A new Method for Measuring Mode-I Dynamic Fracture Toughness of Rock under Blasting Loads

Blasting excavation method by using explosive is still widely applied in mining and quarrying, and therefore, rock dynamic fracture toughness under blasting loads is one of the most concerned subjects in rock dynamics. In this paper, blasting experiments by using detonators and cement mortar specimens with a mode-I crack were conducted. The crack initiation time was determined by the strain signal recorded by a signal conditioner. The pressure acting on the hole was obtained by the strains measured from the two strain gauges near the hole, and then the pressure was applied as the dynamic boundary condition of the hole in the subsequent numerical calculation by using ANSYS code. The crack tip open displacements were calculated and applied in the determination of crack tip dynamic intensity factors KI, and accordingly the curve of KI versus time was obtained. The dynamic toughness was determined according to the time of crack initiation.