Stress wave attenuation by roof-cutting pre-splitting in deep coal mine roadways: Mechanism and experimental validation

Dynamic disasters induced by rock mass instability under deep mining conditions constitute a major geotechnical challenge, particularly in coal mine roadways excavated beneath ultra-thick hard roofs. Under these conditions, stress waves induced by dynamic disturbances, including hard-roof fracture and fault slip within the stope, propagate through the coal-rock mass and interact with high static stresses, ultimately triggering rockburst disasters. Roof-cutting pre-splitting technology can form a pre-splitting surface to attenuate stress wave propagation and reduce the intensity of dynamic loading. However, the attenuation behavior of rockburst-induced stress waves across the roof-cutting pre-splitting surface remains unclear. This study integrates theoretical analysis with laboratory tests to investigate the energy evolution mechanism of rockbursts in a fully mechanized top-coal caving face of an extra-thick coal seam. A four-stage energy evolution model, including energy accumulation, energy release, stress wave propagation, and roadway failure, is proposed to explain the attenuation of stress wave propagation by the pre-splitting surface in the stope. A joint stiffness model incorporating stress wave transmission and reflection is then established to evaluate the effect of the angle between the pre-splitting surface and the incident stress wave on stress wave transmission. In addition, creep tests with impact disturbance are conducted to quantify stress wave attenuation at different pre-splitting surface angles. The results indicate that the roof-cutting pre-splitting surface significantly affects fracture evolution characteristics under impact disturbance. The pre-splitting surface weakens stress wave transmission mainly through tangential plastic deformation, thereby reducing the impact energy transferred to the roadway roof. For incident angles of 90°, 75°, 60°, and 45° relative to the pre-splitting surface, the ratios of transmitted wave energy to incident wave energy are 52.5%, 42.2%, 39.9%, and 29.8%, respectively. As the incident angle decreases from 90° to 45°, the energy attenuation effect of the pre-splitting surface is markedly enhanced, and the failure mode of the rock mass gradually shifts from compression-dominated fracture to shear sliding along the pre-splitting surface. For engineering applications under similar deep mining conditions, the roof-cutting angle is recommended to be no less than 60°.