Numerical investigation on impacts of blast-hole deviation on fragmentation

Purpose and goal:

Drilling and blasting is a common method for rock excavation in mining. The blast-hole deviation often leads to reduced recovery, unplanned dilution, re-drills and a slower blasting cycle. The project aims to investigate the impacts of blasthole deviation on fragmentation. The objectives of the project are to evaluate the blasting performance with blasthole deviation based on numerical modelling and develop a modelling-based assessment procedure for given blast-hole deviation patterns.

Expected results and effects:

Both experimental results and numerical results show the investigated hole-deviation case produces finer fragmentation compared to the reference case. The numerical results also show that for the cases that one single blasthole deviates in the borehole plane, the case with a large inclination angle gives finer fragmentation. For the case with one single blasthole with outward deviation, the fragmentation is fine.

According to the numerical results of the two-blasthole case, the blasthole deviation causes coarser fragmentation. Approach and implementation:

A procedure is developed to evaluate the blasting performance with blasthole deviation based on numerical modelling. The parameters of numerical models are calibrated based on small-scale experiments. A code is developed to identify fragments and calculate the fragment size. The mean fragment size is employed as an indicator to assess the fragmentation. Different blasthole deviation scenarios are investigated and evaluated based on the calibrated parameters and the developed code.