Technical Papers

Considering the Ice Excavation Required to Establish and Maintain an Open Ice Pit

Abstract

Several factors are increasing the likelihood of open ice pit mining adjacent to the Greenland ice sheet. This study employs a fully transient one-dimensional (1D) (depth-averaged) ice flow model, which includes a first-order longitudinal stress gradient approximation, to estimate the ice excavation required to establish and maintain an open ice pit. An idealized open ice pit geometry and purely deformational flow are assumed. A Monte Carlo approach is used to quantify the cumulative uncertainty in total ice excavation resulting from four key parameters: (1) ice temperature, (2) ice thickness, (3) equilibrium line altitude, and (4) surface mass balance gradient. Two scenarios of ice pit slope (2H:1V and 3H:1V), excavation method (constant and progressively steepening slope), and surface ablation enhancement (+25 and +50%), are considered. Total ice excavation is more sensitive to parameters controlling deformational velocity (1 and 2) than parameters controlling surface mass balance (3 and 4). Enhancing surface ablation by a feasible amount offers the potential to decrease total ice excavation by 10% over mine life. Progressively steepening the ice pit slope offers the potential to limit variability in ice excavation rate, and reduce velocity and ice thickness gradients conducive to crevasse formation.