Damage and Fractal Analysis of Double-Hole Blasting

To investigate the damage and failure characteristics of the double-hole blasting medium, theoretical analysis and model experiments are conducted in this study. Based on the analytical solution of the elastic plane strain problem in the double-hole blasting model, a theoretical model is established to study the evolution of the dynamic stress field during double-hole blasting. The damage of double-hole blasting with different blast hole spacing is studied by the model experiment; the damage in different regions around the blast holes is analyzed by partitioned research and fractal dimension quantification. The study shows that as the blast hole spacing increases, the super position effect of stress waves decreases, the radius of the crushing zone and the average length of the main crack gradually increase, the number of cracks decreases first and then increases. Additioanlly, the increase of blast hole spacing lead to gradual decrease of the damage along the direction of the blast hole connection, while the damage perpendicular to the direction of the blast hole connection gradually increases. Small hole spacing is conducive to the penetration of cracks between holes and promotes cracks expansion along the direction of the blast hole connection. With increasing blast hole spacing, the damage variable in the left and right regions of the specimen gradually increases, and reaches a minimum value in the central region when the blast hole spacing is 50 mm. The damage variables in area Ⅰ and area Ⅱ first decrease and then increase, while the damage variable in area Ⅲ gradually decreases. The damage variable distribution in the polar coordinate system shows that area Ⅰ exhibits a uniform damage pattern, and area Ⅱ gradually transitions from an elliptical to a circular distribution. Based on the relationship between the fractal dimension of the damage area and the damage variable, a fractal damage model for double-hole blasting of poly(methyl methacrylate) (PMMA) material is constructed.