Research on unloading technology of coal pillar by high-pressure abrasive jet for lateral cutting hard roof

Aiming to solve the problems of high stress concentration, large deformation, and difficulties to support in the gob-side roadway under a hard roof, the energy distribution of abrasive jet was analyzed. Impacts and rock breaking effects of abrasive particles and high-pressure water jet were investigated. Based on the principle of "masonry beam", the periodic fracture mechanics model of rock strata under different lithological conditions was established. The fracture of the overlying rock layer under the condition of lateral cutting roof of the roadway was studied. The stress change of the coal pillar before and after the cutting roof was analyzed by numerical tools. Unloading technology of coal pillar of the abrasive jet lateral cutting roof was developed. The field test results show that the height deformation of the roadway is reduced by 38.7% and the width change is reduced by 45.8%. The roadway deformation is effectively controlled after the abrasive jet cutting roof treatment. At the same time, the maximum daily total energy is reduced by 85.5% and the average daily total energy is reduced by 82.6% after cutting roof. The weakening effect of abrasive jet lateral cutting roof on hard roof is certified. This study provides a new technical methodology for the weakening treatment of hard roof.