To investigate the effect of boron nitride (BN) content on the explosion performance of on-site mixed emulsion explosives, the microstructure of BN-containing on-site mixed emulsion explosives were characterized by transmission electron microscopy and optical microscopy, and the thermal sensitivity, shock wave parameters, detonation velocity, and brisance of explosives were measured through steel plate tests, air explosion tests, the probe method, and lead cylinder compression tests. Combined with theoretical calculations, the influence of BN content on the microstructure, thermal sensitivity, and explosion performance of explosives was systematically studied. The test results indicate that the addition of BN does not significantly affect the stability of the internal phase droplets. At 240 ℃, the explosion delay time of the explosive samples increased from 114.28 s (blank sample) to 173.95 s (1.2% h-BN). As the mass fraction of BN increased from 0 to 1.6%, the detonation velocity, brisance, peak overpressure and specific impulse exhibited a trend of increase followed by decrease. The detonation velocity increased from 3850.45 m/s to 4724.89 m/s, and then decreased to 3903.20 m/s, with a maximum increase of 22.71%; the brisance first increased from 13.86 mm to 19.87 mm, and then decreased to 17.18 mm, with a maximum increase of 43.36%; the peak overpressure increased from 136.44 kPa to 318.33 kPa, and then decreased to 285.41 kPa, with a maximum increase of 133.31%; the specific impulse increased from 9.23 Pa·s to 33.98 Pa·s, and then decreased to 31.99 Pa·s, with a maximum increase of 268.15%. The study demonstrates that the incorporation of an appropriate amount of BN can significantly enhance the explosion performance of site-mixed emulsion explosives.

Silicon nitride, with high nitrogen content, was added to improve the explosive performance of bulk emulsion explosive. The influence of silicon nitride content on the air shock wave parameters, detonation velocity, and brisance was investigated by air blast experiments, detonation velocity tests, and lead column compression experiments. The results showed that: with the silicon nitride mass fraction increasing from 0% to 1.2%, the density of the explosive increased from 1.02 g/cm³ to 1.11 g/cm³, the air shock wave pressure peak increased from 0.1156 MPa to 0.2977 MPa and then decreased to 0.2408 MPa, with the maximum peak value being 2.58 times that of the minimum. The specific impulse increased from 9.22 Pa·s to 23.00 Pa·s and then decreased to 19.59 Pa·s, with the maximum specific impulse being 2.49 times that of the minimum value. The detonation velocity showed a trend of decreasing to 3265.66 m/s, then increasing to 4830.60 m/s, and finally decreasing to 4541.51 m/s, with the maximum detonation velocity being 1.48 times that of the minimum. The brisance increased from 13.86 mm to 19.40 mm and then decreased to 17.18 mm, with the maximum brisance being 1.40 times that of the minimum. From the experimental results, it can be concluded that silicon nitride can improve the explosive performance of bulk emulsion explosives, which is of reference significance for the optimal design of bulk emulsion explosives formulations.

The defective cracks were prefabricated on the wall of the notch holes by using polymethyl methacrylate (PMMA) material, which were parallel or vertical to the notch, and the distance from the defective cracks to the hole center was 2, 3, and 4 mm. The influence of notch hole wall defects on the crack propagation of notch blasting was investigated by using a digital dynamic caustic experimental system with numerical simulation. At the same time, triacetone triperoxide (TATP) explosives were employed as a charge, which served to mitigate the effect of gun smoke on the dynamic caustic experimental system and to improve the experimental design. The results demonstrate that the reflection of the stress wave at parallel defects results in a downward shift in the direction of crack initiation at the notch, but the refraction of the stress wave at vertical defects has no effect on the direction of crack initiation. The presence of wall defects in the hole impedes the impact of stress waves and blast gases on the cracks at the notch, resulting in a reduction in the length, expansion rate, and strength factor values of the cracks, and the degree of inhibition is contingent upon the distance of the defects from the centre of the borehole. As the distance between the parallel defects and the centre of the borehole increases, the inhibition effect of the parallel defects on both sides of the notch cracks gradually decreases. The inhibition effect of vertical defects on the far side of the notch cracks gradually decreases, while the inhibition effect on the proximal side of the notch cracks gradually enhances. The left and right notch cracks of vertical defects are more significantly affected by the boundary reflected stress wave than those of parallel defects. The notch cracks on the left side do not exhibit a clear pattern, owing to the pre-existing reflected stress wave at the defects. In contrast, the notch cracks on the right side are substantially diminished by the boundary-reflected stress wave as the vertical defects move away from the centers of the notch holes.