To explore the influence of ignition position change on overpressure characteristics of methane/air premixed explosion under different equivalence ratios, several tests with varying length-to-diameter and equivalence ratios on the rise rate of peak overpressure and positive pressure duration were carried out through a self-built explosion test system. The main influencing factors affecting the pressurization characteristics of methane/air premixed explosion were analyzed by the dimensional analysis method, and the calculation formulas of rise rate of overpressure peak and positive pressure during methane/air premixed explosion were proposed. The results show that the rise rate of the overpressure peak increases with the increase of the equivalence ratio, and the increase in length-to-diameter ratio makes the rise rate decrease gradually, which is different from the attenuation rate. The positive pressure duration is gradually prolonged with the rise of the length-to-diameter ratio. However, the maximum positive pressure duration corresponds to different equivalence ratios with the length-to-diameter ratio changes. Furthermore, the calculation formulas of the rise rate of overpressure peak and positive pressure duration of methane/air premixed explosion are obtained by the dimensional analysis method, and the feasibility of the formulas is verified by comparing the experimental values with the theoretical values. It was found that methane/air premixed explosion is significantly affected by the ignition position and equivalence ratio, which can provide a reference for the power evaluation and safety control of methane explosions.

Blasting excavation generates transient P-waves that significantly impact tunnel stability. For water-filled diversion tunnels, the dynamic response of the surrounding rock differs from conventional dry tunnels. Most existing analytical studies focus on the steady-state solution and single-lined tunnels, rarely accounting for composite linings or the presence of water. This paper investigates the transient stability response of deep-buried circular composite lining diversion tunnels under transient P-wave disturbances. The fluid within the tunnel is treated as a distinct medium, and the tunnel-lining interface is considered a non-ideal contact surface. By applying Fourier synthesis, wave function expansion, and trapezoidal quadrature formula, an analytical solution is derived. Validation through comparison with existing literature demonstrates the method's effectiveness. The study analyzes the effects of Poisson's ratio of surrounding rock, the non-ideal interface's elastic coefficient, and the disturbance's loading duration on the dynamic stress concentration coefficient. Results indicate that the compressive stress concentrations occur at the roof and floor, while tensile counterpart concentrations appear at the two sidewalls during dynamic disturbance. As Poisson's ratio increases, there is a transition from tensile to compressive stress concentration, with a gradual degree in compressive stress intensity. Poor contact between the rock mass and liner induces oscillations in the stress time-history curve. The dynamic response converges accordingly as the elastic coefficients of an imperfect interface approach those of a perfect interface. With increasing blasting load duration, peak dynamic stress around the roof and floor initially rises, then stabilizes, while stress at the sidewalls initially decreases before leveling off.

Pre-splitting blasting has been widely employed in river channel slope excavation to effectively mitigate damage to the retained rock mass, reduce blast-induced vibrations, and optimize blasting parameters for water-saturated slopes. Investigation of reasonable parameters for pre-splitting blasting in such conditions is important for river channel excavation projects. Based on geometric, physical, and dynamic similarity principles, an experimental model for pre-splitting blasting water-saturated slopes was designed, utilizing concrete as a substitute for red sandstone and detonators instead of emulsified explosives. The quality of pre-split crack formation, slope face shaping, and retained rock mass damage were evaluated under various conditions. The results showed that the pre-split crack formation quality and slope shaping quality significantly improved. The damage to the retained rock mass was reduced by 24.86% when the hole diameter increased from 0.8 cm to 1.2 cm. Field test results indicated that the optimal blasting effect can be achieved with a pre-split hole diameter of 115 mm and a hole spacing of 80 cm in a practical application of pre-splitting blasting for water-saturated slopes when the geological conditions involve medium-hard rocks.

