To address the absence of specialized explosives for mine presplitting blasting and excessive detonation velocity/power of conventional 32 mm emulsion explosives, this study proposed reducing the explosive diameter to moderate detonation characteristics. By combining critical diameter theory with numerical simulation analysis, a PVC tube charge model was developed in LS-DYNA. The detonation wave propagation was simulated using ignition-growth reaction-rate equations and fluid-solid coupling algorithms, with detonation-curve analysis verifying explosive stability. The BSS-1 intelligent ten-stage detonation velocity meter was employed to measure detonation velocities of emulsion explosives of different diameters, thereby enabling the determination of their critical diameter from experimental data. Results demonstrate strong agreement between simulations and experiments: stable detonation occurs at 14 mm diameter, while failure occurs at 12 mm, establishing the critical diameter range as 12 ~ 14 mm. Additionally, when the diameter exceeds 14 mm, the detonation velocity exhibits a positive correlation with diameter increase. This study, cross-validation of numerical simulations and field experiments, identifies the critical diameter range for industrial emulsion explosives in mining applications, offering empirical support for optimizing presplitting blasting parameters and enhancing safety management.

To address the technical challenge of blast-induced overbreak at tunnel crowns during soft rock roadway excavation, this study proposes an optimized presplit-smooth blasting synergistic method. Theoretical analysis grounded in wave impedance principles demonstrates that the wave impedance disparity between pre-split cracks and surrounding rock creates a high-reflectivity interface, fundamentally altering stress wave propagation dynamics. When the stress wave reaches this interface, most of its energy is reflected, with only a small portion transmitted, resulting in substantial attenuation of wave intensity. This phenomenon transforms the initially transient, intense impact energy into a millisecond-scale, gradually released load, effectively mitigating energy superposition from subsequent stress waves and preventing cumulative damage within the rock mass, thereby significantly improving the dynamic stability of the geological structure. Numerical simulation results demonstrate that the synergistic method outperforms conventional smooth blasting by effectively confining the damage zone within the presplit fracture boundary, resulting in a remarkable reduction in crown damage depth to 0.3 m. Furthermore, this approach substantially decreases peak particle velocity (PPV) while transforming the loading profile from a transient sharp-rise/slow-decay' impact to a more controlled millisecond-level delayed-release' pattern featuring gradual pressure buildup and deferred peak intensity. Field implementation of the optimized synergistic scheme in the kaolinized diorite porphyry roadway at the-350 m level of the Gushan Iron Mine demonstrated exceptional contour control, maintaining intact surrounding rock in weak interlayer zones without spalling or collapse. The study verifies that the presplit-smooth blasting synergistic method, leveraging stress barrier effects and meticulous parameter optimization, achieves a substantial reduction in blast-induced damage and vibration while effectively mitigating overbreak in soft rock roadway excavation.

Weak interlayers can easily lead to problems such as over-excavation, under-excavation and low semi-porosity in slope pre-split blasting, and it is critical to clarify the influence of its angle on the blasting effect to optimize the blasting parameters. In this paper, the numerical simulation method is employed to systematically investigate the mechanism of multiple weak interlayer angles on the pre-split blasting effect, utilizing the ANSYS/LS-DYNA finite element program as the technical platform. Based on the physical properties of rock, joints, air and explosives, four types of material models were selected:the HJC concrete model simulated the rock, the PK bilinear follow-up hardening model represented the joints (weak interlayer), the ALE model represented the air, and the HEB model described the explosives. The non-reflection boundary condition is introduced to reduce the reflection interference of boundary stress waves, and the study is parameterized for quantitative analysis. A three-dimensional numerical model was constructed, including eight blast holes. The height of the bottom and upper benches was 200 cm and 1200 cm, respectively, and the slope angle was 80. When the grid is divided, the blast hole and the surrounding area are encrypted, and the global grid is 50cm long to balance the calculation efficiency and accuracy. The simulated conditions include a complete slope and some weak interlayer slopes with angles of 45° and 90° to the blast holes. The stress changes are tracked through the monitoring points (located at the middle and bottom of the model), and the stress wave propagation, pre-split formation process, and overbreak characteristics are analyzed. The final results show that the weak interlayer exacerbates stress concentration, and the overbreak is more severe at a 45° angle. Additionally, the pre-split flatness is poor, and the semi-porosity is low. At an angle of 90°, the degree of overbreak is relatively light. The barrier and energy absorption effects of the weak interlayer decrease with an increase in the angle and increase with an increase in the number.

