Model experiments on crack propagation between two charge holes in blasting

Model experiments using PMMA plates and electric detonators were carried out to observe the dynamic fracture process between two charge holes in blasting by means of high-speed videography. The experiments are related with control of fracture planes along the line connecting the charge holes in smooth blasting. In this paper, firstly, the influence of the initiation time lag on the fracture formation between two charge holes was discussed. Secondary, the effect of a guide hole on fracture control was examined. The experimental results showed that the effect of stress reinforcement exists by simultaneously firing two charges. Applicability of the guide hole method using the circular hole having two notches for fracture plane control between two charge holes was demonstrated. The fracture process near the guide hole with two notches was also analyzed by numerical calculations using the dynamic finite element method.