Plasma blasting rock breaking technology is characterized by green, high efficiency, controllability, and has a good application prospect in deep rock breaking. In order to provide a new rock-breaking method for the rock-breaking engineering under deep stress, four groups of plasma sandstone blasting tests under different peripheral pressures were carried out. The morphology, structure and distribution of three-dimensional cracks inside the rock were comparatively analyzed by CT scanning and three-dimensional reconstruction, so as to study the effectiveness of the plasma blasting technology in rock breaking under different peripheral pressures. Meanwhile numerical simulation was conducted by using LS-DYNA to establish the plasma equivalent explosive model, supplementing the verification of the role of plasma blasting in the coupled stress field, and investigating the mechanism of plasma blasting under different pressures, as well as the internal crack expansion, distribution and damage evolution laws in the rock body in the blasting process. The results show that under the same voltage, with the increase of the 3D peripheral pressure, the number and distribution range of cracks on the surface of the rock exhibit a trend of gradual reduction, while the complexity of the cracks within the sandstone and the depth of penetration are significantly reduced. Due to the dynamic stress field generated by plasma blasting and the static stress coupling field generated by the surrounding pressure, the shock wave generated by the plasma blasting in the initial stage of the explosion plays a major role for the effect of different pressures under the action of the rock crack morphology and the center of the expansion of the region does not show obvious differences. With the attenuation of the shock wave, the 3D surrounding pressure in the middle and late stages of the plasma blasting process plays a decisive role in inhibiting the cracks of the rock mass expansion and damage evolution. At the same time, with the increase of the surrounding pressure, the more significant inhibition effect on the expansion of cracks in the rock body, resulting in the body fractal dimension and damage degree of 3D cracks in the rock body, while the role of the surrounding pressure approximately follows a linearly decreasing relationship.

Deep coal rock blasting poses high risks, and hydraulic fracturing faces limitations, necessitating the development of controllable rock-breaking technologies. As an advanced high-energy gas fracturing technique, high-energy gas-generating agents demonstrate remarkable advantages in rock fragmentation, providing robust technical support for efficient and safe coal mining. This study focuses on the casing materials of high-energy gas-generating agents, investigating their impact on borehole wall pressure during coal rock fracturing. A comprehensive pressure monitoring system was established, employing three casing materials—transparent PVC (polyvinyl chloride), white PVC, and kraft paper tubes—for borehole wall pressure experiments. Attenuation indices and reliability were selected as evaluation metrics to analyze the influence of material physical properties on borehole wall pressure. Results indicate that the initiator, upon ignition, generates stress waves and a small amount of gas. The stress wave induces the first pressure peak, followed by a decline due to gas diffusion. The superposition of reflected stress waves and gas expansion waves forms the second peak, while gas expansion variations produce the third peak. Without the main agent, the initiator group exhibits the lowest pressure peak, shortest pressure rise time, minimal loading rate, limited energy release, and low transmission efficiency. For the three groups containing the main agent, pressure peaks near the high-energy gas-generating agent (10 cm away) approximate 200 MPa, with pressure rise times around 20 ms. The attenuation coefficients of pressure peaks for the three casing materials from the biggest to the smallest follow the order: transparent PVC, white PVC, and kraft paper tube. The attenuation coefficients of pressure rise times from the biggest to the smallest rank as: transparent PVC, kraft paper tube, and white PVC. For loading rate attenuation coefficients, the sequence from the biggest to the smallest is: white PVC, transparent PVC, and kraft paper tube. Because of its high elastic modulus and low Poisson’s ratio, white PVC casing demonstrates optimal performance in pressure peak, rise time, and loading rate near the high-energy gas-generating agent, achieving the highest energy transmission efficiency. Transparent PVC casing exhibits higher pressure peaks and loading rates than the paper tube near the agent but underperforms at longer distances, indicating strong directionality and concentration. The kraft paper tube ensures uniform energy distribution but exhibits the weakest overall energy concentration, along with the longest rise times and lowest loading rates. These findings provide a theoretical foundation for optimizing high-energy gas-generating agent designs and enhancing rock-breaking efficacy.

In order to study the microscopic damage characteristics of marble by explosive impact loading, we carried out the blasting test of marble with different charges, analyzed the microcrystalline structure of marble specimens before and after blasting by X-ray diffraction and image processing techniques, predicted the location of crack initiation and direction of expansion according to the difference of mineral components, counted the parameters of microcrystalline structure, and explored the mechanism of microscopic impact of explosive impact loading on the structure of marble. The results show that: the diffraction peaks of calcite and quartz minerals in the mineral composition of marble have a high degree of overlap with those of marble, and the effect of magnesite on the diffraction peaks of marble is the smallest; the increase of the explosive impact load destroys the crystal distribution of marble minerals, and the lattice spacing slightly decreases, and the microcrystalline structure becomes more compact. The intensity of the diffraction peaks before the impact is larger, and the difference in the intensity of the diffraction peaks is obvious; after the impact, the other stronger diffraction peaks are more uniform, and the difference between them and the strongest peaks is gradually shrinking; the physical damage caused by blasting impact and the localized weakening area formed by selective particle migration are called the priority locations for the initiation of blasting cracks. For marble, which is more prone to tensile failure in areas with relatively high content of periclase, the stress concentration generated leads to the appearance of small cracks and holes, affecting the initiation and propagation direction of blasting cracks.The diffraction angle in the microcrystalline structure has a relatively stable limiting threshold, and when the size of the diffraction angle is close to this threshold, the effect of the blast impact load on the diffraction angle gradually decreases, and the impact load has the greatest effect on the half-peak width of the calcite in the marble. The research results will provide theoretical basis for the rock damage destruction under blasting action and the stability assessment of blasting engineering.

This study investigates how different carbon-containing absorbents affect the transient phase change expansion of liquid oxygen. Specifically, we prepared 3 types of liquid oxygen charges with varying carbon contents (0, 0.1 g, and 0.2 g). A high-speed schlieren system and an overpressure measurement system were used for comparative analysis on the propagation patterns of gas precursor and phase change products in the schlieren flow field and the intensity changes of the phase change gas pressure. Both theoretical and experimental analysis were conducted to unveil the propagation patterns, evolution process and pressure distribution of the phase change gas in the air flow field. Results show that ① Carbon content exerts a significant regulatory effect on phase change expansion. As the carbon content increased from 0 to 0.2 g, the initiation time increased from 1.32 ms to 3.69 ms, and the cumulative pressure time increased by 180 %. ② The propagation speed of the gas precursor exhibited significant increase, with maximum horizontal speed rising from 473.96 m/s to 692.71 m/s and vertical speed from 875.00 m/s to 1 604.17 m/s. ③ Peak overpressure showed nonlinear growth, with axial overpressure increasing from 7.754 MPa to 16.567 MPa and radial overpressure from 1.301 MPa to 4.838 MPa. ④ Separation time between the gas precursor and the phase change products increased from 60 μs to 110 μs. Vertical displacement generally exceeded horizontal displacement, showing an anisotropic propagation pattern of "rapid vertical expansion and slow lateral spread".