Simulation Study on the Spontaneous Combustion Patterns and Prevention Technologies of Residual Coal in Goaf with Retained Roadway

To address the severe issue of spontaneous combustion in residual coal within gob areas under gob-side entry retaining conditions, this study investigates fire prevention strategies during coal mining operations at the 22523 working face of Halaigou Coal Mine through integrated field measurements, experimental analyses, and numerical simulations. The findings reveal that the spontaneous combustion risk zones in gob-side entry retaining faces can be categorized into two distinct regions: the rear section of the working face and the gob-side entry area. The hazard distribution behind the working face demonstrates similarity to conventional “U”-type ventilation patterns, while the combustion risk in the entry-retained side primarily arises from the combined effects of leakage through flexible formwork walls, residual coal distribution patterns, and inherent coal oxidation characteristics. Progressive analysis demonstrates that the maximum oxidation zone and peak temperature locus migrate from the return air side toward the gob-side entry area with advancing face progression. Comparative evaluation of nitrogen injection strategies (single-point, uniform multi-point, and self-regulating multi-point configurations) demonstrates that the self-regulating nitrogen injection system achieves superior fire suppression efficacy compared to single-point injection while reducing nitrogen consumption by 43.3% relative to uniform multi-point injection. These empirical findings establish the technical and economic viability of the self-regulating injection protocol for practical implementation at the 22523 working face.