The Formation of a Crater as Observed in a Series of Laboratory-Scale Cratering Experiments

A qualitative description of the formation of a crater is developed on the basis of a series of laboratory-scale cratering experiments. The results of 41 one-pound, single-charge cratering detonations in a concrete sand placed under controlled conditions are summarized. The effect of depth of burst on crater dimensions is illustrated. The crater formed by a one-pound charge buried at a depth of burst of 2 feet is selected for analysis because the ratio of depth of burst to depth of apparent crater is similar to that considered desirable for a prototype nuclear excavation. On the basis of these experiments and a series of gram-size, half-space cratering experiments conducted behind a Plexiglas plate, a description of the formation of a crater is hypothesized. Subsidence or slumping of the cavity walls during the formation of the crater is shown to play an important part in the formational process. The importance of this mechanism to the analysis of crater stability is discussed.