Pre-split blasting has emerged as a crucial technique for enhancing the permeability of low-permeability coal seams and improving gas drainage efficiency. While extensive research has focused on the effects of factors such as blast hole configuration, charge structure, charge coefficient, explosive quantity, and the propagation dynamics of blasting stress waves, limited attention has been given to fracture expansion characteristics through numerical simulations. Furthermore, experimental investigations into crack propagation remain scarce. This study addresses these gaps by examining low-permeability coal samples from a specific mine, employing small-dose coupled charge blasting technology combined with computerized tomography scanning technology. The experimental approach enabled the acquisition of macroscopic damage characteristics and three-dimensional crack distribution patterns post-blasting, facilitating an in-depth analysis of internal crack expansion under blasting stress. Key findings demonstrate the feasibility of utilizing detonating explosives instead of conventional explosives for small-scale coal sample blasting experiments with low-dose coupled charges. The results reveal that: (1) a larger blast hole diameter correlates with diminished crack propagation and permeability enhancement under constant charge quantity and tamping pressure; (2) tamped charges outperform loose charges when blast hole diameter and charge quantity are held constant; (3) an optimal charge quantity exists for fracture propagation, with excessive amounts proving counterproductive. Specifically, for the standard-sized low-permeability coal samples examined, a charge quantity of 25 mg yielded optimal results, producing a crack volume ratio of 12.79% and a single crack volume of 20 135.03 mm, followed closely by a 20 mg charge.

To investigate the energy evolution and failure patterns of magnetite during blasting and to minimize the impact of blasting disturbances on the stability of pillars and surrounding rocks, a series of multi-stage strength impact tests were conducted on magnetite samples using a Split Hopkinson pressure bar (SHPB) apparatus. The dynamic response characteristics of magnetite were analyzed, focusing on parameters such as dynamic peak compressive strength, failure modes, fragmentation size, and energy dissipation density under varying strain rates. The results show that magnetite's dynamic peak compressive strength and energy dissipation density increase exponentially with the increase in strain rate. At the same time, the crushing size decreases exponentially, demonstrating a strong strain-rate dependency. The failure process of magnetite can be divided into three stages: crack compaction, elastic deformation, and crushing. The dynamic increase factor (DIF) also increases with the increase in strain rate. The failure mode of magnetite transitions from splitting failure at lower strain rates to crushing failure at higher strain rates as crack interactions intensify. Therefore, when blasting rock breaking is applied to magnetite mining, it is crucial to balance impact strength and energy dissipation to enhance crushing efficiency while meeting the required fragmentation standards.

During aero-engine casing containment tests, the explosive separation method used to achieve the constant-speed fly-off of titanium alloy blades often produces a bright titanium fire phenomenon. This titanium fire obstructs high-speed camera recording of the blade fly-off process. To address this issue, this study analyzed the mechanism of titanium fire generation and proposed a barrier layer method to suppress titanium fire during shaped energy cutting of titanium alloys. Numerical simulations using the Euler algorithm in AUTODYN were conducted to evaluate the blocking effect of the barrier layer and its feasibility for titanium fire suppression. Experimental investigations were then performed to quantitatively assess the brightness reduction of titanium fire, comparing the effectiveness of four barrier materials. The results indicate that 0.1mm thick aluminum and titanium tin foil achieve titanium fire suppression rates of 29.5% and 24%, respectively, demonstrating moderate effectiveness. A 0.1 mm thick copper sheet shows poor performance with a suppression rate of only 4.3%, while a 0.1 mm thick aluminum silicate coating exhibits the best performance, achieving a suppression rate of 70.9%. This study has summarized the mechanism of titanium fire suppression suing barrier layers during shaped energy cutting of titanium alloy plates and validated the feasibility of the barrier layer method. The findings can provide a practical approach for titanium fire elimination in explosion separation processes involving shaped energy cutting of titanium alloys.

The occurrence of oversized fragments during blasting operations significantly increases the cost of blasting, crushing, and hauling expenses. This study addressed the slab' phenomenon observed in the blasting of intact hard rock at the Pingtanyuan Pumped Storage Power Station, where the oversized fragments of the surface blasting area was up to 6 m×5 m×2.5 m. Through comprehensive mechanism analysis, the investigation indicated that the quality of the stemming was the key reason for forming large fragments at the upper part. Meanwhile, the mechanism of its influence lies in the over-long stemming length of the original blasting scheme, which resulted in a low charge center, leading to insufficient energy distribution at the top of the blast hole. Furthermore, an oversized blasting fragments control measurement based on stemming quality optimization was proposed. The stemming length was optimized from 3~4 m to 2.1~2.4 m using a time-sharing piecewise calculation method and the optimization principle, which allowed the part of the stemming structure to rush out of the blast hole. Besides, the decontaminated rock chips were used as stemming material. The results show that the optimized scheme prevented the occurrence of the slab phenomenon, significantly reduced boulder rates, and saved rock breakage costs.

