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Under which conditions can a normally deflagrating explosive detonate?
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A coal miner loading a drill hole with a water gel explosive called Tovex.
While deflagrating explosives (often called low explosives) typically involve rapid burning rather than the supersonic shock waves characteristic of detonation, they can be induced to detonate under specific, extreme circumstances.
The primary conditions that can cause a normally deflagrating explosive to transition into a detonation include:
- High degree of confinement: When a deflagrating explosive is contained within a vessel, the rapid expansion of gases increases pressure significantly. If this pressure is sufficiently high, it can force the material to transition from burning to a violent, supersonic detonation.12
- Large quantities: Using a large mass of the explosive material increases the likelihood of a transition to detonation, as the scale of the reaction can overcome the typical limitations of deflagration.2
The transition generally occurs through the progressive acceleration of the reaction, often involving a shift from laminar to turbulent flow, which eventually generates a shock wave. The heat generated by the compression within this shock wave leads to self-ignition of the mixture, establishing the detonation wave.3