In order to realize the blasting demolition of 62.8 m high brick structure chimney in complex environment, various demolition options which fully consider the structure of the chimney and the surrounding environment were compared in the case of insufficient space for collapse on the east, west and north sides. After analysis, one-way and two-way folding blasting options were initially selected to blast and demolish the chimney. The circular angle of the upper and lower notch was designed as 220°. The lower notch was set as 2 m high at 0.5 m from the bottom of the chimney, while 30 m from the bottom of the chimney located the upper notch which parameters need to be simulated and optimized. ANSYS/LS-DYNA finite element analysis software was used to compare the collapse effect of the preliminary scheme, and it was calculated that the one-way folding blasting did not meet the demolition requirements, so the two-way folding blasting was selected. Then the chimney collapse process was simulated with the upper cut height of 1m, 1.5 m and 2 m and the delay times of 0.5 s, 1 s, 1.5 s, 2 s and 2.5 s between the upper and the lower cut. After analyzing the collapse process and the distribution range of the blast pile of the chimney under different working conditions, it was determined that the best folding effect with a small collapse space happened when the upper cut height was 1m and the delay time was 1 s. Furthermore, safety measures which were related to blasting vibration and flyrock protection were designed. The blasting effect showed that the chimney collapsed smoothly according to the designed direction during the blasting process, and no damage occurred to the surrounding buildings(structures). The overall blasting demolition effect was good enough to meet the expected goal. It can provide a reference for related scholars and demolition projects.

To investigate the effects of decked charge structure on the energy transfer and blasting outcomes, a study was conducted to improve the energy utilization rate of explosives and enhance the blasting impact based on the blasting operations of a limestone mine in Chenzhou. Combining LS-DYNA numerical simulations with on-site optimization experiments, this research examined the rock stress distribution across different charge structures during bench blasting. Simulations were performed on four charge structures: continuous charge, 0.6 m deck, 1.0 m deck, and 1.5 m deck, with effective stress monitored at key points. Field optimization experiments were then conducted using a novel transmissible explosive deck to analyze the overall blasting performance of the blast pile. The research results indicate that the rock damage extent and average maximum effective stress reach peak values at a 1.0 m deck length, resulting in favorable fragmentation. In field tests, the decked charge reduced the powder factor from 0.199 kg/t to 0.179 kg/t, lowered the fine ore rate by 6.54%, reduced the oversize rate by 3.7%, and increased the average block size by 5 cm. This approach minimized energy wastage and resolved uneven fragmentation issues with mixed emulsion explosives, enhancing the mine′s economic efficiency.

With the widespread use of mixed emulsion explosives, there exists the situation that the stemming materials penetrate into emulsion explosives in open-pit blasting construction, which indirectly changes the stemming length and reduces the blasting effect. To study the influence of stemming on mixed emulsion explosives, stemming simulation tests, numerical simulation tests and field blasting tests were carried out successively. Firstly, four kinds of PVC pipes with common hole diameters were used to simulate the blasting holes, and the rock chips were used to simulate the stemming materials. They were used to systematically study the infiltration of rock chips into the explosives on top of the explosive column during the filling process of stemming. Secondly, the numerical simulations of single-hole blasting were conducted with the LS-DYNA software, and the influence of the stemming mixture at the top of the explosive column on the explosive power was investigated by observing the changes of stress values at the measurement points. Finally, the stemming filling process was improved by setting physical isolation during the charging process based on the bench blasting in the Jinduicheng open pit mine. And the effect of stemming on the mixed emulsion was analyzed by comparing the blasting effect before and after the physical isolation. The results show that the phenomenon of explosive overflow appears on the top of the explosive column in the explosive charging process. Then, the rock chips gradually infiltrate into the emulsion explosive due to the influence of gravity after the charging is completed, and the infiltration length of rock chips increases with the increase of hole diameter in the same time. The numerical simulation results show that the stresses of different monitoring points have decreased, and the infiltration of stemming reduces the explosive power of the top explosive. The fragmentation analysis of the top rock after improvements shows that the main fragment size distribution of rocks decreases from 20~40 cm to 0~20 cm, and the proportion of rocks over 60 cm decrease from 6.13% to 1.81%, compared with the conventional charging process. In summary, the stemming has a significant impact on the power of emulsion explosive and blasting effect, and it can effectively improve the blasting effect by taking physical isolation to separate the stemming and explosive.