Abstract

The Chuquicamata Underground Mining Project (PMCHS) is one of the world's most challenging and important caving projects, as it requires the transition from one of the largest open pit mines in the world to a large-scale underground operation. In caving operations, the construction of drawbells is critical for production as these are the openings through which caved ore is extracted. The literature indicates there is no definitive blasting design methodology for drawbells when excavation is required to be completed in one phase, despite the importance and frequency of this type of requirement. Thus, during the implementation stage of the PMCHS, it was relevant to carry out an experimental programme to first design a methodology based on rock mass blasting parameters, and then conduct controlled industrial experiments to test the design's efficiency and re-engineer it accordingly. The blast design is based on the estimation of peak particle velocity (PPV) and associated damage per blast-hole. The blast sequence was defined from elemental wave analysis. Measurements during the experimental programme included drill deviation, explosive density during loading, and velocity of detonation (VOD). Drawbell geometry in one phase was successfully implemented when more than 80% of the area of the drawbell design was over four times the critical particle peak velocity (PPVc). The results obained from measurements of fragmentation and overbreak in pillars and brow during test 1 were used to improve the blasting design for test 2 so that both time and cost were reduced.