Study on the dynamic fracture law of layered materials under the explosive load of slotted charge

Abstract

Directional fracture blasting with slotted charge is one of the main rock breaking methods for excavating layered rock mass tunnels. This article uses dynamic photoelastic method combined with high-speed photography technology to visualize the process of explosive stress waves and explosive cracks passing through vertical layers of different strengths caused by the explosion of slotted charge. The dynamic fracture law of layered materials with different strength layers under slotted charge explosion loads was studied. The results indicate that the greater the strength of the bedding plane, the more significant the waveform changes of the explosive stress wave when transmitted through the bedding plane. When the strength of the bedding is relatively high, the crack velocity is less affected by the bedding. When the strength of the bedding is weak and there is a significant difference from the strength of the specimen material, the velocity of the crack after passing through the bedding will undergo severe oscillations. Before the main crack reaches the bedding plane and after passing through it, the fracture mode of the crack is mainly mode-I. During the process of the crack passing through the bedding plane, the dynamic crack transforms from the mode-I crack to the mixed mode crack. Under the premise of a certain crack velocity, bedding angle, and physical and mechanical parameters of the specimen, the propagation trajectory of the crack passing through the bedding is related to the difference in bedding strength and specimen strength.