Differences in thickness, mineral composition, wave impedance, and joint fissures. This often leads to a mismatch between the charge structure of the pre-splitting and cutting holes and the physical and mechanical properties of the layers, which can easily cause the complex rock layers to fail to pre-split. The soft rock layers form chicken-nest-shaped explosive pits due to excessive consumption of explosive energy, making it difficult for pre-splitting and cutting holes to penetrate the entire length of the blast hole effectively. To attain consistent pre-splitting of the composite roof, the LS-DYNA software was employed to analyze the impact of the charging structure on the pre-splitting effect of the composite roof. Based on this foundation, a uniform-dispersion and pressure-holding pre-splitting blasting technique was proposed for the composite roof. Field experiments were conducted, and in conjunction with the preliminary evaluation of the progression of post-blast fractures, the viability of this uniform-dispersion and pressure-holding pre-splitting blasting method was substantiated. The research results indicate that the escape of explosive gas from hard rock layers to soft rock layers is the primary reason for the uneven energy utilization in the pre-cracking explosion of the composite roof. The composite roof uniform dispersion pressure pre-splitting blasting technology divides the pre-splitting holes into multiple chambers according to the layered structure of the composite roof. Each layer has an independent post-explosion pressure holding chamber, which meets the explosive energy requirements of each pre-splitting layer, thereby avoiding excessive consumption of explosive energy in soft rock layers and enhancing the pre-splitting effect in hard rock layers.

A study was conducted using explosive cutting cords to titanium alloy plates to quantitatively investigate the additional kinetic energy generated during blade fracture in aviation engine case inclusion experiments. The additional kinetic energy was analyzed through both computational and experimental approaches. Using AUTODYN software, two computational methods were employed: the center-of-mass motion method (yielding E1) and the particle-by-particle accumulation method (yielding E2). The accuracy of these methods was systematically compared. Experimental validation was achieved by measuring the additional kinetic energy (E3) in controlled explosion experiments. The computational results were verified against experimental data, confirming the reliability of both the simulation and testing methodologies. The study reveals that the maximum additional kinetic energy generated during the severance of titanium alloy plates constitutes a smaller proportion of the total kinetic energy proportion than the threshold proposed by the FAA company. These findings provide critical insights for designing and evaluating cartridge inclusion experiments in aviation safety applications.

To investigate the inhibitory effect of calcium carbonate on methane explosion in the presence of coal dust, experiments and numerical simulations were applied in this study. The inhibitory performance of calcium carbonate under various particle sizes and concentrations was analyzed, providing a theoretical basis for safety protection in high-risk environments, such as coal mines. By using a self-developed 9.6-meter-square straight pipe, the experiments were conducted with Calcium carbonate, whose particle sizes ranged from 6.5 to 74 micrometers, and the concentration levels were maintained within the optimal range of 100 to 200 g/m³. Based on this, the optimal particle size and concentration of calcium carbonate were determined by analyzing the pressure changes during the explosion process. The experimental findings reveal that the explosion process can be divided into four stages: initial methane combustion, subsequent methane combustion involving coal dust, calcium carbonate decomposition, and a final inhibition stage. Meanwhile, the calcium carbonate reduces oxygen concentration. It absorbs heat through thermal decomposition reactions, which slows down the combustion reaction rate and establishes local thermal equilibrium, thereby suppressing the propagation of the explosion. The calcium carbonate achieves optimal explosion suppression performance with a maximum pressure reduction rate of 46.7% at specific parameters: a calcium carbonate of 150 g/m³ combined with a particle size of 23 micrometers. Additionally, numerical simulations were employed to verify the experimental results, which demonstrate that the pressure change trends are consistent with the experimental results, with a relative error of less than 15%. As an effective explosion inhibitor, calcium carbonate demonstrates significant inhibitory effects on methane explosions in the presence of coal dust under specific particle size and concentration conditions. This study provides experimental and theoretical support for the application of calcium carbonate in industrial explosion protection.

