Modelling of “Leo” Slope Failure Using a Distinct-Element Modelling Approach
On May 2021, a slope failure called “Leo Failure” occurred at Bingham Canyon Mine, one of the world’s deepest open pit mine, for a total runout mass estimated at 21 MT. Extensive and comprehensive monitoring of the mine activities allowed to anticipate and record the event and prevent any labor or equipment damage.
A 3D Particle Flow Code (PFC) model is used to simulate the failure runout to better understand ore grades within the runout mass. The model aims at reproducing the failure runout, and providing further understanding of the failed material characteristics, including lithology, ore grades and trajectory and landing position of rock blocks.
Itasca implemented a 3D micromechanical model of the failure event. A coarse (275,000 particles, diameters between 2 to 4 meters) and a fine resolution model (2 200,000 particles, diameters between 1 to 2 meters) have been investigated.
A trial-and-error procedure was used to reproduce the complex, two-stages failure observed on site and best match site measurements of the post-failure runout surface, relative positions of the failure zones, position of benches, and trajectories and final positions of markers.
A geology block model was then output from the final state of the model and compared with previous predictions and an assay block model created on site from actual drilling and sampling operations.
Both the coarse and fine model were satisfactorily calibrated. No significant differences were noticeable between the two models, thus the computationally efficient coarse model can be used for production.
The PFC and the Ore Control block model shows almost no difference in tonnage. This reflects that the distribution of rock types in the PFC model is very similar to the actual rock types in the Ore Control block model.
The variance in Cu grade to the Ore Control block model is reduced in the PFC model compared to previous predictions. This means that the output of the PFC model is closer to the actual grade of the mined material. This demonstrates the ability of such modeling in better predicting grades in the runout mass compared to existing methods, which is of interest for designing and planning site operations.
Ergun et. al. (2022), Particle Flow Code modelling of slope failure called ‘Leo failure’ runout to be used in grade control of runout mass mining at Bingham Canyon Mine. Slope Stability 2022 (TBP).