Research on Spontaneous-Combustion Prevention and Control Technology in Gob-Side Entry Retaining Goaf

Severe air leakage in the goaf of gob-side entry retaining panels can intensify oxygen supply to residual coal and consequently increase the probability of coal spontaneous combustion. Taking the 3451S working face of a coal mine in Hebei Province as the engineering case, this study integrated in situ beam-tube monitoring with Fluent-based numerical simulation to characterize the evolution of the spontaneous-combustion three zones and to optimize prevention and control measures. The results demonstrate that the oxidation zone is characterized by an inclined, continuous band-like distribution penetrating the goaf. The simulated oxygen distribution is consistent with the field measurements, demonstrating the reliability of the established numerical model. The ventilation pattern markedly affects the air-leakage flow field and oxygen concentration distribution, and the Y-type ventilation mode exhibits a higher spontaneous-combustion risk. When the air-volume ratio between the 3451S haulage roadway and the gob-side retained entry is adjusted to 3:1, the oxidation-zone area decreases by approximately 11%. A combined control strategy involving cement-blanket and polymer-spraying leakage sealing, together with precise nitrogen injection, is then proposed to improve the goaf oxygen environment. At a nitrogen-injection rate of 600 m3/h, the oxidation-zone area is reduced by 11,160 m2 and the CO concentration remains stable at approximately 4.9 ppm, providing field evidence for improved fire-prevention performance. These results support the design of targeted spontaneous-combustion control strategies for gob-side entry retaining goafs.