Rock mass characterization and assessment of block-forming geological discontinuities during caving of primary copper ore at the El Teniente mine, Chile

The primary copper ore at the El Teniente mine is very competent and massive. It is a rock with almost no open discontinuities. Nevertheless, there is a high frequency network of small scale veins coupled with widely spaced faults. A research investigation was implemented to determine what discontinuities are the most relevant in the rock mass disassembly process during cave mining. Rock mass characterization was undertaken at four different scales within the rock mass, in particular the block-forming discontinuities were characterized by studying a significant number of blocks at the caving draw points. Two relevant discontinuity characteristics have been found. The data suggest that discontinuities having approximately less than 1/3 of hard minerals as infill and thicknesses greater than or equal to 2 mm are weaker and more likely to define blocks during caving and the subsequent comminution process. The infill characteristics have been used to characterize rock mass quality in different sectors, and the results are in accordance with actual observations at the mine site.