Fracture evolution law and control technology of roadways with extra thick soft roof

The key point to solve the maintenance problem of roadways with extra thick soft roof is to understand how the fracture evolves in surrounding rocks. To research the fracture evolution law of panel 15107 in Huangyanhui Coal Mine, multi-parameter monitoring methods including the borehole imaging, geo-radar and roof separation monitoring are applied at the mining site. Universal Distinct Element Code (UDEC) was employed to research the fracture evolution and deformation characteristics with different thicknesses and strength of mudstone roof. The result shows the process of the propagation, the crack-opening and the separation characteristic of this type of roadway is a dynamic process gradually developing upwards. In the anchored zone, the fracture is fully developed and is severely separated and crushed. During the mining process, the separation is relatively small and the load of bolts is stable in the anchored zone, but the load on the cables increase rapidly. Based on the above result, the author proposed a new support principle that intensifies the roof strength, and controls the ribs and the roof together. The support method of the high-strength bolt-beam-net, the high density cable and the cable-grout technology is applied in the roadway support, which is effective in maintaining the roadway stability.