Numerical simulation of rock fracture characteristics under combined action of impact and splitting

In this paper, a discontinuous rock breaking method under combined action of impact and splitting is presented. A dynamic model of rock splitting was established to study the fracture law of rock under impact pressure, with granite as the medium. Firstly, a numerical simulation of the rock splitting under static pressure was conducted. The applicability of the dynamic model was verified by comparison with the experimental results. On this basis, the numerical simulations of rock impact splitting with single frequency and multi frequency were carried out by different loading modes. The stress and damage, crack, splitting force and element failure were analyzed by comparing with static pressure splitting, and the “failure abrupt point”, which can be used as a direct evaluation index of rock impact splitting effect, was proposed. The results indicate that the rock can be completely broken only when the loading pressure reaches 3 MPa in the case of static pressure, while just 1.8 MPa for impact splitting. The required pressure of rock breaking by impact splitting is 60% of that by static pressure splitting, which greatly reduces the requirement on pressure. For single frequency impact splitting, frequency 35 Hz and 25 Hz have the best rock breaking effect, and 40 Hz has a better cracking effect. For multi frequency, the alternating frequency of 30 Hz and 40 Hz has the best effect.