Project Background

In mid-2021, New Gold Inc. began production from the B3 panel at the New Afton Mine in British Columbia, Canada. The B3 panel is located approximately 160 meters below and west of the existing Lift 1 caves. To support effective cave propagation and breakthrough with Lift 1, various monitoring tools such as Time Domain Reflectometry (TDR) sensors, seismic recordings, and cave tracker beacons were implemented. In 2022, ITASCA calibrated advanced numerical models using the available monitoring data. The goal was to improve the understanding of rock mass behavior during cave initiation, propagation, and eventual breakthrough into Lift 1, and to inform key operational decisions related to safety and infrastructure planning.

Objectives

• Assess and predict the cave propagation behavior of the B3 cave and its interaction with Lift 1 infrastructure.
• Use real-time monitoring data to calibrate numerical models.
• Support operational decision-making to improve efficiency and safety, particularly the timing of tunnel abandonment, bulkhead installation, and the assessment of cave-to-cave interactions.

ITASCA’s Role

ITASCA Minneapolis focused on predicting and understanding the cave propagation dynamics of the B3 panel at New Afton Mine. The B3 panel, located 160 meters below the existing Lift 1 caves, introduced new operational challenges related to cave breakthrough timing and infrastructure safety. To address these challenges, a coupled FLAC3D-MassFlow modeling approach was used in combination with the ITASCA Model for Advanced Strain Softening (IMASS). This approach simulated the progressive failure and movement of rock masses while accounting for material flow within the cave. The model was calibrated using real-time field data from Time Domain Reflectometry (TDR), seismic monitoring, and Elexon cave tracker beacons. The resulting model provided predictions of cave initiation, propagation, and interaction with Lift 1 infrastructure, guiding key operational decisions like tunnel abandonment and bulkhead installation.

Featured ITASCA Software

FLAC3D

MassFlow

Project Results

Calibration of the B3 Cave at New Afton Mine compared the cave initiation and propagation to TDR breakage data, beacon smart markers movement, and seismic tomography interpretations. The fault strength was downgraded to match cave-scale observations, which is aligned with the inherent bias on UCS testing for weak material, where the core recovery is usually low and only the best portion of the core is tested. The use of IMASS and the coupled FLAC3D-MassFlow approach allowed calibration of the model against different monitoring instruments in terms of fracture and mobilized limits.

The calibrated model was used to predict the breakthrough timing of the B3 Cave with respect to the mobilized limit of the West Cave, the Lift 1 drifts, and the haulage and vent levels underneath Lift 1, which helped manage the timing of bulkhead installation and definition of safety distances in the active drifts in Lift 1 to ensure worker safety and minimize operational disruption. In a separate study, the calibrated model was used to assess the footprint stability of the B3 panel.

References

• Cancino, C., Fuenzalida, M., & Kamp, C. (2024). Numerical modeling of cave propagation and breakthrough timing: A back-analysis at New Afton mine. MassMin 2024 (Proceedings, International Conference & Exhibition on Mass Mining, Kiruna, Sweden, September 2024), 548–565.