Fracturing Behavior and Failure in Hollowed Granite Rock with Static Compression and Coupled Static–Dynamic Loads

Abstract

Underground excavation is often observed to be cut by induced fractures and, occasionally, collapses violently with the generation of a shear fracture throughout the opening. To study the development of these and other fractures seen around the cavity, cubes of granite rock containing a square opening with different dip angles were prepared and subjected to uniaxial compression and coupled static–dynamic loading. The results indicated that the dynamic crack initiation stress, the failure modes, and the dynamic crack velocity are associated with the prestress level when the specimen is under otherwise identical dynamic loading. With the increase of the prestress, the initiation stress first increases and then decreases sharply for the specimen with a ° dipping square opening, whereas it keeps decreasing monotonically for the specimens with 3° and 6° dipping square openings. The prestress has an obvious influence on the propagation velocity of the primary tensile crack, i.e., the primary crack velocity is reduced as the prestress level increases.