Mechanisms of Fracture and Fragmentation by Explosive Loading

The research reported here involved a study to answer some fundamental questions on the mechanisms of rock fracture and fragmentation by explosive loading. The program was experimental and dealt with the dynamic event as a three dimensional problem. Specifically, small scale models were used to obtain dynamic behavior of the model materials by measuring strain, stress, and particle velocity during the explosive event. Dynamic photoelastic methods were used to obtain data on the fracture patterns, propagation speeds, and sequences involved in the process. The effects of small flaws, large joints and discontinuities, and explosive source geometry were studied. The findings are 1 At early times, shock wave effects promote fracture initiation, coalescence and branching in the matrix material. At later times, the explosive gas pressure causes the cracks to extend and fragments to form.