Distribution of Cracks in an Anchored Cavern Under Blast Load Based on Cohesive Elements

Abstract

To explore the distribution of cracks in anchored caverns under the blast load, cohesive elements with zero thickness were employed to simulate crack propagation through numerical analysis based on a similar model test. Furthermore, the crack propagation process in anchored caverns under top explosion was analysed and the distribution and mode of propagation of cracks in anchored caverns when a fracture with different dip angles was present in the vault were discussed. With the propagation of the explosive stress waves, cracks successively occur at the boundary of the anchored zone of the vault, arch foot, and floor of the anchored caverns. Tensile cracks are preliminarily found in rocks surrounding the caverns. In the case that a pre-fabricated fracture is present in the upper part of the vault, the number of cracks at the boundary of the anchored zone of the vault decreases, then increases with increasing dip angle of the pre-fabricated fracture. The fewest cracks at the boundary of the anchored zone occur if the dip angle of the pre-fabricated fracture is 45º. The wing cracks deflected to the vault are formed at the tip of the pre-fabricated fracture, around which tensile and shear cracks are synchronously present. Under top explosion, both the peak displacement and peak particle velocity in surrounding rocks of anchored caverns reach their maximum values at the vault, successively followed by the side wall and the floor. In addition, they show asymmetry with the difference of the dip angle of the pre-fabricated fracture; the vault displacement of anchored caverns is mainly attributed to the formation of tensile cracks at the boundary of the anchored zone generated due to tensile waves reflected from the free face of the vault. When a fracture is present in the vault, the peak displacement of the vault decreases while the residual displacement increases.