Fracture toughness weakening effect of high static pre-loaded CSTBD granite subjected to low frequency dynamic disturbance during the rock fracture

Abstract

Highly static pre-loaded rock with cracks will be generated during the deep rock engineering excavation, is subjected to low-frequency dynamic disturbance (Fd) to induce fracture failure. To investigate the fracture mechanisms of the high static pre-loaded rock with cracks, subjected to low-frequency dynamic disturbances, several tests were conducted on cracked straight through Brazilian disc (CSTBD) granite specimens using the MTS system. Based on the average static peak fracture load (Fmax) of the CSTBD specimens, three high static pre-load levels, Fp (70%, 80%, and 90% of Fmax), and the corresponding disturbance amplitude, Fa (30%, 20%, and 10% of Fmax), and low-frequency disturbance frequency, f (1, 5, 10, 30, and 50 Hz), were determined. The results revealed that the fracture toughness of the static pre-loaded CSTBD specimens subjected to low-frequency dynamic disturbance was lower than that under static load. The higher the Fp, the more significant is the decrease in fracture toughness with f. Comprehensive analysis indicates that the degree of fracture toughness weakening is highly dependent on the Fp, Fd induces strength weakening, and f affects the weakening degree.