Referenced 3D images from inside cavities and behind rings in sublevel caving

Disturbance free fragmentation and flow in sublevel caving (SLC) are desirable as they could lead to an increase in ore recovery and a decrease in waste rock loading and nitrates leakage. This requires a reasonable understanding of the actual rock breakage in semi-confined ring blasting situations, where both the blasted geometry and the breakage itself are hidden. Sometimes there is a chance to inspect the actual conditions, such as in the opening of a new drawpoint and in hang-ups in which cavities exist. For these situations a lightweight mobile camera crane has been constructed for use in the LKAB Kiruna mine. A 3D photogrammetry system has been constructed, which enables the reconstruction of the ring front/cavity as a geo-referenced mesh model with color information. It is remotely operated from a safe distance behind in the drift. The paper first reviews the current drill and blast practice. Then it presents the design, construction and application of the 3D image acquisition system. A case study showsthe measurement application and also the evaluation possibilities. So far the system promises to be a valuable tool in increasing the understanding of SLC breakage and flow.