Influence of Slot Width in Cartridge on Crack Propagation and Energy Concentration Under Explosion Load

The demand for controlled blasting technology is increasing and the employment of slotted cartridges becomes prevalent. To investigate the influence of slot width on the patterns of crack expansion (crack refers to the sudden and violent fracture that occurs during blasting), five sets of model experiments were performed utilizing the dynamic caustics test system, with the slot width ranging from 0.50 to 1.50 mm. Upon this, numerical simulation was performed using the LS-DYNA finite element software to scrutinize the stress propagation process, and analyze the peak Von Mises stress at diverse monitoring points surrounding the borehole. It indicates that the angle (θ) of the primary crack at the slot is affected by the slot width (B), and their relationship agrees with an inverse tangent function. The angle (θ) gradually increases with the augmentation of the slot width (B). Furthermore, the average peaks of burst primary crack expansion velocity and dynamic stress intensity factor are affected by the slot width. The former experiences a reduction of 38%, while the latter undergoes a decline of 42% across the spectrum of slot width from 0.50 to 1.50 mm. The numerical simulation results indicate a close alignment between the crack expansion pattern and the observations from dynamic caustics experiments. The Von Mises stress primarily concentrates in the normal direction of the slot and at the tip of the crack. With the augmentation of slot width, the Von Mises stress at each monitoring point in the slot direction suddenly increase, and the time-course curve presents the more pronounced double peaks.