Fracture Distribution Characteristics in Goaf and Prevention and Control of Spontaneous Combustion of Remained Coal under the Influence of Gob-Side Entry Retaining Roadway

Based on the ventilation characteristics of the gob-side entry retaining face, a mathematical model of spontaneous combustion in the gob-side entry retaining face is established. From the overburden caving of the goaf along the goaf retaining roadway, the development characteristics of rock strata and residual coal fissures in the goaf are summarized and analyzed. In addition, by using numerical simulation software, the effects of normal mining period, goaf retaining roadway as return air roadway, air leakage prevention, and nitrogen injection measures in goaf on spontaneous combustion in goaf are studied, and the distribution characteristics of flow field, oxygen concentration field and temperature field in goaf are obtained. The results show that the mining of the Geng 20 working face has a significant impact on the Geng 19 coal seam. The Geng 19 coal seam is in the range of fracture zone, and the fracture is well developed. Furthermore, the permeability coefficient of the Geng 19 coal seam increases sharply, air leakage in the goaf is increased along the goaf retaining roadway, and the range of oxygen concentration is enlarged, which results in a temperature rise in the goaf. Therefore, air leakage measures are proposed along the goaf to inject 900 m³/h of nitrogen into the goaf, which can prevent the spontaneous combustion of coal left over in the goaf. In addition, according to the characteristics of fracture development and numerical simulation of spontaneous combustion in goaf under the goaf retaining roadway, the hierarchical prevention, control, and fire extinguishing technology system of the goaf retaining roadway is constructed.