Advancements and future prospects in the fundamental theories of rock blasting research Ⅳ — Damage evaluation

The critical aspect of roadway blasting contour is perimeter blasting. The effectiveness of perimeter blasting has a significant impact on both the quality of the blasting contour and the extent of damage to the surrounding rock. Drawing upon fractal theory, a comprehensive evaluation system encompassing "macroscopic - mesoscopic - microscopic" and "point - line - surface - cube" dimensions has been established. The "three scales" evaluation system is founded on the geometric scale of damage. The macroscopic scale (geometric scale > 10-3 m) assesses the degree of rock fragmentation; the mesoscopic scale (geometric scale: 10-6 ~ 10-3 m) evaluates crack propagation range; and the microscopic scale (geometric scale < 10-6 m) examines microscopic fracture morphology. The "four dimensions" evaluation system is based on the spatial distribution of damage. Point refers to CT scanning conducted on a rock core, line pertains to borehole imaging inside surrounding rock, surface relates to blasting contour quality, and cube involves cross-hole acoustic wave testing within surrounding rock. The implementation of the " three scales and four dimensions" evaluation system enables an accurate assessment of both the degree and extent of blasting damage. This approach holds significant guiding importance for elucidating the mechanisms underlying blasting damage and for achieving precise control over such damage.