In the practice of the geomechanical design of the extraction level of block caving mines, the spacing of drawpoints and production drifts is critical for life of mine footprint stability, gravitational flow, interaction of draw zone and reserve assumptions.
This paper consolidates the results of the geotechnical and gravitational flow evaluation carried out for the Macroblock S5 (MB S05) of the Chuquicamata underground mine (MCHS) to optimise its current design. In particular, four designs corresponding to the El Teniente layout with dimensions of 15 × 22 m (15 m along production drifts and 22 m between drawbells drifts), 15 × 24 m (15 m along production drifts and 24 m between drawbells drifts) and with variants of crown pillar of 20 and 22 m in height for each case have been analysed. Gravitational flow studies were carried out with empirical methods and through simulations using Geovia PCBC software. The marker mixing (MMIX) algorithm was also used, which allows for modelling and for the simulation of various forms of mixing during ore extraction.
The performance of each design was analysed considering an approach based on local numerical models through the integration of a high-resolution mesh generator and the finite difference program FLAC3D. From the analyses carried out, design options were studied in terms of Factor of Safety and stress-strain response
to the application of increasing loads on the pillars compared to the alternative designs. The selected design option was evaluated with an overall scale model incorporating the geotechnical model, geological faults, and excavation sequence of surface mining.
As part of this study, complex three-dimensional continuum models were developed and applied to evaluate the influence of the previously mentioned variables in the mechanical response of the underground workings, particularly, related to abutment stress developed in critical areas such as pillars and drawbells. This paper describes general and particular aspects of the MB S05, concentrating mainly on the rock mass behaviour of the operative MBs, using three-dimensional modelling.
