The effect of physical structure changes of emulsion explosives on explosive properties under sub-atmospheric pressure environments

The high-altitude low-pressure environment significantly affects the explosion performance of emulsion explosives, yet the underlying mechanism remains unclear. To address this, this study systematically investigates the influence of low-pressure conditions on the explosion behavior of emulsion explosives, aiming to reveal the mechanism by which plateau environments affect detonation characteristics. The results show that within the pressure range of 68–100 kPa, the density of the emulsion explosive remains largely unchanged, but noticeable structural changes occur in the sensitized bubbles. When the pressure drops below 68 kPa, the density of the explosive begins to decrease, and effective bubbles gradually become ineffective. Correspondingly, the detonation velocity initially increases and then decreases with decreasing ambient pressure, peaking at 80 kPa—where it is 3.4% higher than that at 100 kPa. Numerical simulations of lead cylinder compression show a consistent trend with the detonation velocity: the maximum compression occurs at 80 kPa, and as pressure further decreases, the compression value gradually reduces from 12.09 to 9.66 mm, while the deformation timeline remains stable (compression phase ∼400 μs; tensile phase ∼200 μs). Further analysis indicates that detonation velocity is the dominant factor influencing lead cylinder compression, with structural effects being secondary. Specifically, within the 68–100 kPa range, microbubble activity promotes the formation of effective “hot spots,” leading to increased detonation velocity. Below 68 kPa, reduced density and the collapse or escape of effective bubbles result in fewer hot spots and lower detonation velocity. This study provides a theoretical basis for understanding the variation in performance of emulsion explosives in high-altitude environments.