Numerical study of presplit blasting in rock masses with a closed and filled joint using coupled finite-discrete element method

Abstract

The optimized performance of rock blasting heavily relies on the presence of discontinuities. These geological features play an important role in wave and fracture propagation in rocks and can be considered a barrier against the blast wave and fracture propagation. Blasting has many applications, but one of the important aspects is presplitting blasting, in which light blasts are operated to create a continuous plane prior to the main blasting. The goal of this particular blast operation is mainly to inhibit damage to the reserved rock. In the presplit blastingin underground rocks, the magnitude of the ground in-situ stresses plays a vital role and dominates the performance of the presplitting, which can lead to an unsuccessful detonation if mismeasured. There is much evidence that, in many cases, the joints are not closed but instead are filled with a different material. Thus, in this study, the performance of presplit blasting in a rock domain with a closed or filled joint is analysed using the combined finite-discrete element method (FDEM) with a gas in fracture logic. First, the applicability of the method is verified against some experiments. Once verified, 2D FDEM models are analysed to evaluate the influence of an inclined closed or filled flaw on blast-induced fracture development. The FDEM results confirm the strong impact of joint inclination angle on the fragmentation degree. Furthermore, it is shown that the performance of the presplit blasting is remarkably dependent on the magnitude of ground in-situ stresses. The results also show that the filling material and its orientation angle with respect to the maximum principal stress have an imposing effect on the success of the presplitting blasting. Also, it is revealed that in the presplit blasting with filled joint, the failure of the filling is a mode failure, while the connecting fractures are of tensile mode.