The surrounding rock during a coal mine excavation is prone to significant engineering disasters such as considerable deformation and rock bursts. Pressure release can improve the stress field of a deep rock mass and prevent the occurrence of dangers such as roadway collapse and coal and gas outbursts. This paper uses the ANSYS 19.0/LS-DYNA finite element software to simulate the crush area and fracture zone of a detonation charge with different diameters under in situ stress. The stability of the surrounding rock was analyzed based on the impact stress and velocity, and was verified by field tests. The research results show that the blasting load primarily affects the damaged area near the borehole, while the in situ stress affects far-field crack propagation. The crack propagates in the direction of high surrounding rock pressure. When the uncoupling index is 1.5, the impact pressure of a 60 mm diameter cartridge is eight times that of a 20 mm diameter cartridge. The impact speed can reach two times that of the 20 mm diameter cartridge. The high-energy event at the roof is transferred to the front of the working face, the distribution is no longer concentrated, and a better pressure-relief blasting effect is achieved. The research results can help guide the prevention and control measures of rock bursts and other mining disasters.

This study systematically analyzes the influence of the charge length-to-diameter ratio and stemming length on the radius and volume of blasting craters in coal and rock blasting crater tests to effectively address the challenge of achieving coal–rock separation in mixed blasting construction. In addition, it examines the energy distribution mechanism of blasting fragmentation and establishes characteristic equations for coal and rock blasting craters. Numerical simulations and blasting tests are conducted to investigate the casting effect of rock benches and the fragmentation characteristics of coal and rock benches under different charge structures. The results indicate that when the ratio of charge length to stemming length exceeds 0.91 and 0.74 for the coal and rock benches, respectively, the utilization rate of explosive energy for rock fragmentation gradually surpasses that for rock throwing. The charging structure is identified as a key factor in achieving coal–rock mixed blasting and separation mining. The explosive energy is effectively utilized with a bottom interval length of 2 m for rock benches and a stemming length ranging from 2.5 to 3 m for coal seams. This configuration raises the connectivity of rock damage cracks, improves the distribution of tensile cracks at the top of the coal seam, and prevents bulging or coal–rock interactions (blasting mixing) at the coal–rock interface. The findings demonstrate that the optimized charging structure effectively achieves separate mining in coal–rock mixed blasting, fulfilling the requirement of avoiding coal–rock mixing during blasting. The research provides valuable mining strategies and technical experience for achieving separate mining in coal–rock mixed blasting in open-pit coal mines and improving the recovery of thin coal seams.

The surrounding rock during the coal mine excavation is prone to significant engineering disasters such as considerable deformation and rockbursts. Pressure release can improve the stress field of a deep rock mass and prevent the occurrence of dangers such as roadway collapse and coal and gas outbursts. This paper uses the ANSYS/LS-DYNA finite element software to simulate the crush area and fracture zone of a detonation charge with different diameters under in-situ stress. The stability of the surrounding rock was analyzed based on the impact stress and velocity, and was verified by field tests. The research results show that the blasting load primarily affects the damaged area near the borehole, while the in-situ stress affects the far-field crack propagation. The crack propagates in the direction of high surrounding rock pressure. When the uncoupling index is 1.5, the impact pressure of the 60 mm diameter cartridge is 8 times that of the 20 mm diameter cartridge. The impact speed can reach 2 times that of the 20 mm diameter cartridge. The high-energy event of the roof is transferred to the front of the working face, the distribution is no longer concentrated, and a better blasting pressure relief effect is achieved. The research results can help guide the prevention and control measures of rock bursts and other mining disasters.

To investigate the dynamic response at the terminus of oblique intersecting joints subjected to stress waves, a comprehensive approach integrating theoretical derivation, numerical computation, and experimental validation was used. A hyperbolic constitutive model of joints was introduced. The propagation equation for stress waves impinging upon nonlinear oblique intersecting joints was derived based on the superposition principle. A mechanical model of J ₂ was constructed. The auxiliary function of δ function was selected as the incident wave. The calculation formula for stress and displacement at the terminus of oblique intersecting joints was derived using the Westergaard complex analytical function. Concurrently, cement mortar rock‐like samples with oblique intersecting joints were fabricated. It was found that the time‐history curves, the peak‐value laws, and the influencing characteristics of joint nonlinearity on σ _x and σ _y at the four feature points at the terminus of J ₂ are in good agreement with the results of experimental validation. The results indicated that the stress contour at the terminus of oblique intersecting joints forms a closed loop, suggesting that the stress increases as the distance to the joint terminus decreases. σ _x is prone to inducing tensile rupture in the 315° directions. At the same location at the terminus of J ₂ , the magnitude of σ _y is lower than that of σ _x . The stress contour of τ _xy with the same gradient forms two closed loops, resulting in doubling of the initiation positions of shear rupture. The displacement contour at the terminus of oblique intersecting joints shows a divergent pattern, suggesting that the displacement decreases as the distance to the joint terminus decreases. The displacement fields of u and v do not show a symmetrical distribution along the interface of J ₂ . The u displacement field undergoes a counterclockwise rotation around the right‐hand endpoint of J ₂ . The direction of zero displacement undergoes a significant change from 30° to 60°, leading to a change in the direction of shear crack propagation. The present study provides a foundational framework for analyzing the propagation characteristics of stress waves incident on naturally jointed rock masses. It facilitates investigations into the fracture mechanisms of naturally jointed rock masses subjected to stress waves.

The effects of MATE-ADV densifier dosage on CT-resolvable pore characteristics and compressive strength in fly ash–slag concrete remain insufficiently quantified. An L9 orthogonal array was used to evaluate cement content, sand ratio, fly ash (FA) content, and densifier dosage. X-ray computed tomography (X-CT) characterized the specimens at 28 d, and compressive strength was measured at 7, 14, and 28 d. Across the nine specimen groups, mean slice porosity ranged from 0.75% to 2.50%, while 28 d compressive strength ranged from 59.49 to 68.37 MPa. Exploratory pooled-error ANOVA suggested main effects of cement content (F_(2,4) = 8.05, p = 0.040) and sand ratio (F_(2,4) = 7.71, p = 0.042) on mean slice porosity. Cement content and sand ratio showed the largest main effects on 28 d strength; FA content was also significant, whereas densifier dosage was not (F_(2,18) = 2.79, p = 0.088). X-CT analysis showed variation in pore-section area and circularity among the groups. A second-order logarithmic model summarized the observed porosity–strength relationship (R² = 0.948; leave-one-group-out RMSE = 1.422 MPa). Finally, a candidate for the optimal mix proportion was identified by jointly considering the evaluated 2D pore characteristics and 28 d compressive strength.