Study on Regional Evolution Characteristics of Coal Spontaneous Combustion and Gas Coupling Disaster in Composite...

To investigate the evolution of the coupling disaster risk area in composite goaf with no-pillar mining, the fluid-solid coupling model of the coal spontaneous combustion process was constructed and verified based on the physical similarity of the goaf's thermodynamic disaster. The multifield development rule in composite goaf was compared when the nonfirst mining face advances to different positions. The results show that the O₂ entering the goaf from the retained gob-side entry from the previous mining face is continuously reduced, while CH₄ continues to accumulate in the goaf of the previous mining face and diffuses to the newly formed goaf by mining. Under the effects of spontaneous coal combustion, the heat accumulation position is mainly located in the area directly behind the mining face and the vicinity adjacent to the retained gob-side entry on the return-air side. The generated CO continues to accumulate in the center of the goaf formed by the mining face. Dangerous areas of coal spontaneous combustion and gas coupling disasters are mainly concentrated at the return side near the upper corner and at the newly formed goaf close to the mining face, while there are almost no coupled disaster dangerous areas formed in the goaf of the previous mining face. In addition, areas of both the oxidation and gas explosion zones continuously decrease as the mining face advances; in contrast, the area of the coupling disaster area remains almost unchanged, which also offers a certain theoretical basis for preventing and controlling thermodynamic disasters in the composite goaf with no-pillar mining.