Improving Hard Rock Materials Cuttability by Hydraulic Fracturing at Mining Working Face

During advancing the working face at Guojiawan Coal Mine, hard rock faults are encountered, which hinder the normal cutting of the shearer. Hydraulic fracturing is applied to pretreat the hard rock materials. Un-directional hydraulic fracturing experiments in transparent gelatin samples are carried out. The influence of the differential stress, the borehole dip angle on the initiation and propagation of un-directional hydraulic fractures (HFs) are investigated. Three field test schemes of hydraulic fracturing are proposed and implemented at the 51207 working face of Guojiawan Coal Mine. Compared with the results of different test schemes, the cutting current ratio of the shearer is reduced by 51.70% and the cutting efficiency is increased by 89.93%. Therefore, the feasibility of hydraulic fracturing to improve the cuttability of the hard rock materials is verified, which provides a theoretical basis and field guidance for hydraulic fracturing pretreatment of the hard rock materials at a coal mining working face.