Comparative analysis of stress wave propagation and rock damage evolution in water versus air medium decoupled blasting

Decoupled charge structures fundamentally influence blasting performance in mining operations. Unlike previous studies that focused on single-medium conditions or limited decoupling ranges, this study provides the first systematic three-dimensional comparison of water and air medium decoupled blasting across decoupling coefficients of K = 2-6, integrating stress wave propagation, damage evolution, and fractal analysis within a unified computational framework. Results demonstrate that water-medium decoupled charges exhibit a pronounced "energy transfer amplification effect," generating circumferential stress peaks that are twice the magnitude of air-filled charges while more than doubling the effective stress duration. With increasing decoupling coefficients, stress attenuation indices decrease following a power-law relationship, with water-medium values (0.87-1.33) consistently higher than air-medium values (0.53-1.06). A significant "near-zone suppression and far-zone promotion effect" occurs when K increases from 1 to 2, reducing the crushed zone by approximately 60% while slightly expanding the fractured zone. Quantitative damage analysis reveals that water-medium charges produce substantially larger effective damage areas than air-medium charges under identical decoupling conditions. Fractal analysis indicates that crack networks formed under water-medium decoupling possess higher fractal dimensions (1.33-1.55) compared to air-medium conditions (1.17-1.46), signifying more complex and uniform fracture structures. These findings elucidate the mechanisms underlying water-medium decoupled blasting's superior performance and provide theoretical guidance for optimizing charge structures in mining operations.