As a main mean of open-pit mining, bench blasting is still an irreplaceable production method at present and even in the future. By deeply analyzing the measured data of bench blasting and using 3DEC software to simulate the bench blasting process, the internal rock mass movement trajectory and muckpile distribution during the bench blasting process were revealed. The research results show that the monitoring points generally rose along the vertical direction first and then fell during the blasting process. Among them, the movement of the monitoring points on the upper part of the monitoring hole were more obvious in the vertical direction, rising to a certain height and then quickly moving vertically downward. While the monitoring points on the lower part of the monitoring hole mainly moved forward in the horizontal direction, and the vertical direction movement is relatively weak. At the same time, in order to study the spatial distribution of the muckpile, the bench in the research area were divided into six parts, as Ⅰ~Ⅵ. Besides, the main part (0~40 m) of the muckpile was divided into four regions, as A, B, C and D. According to the simulation results, it can be found that the Ⅴ rock mass accounts for the most in region A (muckpile 0~10 m), which is as high as 41.7%. The Ⅰ~Ⅴ rock mass distribution is relatively even in region B (muckpile 11 m~20 m). The Ⅰ~Ⅲ rock mass accounts for 43.1%, 37.5% and 19.3%, respectively, and the Ⅳ rock mass accounts for a very small part in region C (muckpile 21~30 m). It is basically composed of the Ⅰ rock mass in region D (muckpile 31~40 m) at the forefront of the blast muckpile, which accounts for 95%.

A large-area concrete site was prepared to eliminate the boundary effects to investigate the propagation law of detonation-induced cracks in differential blasting under varying hole spacing. Multiple sets of linear three-hole and cross-five-hole model tests were conducted using electronic detonators and detonating cords as the blasting sources. The propagation length, direction, and crack arrest position of detonation cracks were recorded under different blasting parameters. The key factors affecting crack propagation were identified by combining the experimental results with the theory of sequential controlled blasting. The results indicate that in the three-hole model, a through-crack forms between the blast holes when the middle hole detonates first, followed by the two side holes. However, as the hole distance increases, the crack becomes increasingly irregular. When the distance reaches 25 times the hole diameter, the crack fails to penetrate and no longer propagates along the direction of the blast holes. In the cross five-hole model, a through-crack can only form when the spacing is within 20 times the hole diameter. The crack generated by the first blast tends to propagate towards the nearest subsequent hole. Still, it does not follow a straight path, exhibiting deflection due to the influence of the additional holes. Therefore, to achieve straight cracks along the contour surface in practical engineering, it is crucial to adjust the timing and control blasting parameters based on specific hydrogeological conditions to fully utilize the void effect and the detonation timing difference.

A novel energy dissipation blasting technique based on water coupling is proposed to explore new methods for rapid excavation of spillway protection layers in hydropower stations under relatively intact hard rock conditions. This method specifically addresses the excavation requirements of the Nam Kong 1 Hydropower Station spillway in Laos. By increasing borehole pressure, the technique generates stronger stress, which is advantageous for excavating hard rock formations. Simulation analysis using LS-DYNA software demonstrates that coupling water-charged explosives with a blocked borehole bottom amplifies the peak load on the borehole walls and extends the explosive load duration, thereby improving the fragmentation of harder rock at the borehole bottom. Results indicate that the combination of bottom-hole blockage and water-coupled charges increases lateral damage depth and prolongs load application time, thus achieving more effective excavation and formation in relatively intact hard rock. Comprehensive evaluations based on numerical simulations and field test parameters confirm that this approach significantly improves the quality of excavation and formation of the first-stage stilling basin floor in practical engineering applications.