Bulletin 69—Lined-cavity shaped charges and their use in rock and earth minerals

By C. F. Austin, 1959, 80 pp, 6 tables, 48 figs., 1 plate, 1 index.

In recent years the attention of mining engineers has been focused occasionally on lined-cavity shaped explosive charges, often called shaped charges, cone bombs, and Munroe charges. At times, especially following WW II, various mining companies and explosives manufacturers have carried out investigations of the use of lined-cavity shaped charges in the mining industry. Most of these projects received little publicity and generally were considered failures in so far as the development of commercially useful applications was concerned.

In view of spectacular military successes with shaped charges, the general lack of success in the development of commercial uses suggests that perhaps the commercial investigations tended to overlook some essential factor in the design of the shaped charges utilized. From what can be determined concerning most of the projects that failed, this was indeed the case.

Two factors appear to have been the source of the disappointments experienced. The first of these lay in the field of applications. Most work was done with the idea of using the lined-cavity charge by itself as a secondary blasting tool; yet the lined-cavity charge is best suited for punching a hole into a target, not for breaking it. The second and most serious difficulty lay in the type of explosive used. Ordinary, low-velocity, low-brisance mining explosives cannot yield a workable lined-cavity shaped charge. Unfortunately, high-velocity, high-brisance explosives are difficult to obtain. The lack of proper explosives, coupled with the fact that relatively little is known of lined-cavity phenomena outside of ordance circles, meant that many of the early investigations failed to achieve workable shaped charges.

The purpose of this bulletin is to demonstrate that properly constructed lined-cavity shaped charges can yield penetrations that are of value in mining and allied industries. The treatment includes a general discussion of theory and a detailed discussion of charge performance in various target types.