In many engineering projects, the design engineer forms an integral part of the construction team. The design engineer can monitor the implementation of the design and assess if any construction conditions deviate from the design assumptions. Mining of an open pit slope requires monitoring; while this is mostly performed by the mine’s geotechnical team, the involvement of the design team has many benefits. Open pit slopes are generally designed based on a point in time of a geotechnical model, which evolves as the pit expands. This is due to the variability associated with geological environments, limitations in data and exposure uncertainties. As the geotechnical model evolves, so too should the design. Additionally, the measures that are put in place to manage the risk associated with the slope design must be aligned with the uncertainties in the geotechnical model and design assumptions. Benefits of a long-term relationship between mine personnel and the design consultant include ongoing review of the slope performance with time and continuity in understanding of the risks and geotechnical model; the ability to provide input into instability management and back analysis with an understanding of the history of instabilities and slope performance; a thorough understanding of the litho-structural model, groundwater model and the geotechnical data base, their development over time and the resulting limitations, and the ability to make contributions to future development; institutional memory preserved when mine staff change; and practical exposure of mine staff to stability analysis and the slope design process.
In addition to the above, due to SRK’s long-term development in these fields, SRK can assist the mine in transitioning to UAV-based data collection and conducting detailed third-party review of the mine’s micro-seismic monitoring. Additional advanced analysis of the micro-seismic data provides further input into slope behaviour analysis and model calibration.
The Rossing uranium mine is a ~20 Mtpa (total tonnes mined) ~390 m deep open pit uranium mine that has been operating since 1976. It is 70 km inland from the coastal town of Swakopmund in Namibia. SRK South Africa has been providing mining geotechnical consulting services since 2013 in the form of training, mentoring, guidance and review. Regular site visits are conducted to review and provide mentorship to the mine’s geotechnical team, and to keep them abreast of developments and advances in open pit slope design, management, monitoring and data collection technologies. Additionally, design updates are conducted as new knowledge is gained for incorporation to the geotechnical model.
