Block geometry and rockmass characterization for prediction of dilution potential into sub-level cave mine voids

When sub-level caving is used as an underground mining method for the exploitation of diamondiferous kimberlite pipes, a deep, steep-sided pipe is created that is susceptible to sloughage. Pipe wall sloughage allows waste rock to mix with and dilute the caved kimberlite ore. Using the Koala Kimberlite Pipe at Ekati Diamond Mine as a case study, a method has been developed, using rockmass and rock structure characterization integrated with discrete block (DEM) simulation, for comparative assessment of dilution potential and the classification and mapping of dilution source zones around the kimberlite pipe. The assessment process involves the development of a geomechanical model to delineate the structural fabric within the host rockmass and characterize the size and shape distributions of discrete rock blocks defined by intersecting discontinuities. Combining the slope geometry with the structural geology model allows for a zone-by-zone numerical analysis of pipe wall stability under gravitational loading. A final dilution map is developed in order to target problem areas where the highest levels of slope instability are anticipated.