Camouflet

A camouflet, in military science, is an artificial cavern created by an explosion. If the explosion reaches the surface then it is called a crater.

The term originated in a countermine dug by defenders to defend against the undermining of a fortress's walls during a siege. The defenders would dig a tunnel under the attackers' tunnel. An explosive charge would be set off to create a camouflet that would collapse the attackers' tunnel.

More recently, the term has been used to describe the effects of very large bombs like the Grand Slam bomb, which are designed to penetrate next to a large target structure and create a camouflet to undermine the foundations of the structure. It has been observed that it is more efficient to penetrate ground next to the target than on target.

A camouflet set was used to describe a system used in the British Army for cratering tracks and other routes. A tube was driven into the ground using a manual post driver. The end of the tube was a disposable steel point. A small charge connected to a detonator was lowered down the tube. The tube was then removed, and the hole tamped. The charge was blown, leaving a void and a hole to the surface. This void was then filled with a much larger charge, which was also tamped, and then blown when required to create a crater as an obstacle. This was replaced in the 1980s by a system using a shaped charge to create the initial hole.

Because of the presence of high levels of toxic fumes from the explosive, including carbon monoxide, and the weakness of the soft earth overlying the cavern, camouflets are extremely hazardous to bomb disposal personnel.