Blasting excavation of rock masses under high in-situ stress often encounters difficulties in rock fragmentation and a high boulder rate. To gain a deeper understanding of this issue, the stress distribution of rock masses under dynamic and static loads was first studied through theoretical analysis. Then, the ANSYS/LS-DYNA software was employed to simulate the blasting crack propagation in rock masses under various in-situ stress conditions. The fractal dimension was introduced to quantitatively analyze the influence of in-situ stress on the distribution of blasting cracks. The results indicate that in-situ stress primarily affects crack propagation in the later stages of the explosion, while crack initiation and propagation in the early stages are mainly driven by the explosion load. In-situ stress significantly influences the damage area and fractal dimension of cut blasting. Under hydrostatic in-situ stress, as the in-situ stress increases, the damage area and fractal dimension of blasting cracks gradually decrease. Under non-hydrostatic in-situ stress, when the principal stress difference is small, in-situ stress promotes the damage area and fractal dimension of the surrounding rock, enhancing rock fragmentation. However, when the principal stress difference is large, in-situ stress inhibits the damage area and fractal dimension of the surrounding rock, hindering effective rock breaking.

To precisely control the tunnel smooth blasting effect, this study conducts both model experiments and numerical simulations to investigate the impact of shaped charge jet initiation on emulsion explosives and surrounding rock damage fractal characteristics under different ratios of the main-to-secondary charge lengths (L₁/L₂). The study also includes field validation. The results indicate the following: (1) The Arbitrary Lagrangian–Eulerian (ALE) method can accurately reproduce the formation, motion, impact, initiation, and dynamic damage evolution of a shaped charge jet inside a blast hole, with a deviation of less than 6.4% compared to high-speed photography observations. (2) Under the working conditions in this study, when an axial aluminum energetic liner and two-stage air-segmented charge in the peripheral holes are used, the fractal dimension (D_f) initially increases from 1.57 to 1.66 and then decreases to 1.41 as the L₁/L₂ ratio increases. (3) Field test results demonstrate that, when using a two-segment explosive charge with a 20 cm gap between segments and an L₁/L₂ ratio of 2, the average over- or under-excavation is controlled within 7 cm, with the maximum deviation not exceeding 12 cm. The corresponding average fragment size (d₅₀) is minimized, resulting in an excellent smooth blasting effect and effectively controlling the fragmentation of the smooth blasting layer. The conclusions of this study provide valuable insights for the development of advanced shaped charge blasting techniques.

The propagation of stress waves and the evolution of blasting-induced cracks in discontinuous rock mass are strongly influenced by joint characteristics. This study focuses on intersecting-joint rock mass and employs the explicit dynamic finite element method with the RHT constitutive model to simulate blasting. The effects of joint thickness and angle on stress wave behavior and crack propagation were systematically analyzed, and fractal theory was applied using MATLAB 2023b to quantitatively characterize crack distribution. The results indicate that joint thickness significantly affects stress wave transmission and reflection: thicker joints enhance reflected wave intensity while attenuating transmitted waves due to successive reflections within the infill. Joint angle controls the number of reflections between joints, with smaller angles producing stronger interactions. Thickness and angle jointly govern crack propagation, causing cracks to concentrate between the borehole and joints. Thickness primarily determines crack density on the blast-facing side of horizontal joints, whereas joint angle exerts deflecting and inhibiting effects. Fractal analysis shows that the fractal dimension of cracks varies nonlinearly with joint characteristics, with higher values in the borehole-to-joint region, increasing with thickness and angle. These findings provide quantitative insight into stress wave–joint interactions and guidance for optimizing blasting design in jointed rock mass, helping to minimize overbreak and underbreak and improve excavation safety.

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.

The eccentric non-coupled explosive loading structure is widely present in engineering rock blasting. The mechanism of its influence on the blasting effect and energy utilization still needs in-depth research. This paper establishes a theoretical model of peak pressure on the borehole wall for the eccentric non-coupled explosive loading structure and uses the ANSYS/LS-DYNA numerical simulation method to study the influence law of different radial non-coupling coefficients K on the damage characteristics of the rock mass. It also quantitatively analyzes the damage spatial distribution characteristics by combining the fractal theory. Finally, the theoretical and numerical analysis results are verified through field tests. The research results show: (1) The pressure distribution on the borehole wall of the eccentric loading structure is significantly asymmetric, and the pressure difference between the coupled side and the non-coupled side increases with the increase in K value; the error between theoretical calculations and numerical simulation results is less than 10%. (2) As the K value increases from 1.6 to 4.0, the damage areas and crack numbers of both loading structures decrease, but the eccentric loading structure always maintains a larger damage range on the coupled side. (3) Based on the fractal theory analysis, when K = 3.4–4.0, the rock mass damage spatial distribution is the most uniform, the standard deviation is the smallest, and the energy utilization efficiency is the highest. (4) The field test verification shows that when K = 3.75, the pre-splitting effect is the best, the half-hole rate reaches 85.7%, the wall surface flatness is controlled within ±5 cm, and compared with traditional methods, the cost is saved by 7% and the efficiency is increased by 45%. The research results provide an important theoretical basis and reference for the engineering application of the eccentric non-coupled loading structure.