Study on floor failure mechanism of paste backfill mining and division area control technology

Aiming at the problem of the safety mining problems of longwall paste filling working face under buildings on high confined water in Daizhuang Coal Mine, through theoretical analysis, numerical simulation and field measurement, the equivalent roadway floor failure theory of paste filling mining face is proposed, based on this theory, the spatial-temporal effect of floor failure in paste filling mining face was analyzed, and the plastic failure zone and its range were obtained. Based on the field practice of 11607 test working face in Daizhuang Coal Mine and the results of FLAC3D numerical simulation, the following conclusions are obtained: when the filling interval of the test working face increases from 1.2 m to 3.6 m, there is no obvious change in the plastic zone depth of the floor strata in the working face, and the plastic zone extends to floor mudstone and fine-grained sandstone with a depth of about 3.6 m. According to the types of water-conducting cracks in the floor strata of the test working face 11607 in Daizhuang Coal Mine, the floor strata are divided into the floor intact area, the structure developed area and the floor weak area, and according to the different zones of the floor, the technical measures to prevent and control the floor failure in the paste filling working face are proposed. The failure depth of the floor of the test working face was detected by the on-site water injection test method, and the results showed that the maximum failure depth of the floor of the test working face was about 3 m.