into the gob-side entry retaining, creating serious gas accidents. This study proposes a novel flexible gas-sealing technology for gob-side entry retaining applications. Based on this, the interactive effects of three factors—air distribution ratio, airbag width, and airbag thickness—on gas concentration in the gob-side entry retaining were analyzed using a combination of design of experiments, response surface methodology, and computational fluid dynamics (CFD) simulation. The technique parameters were then optimized, and the mechanism by which the flexible airbag influences gas leakage has been elucidated. Finally, the effectiveness of the proposed method was validated through a field test. The results showed that airbag width and thickness had a more significant impact on the gas concentration compared with the air distribution ratio, and strong nonlinear interactions were observed among the three factors. The optimal parameters derived from the response surface optimization were an air distribution ratio of 5:1, an airbag width of 3.414 m, and a thickness of 0.587 m. The airbag alleviated the pressure gradient in the goaf, reduced leakage from the coal face, and increased wind pressure in the gob-side entry retaining, thereby weakening methane leakage intensity. Field tests demonstrated good performance, reducing gas concentration to 0.1%–0.15%, increasing airflow velocity to 2.46, m/s, and decreasing the resistance per 100 m and friction resistance coefficient to 0.009 and 0.012 N·s2/m4, respectively.