Destruction of Model Earthen Tunnels by Internal Explosive Detonation

Abstract

Abstract : The report describes a series of explosive demolition tests on small horizontal tunnels in soil using line charges of Primacord. The objectives of the tests were to study the mechanisms of failure of model tunnels in earth when subjected to internal explosions and to develop a means of predicting failure considering the soil properties (detailed in Appendix A) and tunnel geometry. A nondimensional approach to data analysis was proposed to account for the many test variables, including soil properties, geometry, and explosive loading density; although only a limited number of tests were performed, this method of approach appears to be valid. Results for the dominant test condition investigated (depth of cover H four times the tunnel diameter D) indicate that a minimum loading density of 0.3 lb/cubic feet of Primacord is required to destroy tunnels in a strong, cohesive soil. A dimensionless plot was constructed from the results of these tests. This plot includes only the condition H/D = 4; therefore, with this plot and a known tunnel size, the amount of Primacord to destroy a tunnel of H/D = 4 in various strength soils can be determined.