Calibration analyses for production drift behavior at Chuquicamata underground mine

Authors: Alvarez, C; Gómez, P; Barindelli, G; López, S Download Paper

Cite As:
Alvarez, C, Gómez, P, Barindelli, G & López, S 2024, 'Calibration analyses for production drift behavior at Chuquicamata underground mine', in Daniel Johansson & Håkan Schunnesson (eds), MassMin 2024: Proceedings of the International Conference & Exhibition on Mass Mining, Luleå University of Technology, Luleå, pp. 1394-1405.



Abstract:
Chuquicamata Underground Mine (known to CODELCO as the MCHS project) started production in May of 2019 by undercutting the central macroblock (MB) of the first Lift, which is located approximately 200 m below the Chuquicamata Open Pit floor. However, stability issues started occurring in the production drifts by mid-2020, affecting the drift support systems to varying extents, including instances of collapse. Beginning in February 2020, the damage experienced by the support system was recorded monthly in terms of three categories defined by visual inspections as mild, moderate, and severe. This experiential data was used to calibrate a numerical model developed for the production level during undercutting. The numerical model, implemented in FLAC3D, included an advanced strain softening model, capable of simulating rock mass damage induced by abutment stresses from the advancing mining front. Damage assessment around the tunnels was based on emerging model parameters, such as deformations, which were then correlated to the observed damage categories. The calibration process focused on adjusting the softening model parameters, particularly critical deformation, to achieve a satisfactory alignment between model predictions and support observations, considering both the location and severity of damage. The model considered monthly intervals throughout the undercutting period (spanning 2 years), resulting in a reasonable comparison with actual drift performance. Special attention was given to the model's ability to replicate the deteriorating conditions observed in the drifts following the cave breakout on the pit surface.