Characterizing brittle fracture induced rockfall in an open sub-level retreat excavation

In this study, terrestrial LiDAR is used to characterize the contribution of rock bridge fracturing and brittle damage to rockfall on the contact wall of an open-air glory hole at Diavik Diamond Mine. Rockfall scars are identified and isolated by comparing successive LiDAR point clouds. Rock bridges are first characterized visually using 2D photographic trace mapping, and categorized as either coplanar with existing discontinuities or non-coplanar. Using an automated facet detection technique, and comparing the results to known mapped structures, we estimate the proportion of non-coplanar rock bridge fracturing contributing to rockfalls of various sizes. Roughness is used as an indicator of coplanar rock bridge fracturing, and roughness thresholds are estimated by comparing areas of highest roughness to damage trace maps. Finally, intact rock bridge estimates are used in a time-dependent degradation UDEC model to simulate progressive damage over the life of the mine. Modelling results show similar behavior to measured slope displacements, showing the importance of accounting for progressive intact rock fracturing over time.