Mechanics of deep underground explosions

Abstract

Discussion of the effects of explosions in soils is complicated by many factors, foremost among which are the physical characteristics of natural soils. In this paper, certain aspects of the mechanics of deep underground chemical explosions are treated theoretically in terms of a model of the physical situation. This model refers to the dynamic expansion of a spherical cavity in a plastic-elastic, incompressible, ideal soil of infinite extent, and it is analogous to one which has been used in studies of underwater explosions. The main predictions of the model studied are as follows. In all cases of practical interest, the expansion of the cavity is large and occurs rapidly, with an extensive region of the surrounding soil undergoing plastic deformation. The amplitudes of any subsequent pulsations are small. The features of the disturbance show much dependence upon the type of soil and upon the depth at which the explosion takes place. The present model seems to provide an acceptable account of some of the qualitative features of cavity formation due to a deep underground explosion. Furthermore, some quantitative agreement is found between predicted and observed sizes of cavities in one special case.