Numerical study on the dynamic fragmentation of rock under cyclic blasting and different in-situ stresses

To study the dynamic fragmentation of deep-buried rock under cyclic blasting and different in-situ stresses, a series of theoretical analyses and numerical simulations were conducted. Firstly, the distribution of hoop stress around blasthole under static load was elucidated. Then, the parameters of Riedel-Hiermaier-Thomal (RHT) model were obtained by the experimental data of marble sample. Thirdly, numerical simulations were carried out on the damage evolution process of rock single blasthole cyclic blasting. Finally, the influence of initiation sequence and in-situ stress on tunnel excavation was discussed. In addition, the blasthole parameters were optimized based on the improved tensile and compressive strength criteria. The results show that the rock blasting crack tends to propagate along the direction of maximum principal stress. The newly added breakage rock elements caused by successive blasting of single blasthole gradually decreases. In tunnel presplit blasting, the interval blasting can improve the rock breaking effect and increase the degree of rock fragmentation. For the blasting excavation of deep-buried tunnel, the blasthole parameters obtained by the improved tensile and compressive strength criteria can ameliorate the under-excavation phenomenon caused by in-situ stress and enhance the blasting quality.