The Use of FLAC Software for Assessing Deformation Rates during Ice Excavation for Open Pit Mining in Glaciers

Resource developments in glacial environments are becoming increasingly attractive as currently glacier-covered mineral deposits become exposed, easier to access and more economical to develop. Some mining projects are proposing to excavate large volumes of glacier ice to develop an open pit. Mining into an ice mass is challenging and needs to address the complex interaction of the glacier with pit excavation. Estimations of ice creep movements towards the pit are required to assess operational efforts and mine economics. In this paper the application of the finite difference computer software FLAC in estimating glacier ice deformation rates adjacent to a proposed open pit mine is presented. It is shown that the movement of glacier ice can be adequately modelled with a creep power law constitutive model (Glen's flow law) for ice. However, measured glacier movements are required to properly calibrate the constitutive model parameters. The calibrated model is then used to project glacier movements during ice pit expansion and to assess the stability of the excavated glacier ice face considering different excavation scenarios such as excavation slope angles and stages. The assessment shows that 2D numerical modelling is capable of providing useful insight into potential glacier movement mechanisms and changes in ice deformation rates. It can be a useful tool for planning safe excavation of the glacier ice.