Numerical study on crack propagation of rock mass using the time sequence controlled and notched blasting method

In order to solve the directional fracture controlled problem of blasting construction in key parts or specific areas of some projects, two refined directional blasting methods, namely, time sequence controlled (TSC) blasting and notched blasting, are innovatively combined, and numerical comparison research of three kinds of compound blasting methods has been carried out. The results indicate that, for TSC blasting, the optimum delayed denotation time is a certain period of time when the explosive stress wave of the earlier detonated blasthole (EDB) propagates to the wall of the later detonated blasthole (LDB) that away from the EDB. In the TSC-notched blasting with four blastholes as a group, when the LDB and EDB is notched separately, the corresponding directional fracture length is 33.3 d and 45.2 d (d is the blasthole diameter), and the directional fracture length is 52.4 d as the blastholes are all notched. If it is needed to consider both the crack propagation effect and the construction costs, we suggest that the TSC-notched blasting with the notched EDB and the round LDB should be carried out, by which the quality of the profile could be ensured with a low construction cost.