The one-time completion blasting technology for blind shafts is widely used in underground mining, for safety reasons. Efficient blind shaft excavation relies on reasonable cutting blasting technology. To optimize blasting parameters, the impact of explosion stress waves and gases on rock fragmentation is quantitatively analyzed using explosion stress wave theory. A calculation model for the radius R₁ of the crushed zone and the radius R₂ of the fractured zone in rock under the combined action of borehole cutting stress waves and blasting gases is derived and established. Combined with practical engineering examples and the determination method of compensation coefficient C_f, three types of linear cutting patterns, namely six-hole bucket cutting, seven-hole bucket cutting, and nine-hole bucket cutting, are designed. The post-blasting cavity volume and crack length of these three different cutting methods are calculated and analyzed using numerical simulation. Quantitative description of the distribution pattern of blasting-induced cracks in the simulation results of three cutting methods using the box-counting fractal dimension method are presented. Based on this analysis, the nine-hole bucket cutting is selected as the optimal scheme and validated through field application of cutting blasting. The results indicate that the nine-hole bucket cutting blasting scheme for one-time completion of blind shafts, with a designed hole depth of 8 m and a blasthole utilization rate of 93.7%, is an efficient and reasonable technical solution.

To investigate damage range and damage degree of PMMA under different decoupling charge coefficients ( K ) after blasting, a reasonable range of decoupling coefficient was theoretically determined. Experimental images after blasting were obtained through two-dimensional (2D) model experiment. Algorithms for computing damage variables and fractal dimensions of cracks in different zones were developed in MATLAB software, and the relationship between fractal dimension and blasting damage was established. The results indicated that as the decoupling coefficient increased, the length of the longest primary crack and the total length of cracks decreased gradually. Damage variable ( ω ) of the decoupled charge blasting decayed exponentially with increasing distance, ultimately approaching zero. Meanwhile, the attenuation rate increased with increasing decoupling coefficient. The relative sizes of fractal dimensions based on the box-counting dimension algorithm correlated with the macroscopic damage variables. Fractal dimensions in the blasting zones I, II, and III decreased sequentially as the decoupling coefficient increased, resulting in an overall reduction in overall fractal dimension. A prediction model for blasting damage in PMMA material under model experiment conditions was established. The calculated blasting damage degree based on fractal dimension can be used to quantitatively evaluate the spatial distribution characteristics of blasting-induced cracks, which provides a new approach to study the evolution patterns of blasting damage of rocks.