Analysis on the mechanism and effect of coal seam water jet reaming and grooving technology for prevention and control of rock burst

Aiming at the limitations of small pressure relief range and short pressure relief time of boreholes in rock burst coal seams, water jet reaming and grooving technology was developed. The technology creates a large-scale pressure relief cavity through high-pressure water jet rotary cutting drilling, promoting the stress transfer and energy dissipation of surrounding rock, thereby reducing the rock burst risk. Combining theoretical analysis, numerical simulation, and field measurement, this study investigates the rock burst prevention mechanism and validates it through on-site application. The results indicate that the water jet rotary reaming causes the surface damage of the coal body through the water hammer pressure, and uses the stagnation pressure to continuously break the coal mass via water hammer pressure, while the subsequent stagnation pressure continuously fractures the coal through shear and tensile actions. The synergistic effect of these two stages significantly increases the borehole diameter. The mechanism of prevention and control of rock burst of water jet reaming and grooving coal seam is as follows: the huge cavity formed by grooving increases the range of coal fracture zone and plastic zone, makes the bearing pressure transfer to the deeper part, and reduces the overall static load level of near-field surrounding rock; meanwhile, the weak structure formed in the large-scale crushing zone increases the dynamic load attenuation ability and reduces the dynamic load disturbance level caused by the far-field roof breakage. After the field engineering test, compared with the conventional drilling relief with large diameter, the coal stress and surrounding rock deformation in the water jet reaming and grooving area are significantly reduced, and the pressure relief effect is significantly improved.