To systematically reveal the influence of laws of microwave radiation parameters (power, time) on the degradation of the mechanical properties of iron ore and the energy dissipation mechanism, and to improve the crushing efficiency of iron ore, this iron ore from Sishanling in Liaoning Province is the research object. By adopting a method combining microwave pretreatment, multi-scale mechanical tests, and microscopic tests, this thesis conducts static and dynamic impact tests as well as XRD tests on iron ore samples under different microwave actions. By analyzing the mechanical properties of iron ore subjected to various microwave treatments and utilizing the principles of energy conservation, this study elucidates the damage evolution characteristics and the laws governing energy evolution of iron ore under the coupled action of microwave and mechanical forces. The research results show that: (1) With an increase in microwave power and irradiation time, the sample mass decreases slightly, and the longitudinal wave velocity, uniaxial compressive strength, and elastic modulus exhibit a linear degradation trend. Microscopic tests have confirmed that the damage is caused by thermal stress cracking, rather than a change in composition. (2) The analysis of energy evolution indicates that microwave pretreatment diminishes the total input energy density of the sample, reduces the proportion of elastic energy, and elevates the proportion of dissipated energy. This phenomenon suggests a deterioration in the ore's storage capacity and a transition toward plastic yielding. (3) Dynamic impact tests show that an increase in microwave damage leads to a 45.58% increase in reflected energy, a 16.12% decrease in transmitted energy, and an increase in energy dissipation to 37.49%.

To attain precise regulation of the smooth blasting effects during tunnel excavation, this paper employs the LS-DYNA fluid-solid coupling algorithm and a cubic polynomial ignition and growth equation of state to develop a numerical model of shaped charge jet initiation of explosives. A study on the optimal detonation distance for emulsified explosives within an axially shaped charge configuration was conducted. Additionally, field experiments on axial energy-focused charge structures were performed based on the tunnel blasting excavation project of the Hongshimen Tunnel on the Chengping Expressway (Beijing section). The research results indicate the following: (1) When employing the commonly used axial energy-focused charge structure in industry, approximately 25 cm of movement occurs at the tip of the energy-focused jet 110 μs after the main charge detonation. At this point, the jet separates from the plug. Subsequently, the energy-focused jet becomes discontinuous and fragmented during its motion, which may adversely affect the initiation of the explosive charge. Therefore, selecting an appropriate explosive spacing is crucial for the successful detonation of the initiated explosive by the energy-focused jet. (2) Based on the analysis of jet head pressure and explosive reaction characteristics, it is observed that when the explosive spacing exceeds 50 cm, the impact pressure exerted by the jet on the initiated explosive is less than the critical initiation pressure of the emulsified explosive. As the explosive spacing increases, the distance that the jet penetrates the explosive during detonation also gradually increases. When the explosive spacing exceeds 90 cm, the jet fails to initiate the explosive charge. (3) Field tests were conducted based on the tunnel blasting project of the Chengping Expressway (Beijing section) with explosive spacings of 50 cm and 70 cm. The test results revealed that better control of over-excavation and under-excavation was achieved at a spacing of 70 cm. Therefore, under the conditions of this project, a reasonable detonation distance is determined to be 70 cm. The findings of this study can provide valuable references for similar smooth blasting efforts in tunnel engineering.

This study investigates the blasting demolition of a 180 m-high reinforced concrete chimney under site-specific conditions, systematically addressing critical challenges in collapse control through targeted engineering solutions. By designing symmetrically arranged directional and positioning windows, combined with empirical formula calculations, optimal blasting parameters were determined to be a 216 central angle and a 3.5 m cut height, effectively guiding the chimney's collapse along the predetermined trajectory without significant backward displacement. A 1:1 scale numerical model employing the Interface Stress Element Method was developed to simulate the collapse process, showing complete structural failure within 14.0 seconds with controlled lateral deviation (<0.5%) and minimal settlement/forward surge. A comparative analysis with the Decoupled Co-node Model revealed the superior performance of the Interface Stress Element Method in simulating rebar-concrete decoupling at cut closures, reducing backward displacement by approximately 1.0 m through differentiated load-bearing mechanisms at material component nodes. The model successfully replicated restrained rebar scattering during top section ground impact, due to the bonding forces of the spring elements, confirming enhanced simulation accuracy in collapse kinematics. Field implementation validated the numerical predictions, achieving precise directional collapse, complete structural disintegration, and compliance with safety thresholds, thereby establishing a replicable framework for ultra-high chimney demolition engineering.

