Research and application of combined pressure relief technology of roof hydraulic fracturing and deep hole blasting

In order to realize the smooth collapse of high-strength composite roof in 1311 working face of Zhaozhuang Coal Industry company and avoid strong ground pressure disaster caused by large-area roof suspension, firstly, the composite pressure relief mechanism of “cross cutting and longitudinal explosion” is analyzed theoretically, in other words, the secondary propagation radius r of blasting crack is greatly increased on the basis of fracturing damage length R and explosion crack radius a0, which improves the effect of roof pre-cracking, then, based on the industrial test of 1309 working face, the pressure relief process parameters of “cross cutting and longitudinal explosion” are reasonably determined and applied in the field. The results show that: the “cross cutting and longitudinal blasting” composite pressure relief process can increase the density of borehole axial fractures and borehole radial fractures, and the roof separation of roadway in the application area is low; it shows that the “cross cutting