Grouting modification control technology for broken roof in the retreat channel of the large mining height working face

To control the stability of the broken roof in the retreat channel with large section under strong mining, taking the retreat channel of the 112203 working face of Xiaobaodang No.1 Coal Mine as the project background, we comprehensively adopted the methods of on-site research, numerical calculations and industrial experiments, and analyzed the influences of the initial permeability coefficient, the grouting pressure, and the grouting time on the radius of the grouting slurry dispersion. The key parameters of grouting modification for the retreat channel of 112203 working face was determined: the grouting material is silicate-modified polyurethane material for coal mine reinforced coal rock body, the grouting pressure is 15 MPa, the grouting time is 20-30 minutes. The technical scheme of grouting modification for three parts, including the end of the working face, the air-return roadway, and the main retreat channel, has been proposed. On-site monitoring results show that the integrity of the roof in each part is better after the grouting modification without roof caving, and the roof sink of the 112203 main retreat channel has been effectively controlled.