Laboratory blasting tests on granite were conducted under varying confining pressure conditions. Damage data across blast crater cross-sections in various directions were obtained using 3D laser scanning and image processing techniques and systematically analyzed based on fractal theory to characterize damage morphology and spatial distribution. The directional anisotropy of blast-induced rock damage was investigated, along with the spatial heterogeneity evolution of damage cross-sections in the direction of applied confinement. The research results indicate that confining pressure significantly regulates the spatial distribution of explosive damage in rock. Under no confining pressure, damage propagation is primarily governed by the intrinsic heterogeneity of the rock, resulting in an approximately isotropic distribution of blast-induced damage, as indicated by a low coefficient of variation of 0.159. Under asymmetric biaxial confining pressure, the cross-sectional damage exhibits a stress-direction-dependent deflection and a redistribution of damage complexity. This phenomenon is herein defined as the “inductive deflection” effect. Lower equal biaxial confining pressure enhances the dominant role of the rock’s heterogeneous structure in the damage evolution path, resulting in differences in the degree of damage across different directional cross-sections. Higher equal biaxial confining pressure suppresses the expansion of damage along the free surface and redirects damage development toward greater depths, resulting in a 21.4% increase in damage depth compared with unconfined condition. Meanwhile, the distribution of the fractal dimension becomes nearly isotropic, with coefficients of variation below 0.26. In the principal axis direction, as the cross-sectional position moves farther from the blast center, both the damage area and its fractal dimension exhibit an exponential decay trend ( R 2 > 0.83), reflecting the strong nonlinear characteristics of the energy attenuation process within the rock mass. This paper presents the physical significance of fractal parameters in the anisotropic analysis of cross-sectional damage: the fractal dimension \(D\) reflects the regulatory effect of confining pressure on the “propagation mode” of the damage, while the intercept \(A\) is directly related to the “spatial occupancy rate or coverage” of the damage. Both are crucial parameters for describing the effects of rock blasting and for assessing the regulatory role of confining pressure on explosive damage.
Gao et al. (Mon,) studied this question.