Possible fracture criterion for the dynamic tensile strength of rock

An attempt is made to shed some light on the mechanisms of scabbing, spalling or slabbing by stress waves created by explosives or impacts. The dynamic tensile strength behavior under various stress waves is examined. The primary objective is to present the critical normal fracture strain energy theory and suggest its potential for some rocks. Also, it is pointed out that the dynamic tensile strength of rock and concrete (a pseudo rock) is not constant and varies with straining rate. Generally, the significance of the slabbing problem has been examined, and it's relation to dynamic tensile strength has been pointed out. The significance of the basic critical fracture strain energy is discussed, and its application to concrete is shown. Some work with quartz monzonite rock is presented. Recommendations are made for the potential application to and extension of the slabbing problem. A theory is propounded to explain dynamic tensile strength behavior, tests having verified the theory in the laboratory. The theory is extrapolated from concretes to a specific rock. (12 refs.)