Process research and application of axial roof cutting technology of abrasive jet and fracture

The large area overhanging of thick and hard roof is one of the critical reasons for inducing coal burst. Because of the shortcomings of deep borehole blasting and conventional hydraulic fracturing for the overhanging roof, the axial roof cutting technology of abrasive jet was developed. This technology achieves the best pressure relief by implementing prefabricated axial fractures and directional hydraulic fracturing in the roadway roof borehole to create an artificial fracture network in the roadway direction and tendency direction that is most conducive to roof collapse. The field application shows that the electromagnetic wave absorption ability of the stratum was enhanced, and the apparent resistivity was increased after the axial cutting roof technology of abrasive jet was implemented. During the mining operation of working face, the stress condition of the support was improved, and the release of micro-seismic energy was more stable, effectively reducing the risk of coal burst. On the basis of site observation, the mechanism of coal burst prevention by axial roof cutting of abrasive jet was revealed, that is, the plate-like structure fixed on both sides near the working face end is damaged by axial roof cutting, reducing the basic static load E_j, which is converted from the bending elastic energy of roof into the compression elastic energy of roadway surrounding rock, and reducing the strong additional dynamic load E_d, which is generated by the sudden fracture of roof, so that the roadway surrounding rock does not have the loading conditions for starting coal burst.