Title: Impacts of Underground Mass Mining on Surface: Lessons Learned from the Palabora Cave-Pit Interaction Study
Distinguished Speaker: Erik Eberhardt, P.Eng., Associate Professor of Geological Engineering, Department of Earth and Ocean Sciences, University of British Columbia
Abstract: Although the economic benefits of block caving are appealing, the mass extraction of ore inevitably causes significant ground deformations that may adversely impact sensitive infrastructure on surface, as well as the natural environment. To better manage this risk, sophisticated 3-D numerical models are being employed to help assess subsidence magnitudes and extent. However, simplifying assumptions regarding the complex rock mass interactions involved and variability associated with geological heterogeneity, results in model uncertainty and the need for models to be calibrated and constrained.
To address these challenges, a large multidisciplinary collaborative research program, the Canadian Block Caving Subsidence Study, was initiated between the University of British Columbia, Simon Fraser University, Rio Tinto, and MDA Geospatial Services. Experiences from this five-year study will be shared, focussing on the Palabora block cave mine in South Africa.
Shortly after breakthrough of the Palabora cave into the bottom of an older open pit, the unexpected failure of an 800-metre-high pit wall occurred disrupting mine operations, damaging surface infrastructure and creating a dilution problem. Investigations were subsequently carried out as part of the UBC-led study, focussing on the integration of field mapping, rock mass characterization, InSAR monitoring and advanced numerical modelling to explore and better understand the complex spatial and temporal relationships that develop between the undercut, block cave, open pit and ground movements.