Cumba Slope Failure: A Technical Review 

Abstract

Slope failures are an inevitable aspect of economic pit slope design and execution in the mining industry. Industry standards typically accept up to 30% of benches in surface mines to collapse, provided that they are managed such that no personnel or critical infrastructure are at risk. For larger scale instability, the acceptable limits reduce to 5-10% and 3-5% for inter-ramp and overall pit slopes. Ground control measures in large surface mines typically include real time monitoring systems and comprehensive response protocols to prevent personnel and equipment being exposed to safety risks associated with slope failures. Economic risks are often managed with attempts to reduce slope design uncertainty with ongoing site investigations including drilling, mapping, photogrammetry and also the use of monitoring data. Our ability to collect and manage various forms of data is increasing rapidly, although our ability to critically analyze all of this data and its potential significance to slope stability is not (yet) increasing at the same rate.  This paper investigates the Cumba slope failure, a 70-meter-high non-daylighting planar rockslide, which occurred in the Dominican Republic in 2019. The investigation and technical review utilizes and integrates all available data to improve the geotechnical model, inclusive of key geological inputs, major structure, rock mass constitutive models and groundwater. Data from aerial photogrammetry and ground-based synthetic aperture radar data are used in conjunction with three-dimensional limit equilibrium analysis techniques to develop realistic simulations of ground behavior that are qualitatively and semi-quantitatively. Three-dimensional analysis results are compared with two-dimensional cross-sectional analyses. With the strategic combination of available information, it was possible to complete this technical review in less than one week and demonstrate the benefits of technology integration in geotechnics. 

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