This study explored the influence of high-pressure gas blasting on coal's crack propagation and vibration characteristics. Using independently developed high-pressure air blasting devices, the high-pressure air blasting experiments were carried out on the simulated coal specimens. The surface crack propagation speed and particle vibration of the specimen were measured using a blasting speed acquisition instrument and a blasting vibration acquisition instrument, respectively. Furthermore, the crack propagation and fracture induced by high-pressure air blasting and the variation characteristics of particle vibration energy were analyzed. Scanning electron microscopy (SEM) was used to examine the evolution of pore cracks in specimens before and after blasting. The experimental results indicate that the surface cracks on the specimen are induced to develop and propagate along the direction of confining pressure loading at a design pressure of 15 MPa, and the crack development and propagation speed is v_{Bi-directional unequal pressure} > v_{no confining pressure} > v_{Bi-directional equal pressure}. Besides, The crack development and propagation speed vary under different confining pressure conditions, exhibiting two stages: rapid development and steady-state development as the distance from the crack initiation hole increases. The induced particle vibration signal is distributed in the range of 0~250 Hz, with the energy in the main frequency band of the vibration signal significantly different from that in other sub-bands and the vibration main frequency band significantly differing from other sub-bands. The primary vibration signal is concentrated in the low-frequency band of 0~31.25 Hz. These findings provide a theoretical basis and guidance for optimizing the distribution of fractures induced by high-pressure gas blasting and improving the effectiveness of gas extraction.

During drilling and blasting of open-pit mining in high and cold regions, water inrush or freezing often occurs on the borehole inside. This phenomenon creates a decoupled charge structure with water and ice, affecting the blasting effect and the rock-breaking mechanism under decoupled conditions. To determine the geometric parameters of the blasting crater and analyze the blasting effect under three types of decoupling medium in the high-cold area, a series of tests were conducted on the blasting effects of different decoupling charges in the Karma open-pit mining in Tibet. Based on the Livingston curve fitting results, the blasting parameters were optimized and applied to on-site engineering blasting. The results indicated significant differences between the visible volumes of the blasting crater and the crushed funnel at burial depths of 1.09~1.49 m. However, these volumes resembled burial depths of 1.49~1.69 m. Compared to the air-deck decoupling, the peak particle velocities under water and ice decoupling were reduced by 25.33% and 11.24%, respectively. The critical charge depths varied among the three decoupling materials, with water decoupling having the most significant critical depth, ice decoupling charge, and air-deck decoupling having the shallowest. The charge weights required for water and ice decoupling and ice decoupling were 18.9% less than those for air-deck decoupling. In multi-hole bench blasting, the explosive factor for water and ice decoupling was reduced by 18.2% compared to air-deck decoupling, and the rate of large fragments decreased from 8.9% to 4.3%. This indicated that water and ice decoupling charges made the energy distribution of explosives more uniform.

With the rapid advancement of modern industry, the demand for high-performance materials has grown significantly. Titanium/duplex stainless steel composite plates, known for their exceptional corrosion resistance, demonstrate vast potential for diverse applications. In this study, a bimetallic composite plate comprising TP270C titanium alloy and SUS821L1 high-strength duplex stainless steel was fabricated using explosive welding. The microstructural characteristics of the composite plate interface were thoroughly investigated through metallographic microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Additionally, the welding quality was systematically evaluated. The results showed that the welded interface exhibited an intermediate structure between flat and wavy when the interface deposition energy was low. In contrast, the welded interface displayed a wavy structure at higher interface deposition energy. Element diffusion and grain refinement were observed in the regions adjacent to both interfaces. Complete recrystallization predominated in the welded interface, molten zone, and adiabatic shear band. Near the welded interface, titanium underwent partial recrystallization, while duplex stainless steel exhibited a combination of partial recrystallization and deformed grains. Localized thermal accumulation facilitated grain growth in the molten layer, whereas titanium particles encapsulated within the molten layer exhibited refined grain structures. Mechanical performance tests indicated that the sample with higher interface deposition energy achieved a 40.33% increase in shear strength and a 4.52% improvement in bending strength compared to the sample with lower interface deposition energy.

Accurate acquisition of blasting vibration signals is essential for analyzing the harmful effects of blasting operations. However, geological conditions, electromagnetic interference, and instrument errors can introduce significant high-frequency noise into the collected signals, leading to distortion and inaccurate data interpretation. To address this issue, a signal decomposition algorithm based on Ospley Optimization Algorithm (OOA) is proposed to optimize Variational Mode Decomposition (VMD). Multiscale Permutation Entropy (MPE) is also employed to construct a noise reduction model for tunnel blasting vibration signals. OOA is iteratively applied to determine the optimal VMD parameters (K & α) and obtain the intrinsic mode formula (IMF) using the maximum information coefficient as the fitness function. The MPE values of each decomposed signal are then used to identify the noise components, which are removed to reconstruct the denoised signal. This coupled algorithm was applied to analyze the blasting effects in Dashan Tunnel, Yunnan Province. The results demonstrate that the proposed optimization algorithm effectively decomposes the signal and eliminates noise without significantly affecting the low-frequency energy. The OOA-VMD denoising method's performance is superior to the complete ensemble empirical mode decomposition (CEEMD) and conventional VMD algorithm, thereby verifying its reliability.