Managing Excessive Pit Wall Deformation of Weak Rock Mass

Managing Excessive Pit Wall Deformation of Weak Rock Mass

Authors: Salina Yong, Daniel Yang, Justine Ealy, Christina Foster
Conference: International Slope Stability 2022 Symposium
Date: October 17-21, 2022


Rapid acceleration of a large-scale creeping instability occurred in an open pit operation in 2016. A 150-foot-tall back scarp formed, tension cracks appeared near the pit rim, bulging formed in the lower slope, and debris reached the pit bottom. The instability displaced material over a hundred feet and buried the main access road. Monitoring of the initially slow-moving mass had commenced in 2013 with terrestrial radar, which was integral to managing the risk along with strategic mine planning. As a result, the instability was successfully managed and did not lead to safety incidents or equipment losses. Re-establishing access necessitated routing through the slide debris, which posed a risk to the road development due to the potential of heightening the back scarp. Dewatering and removal of the slide toe also posed risks to the road development and mine economics.

Analyses were completed to evaluate the stability of the back scarp and the proposed mining sequence of the slide toe with UDEC, RocFall, and Slide3. The analyses assisted rehabilitation by identifying influential factors, estimating the rockfall impact, and identifying areas of concern. The pit was successfully rehabilitated, not only with the insights provided by the analyses but also the vigilant guidance provided by the mine geotechnical team through real-time slope monitoring and inspections, continuous maintenance, and a flexible mindset for impromptu adjustments when needed. Mining of the pit was completed in 2020 and backfilling is ongoing. Recent monitoring data indicates the instability has stabilized at a displacement rate of nearly zero. This paper summarizes a case history where excessive deformation of a pit wall exposed in weak rock mass was successfully managed.


Download the full paper.


Recent Insights

July 2023
Selection of Soil Shear Strength Parameters Based on Integrated In Situ Tests, Lab Tests and Numerical Calibration Approach
June 2023
Leveraging Knowledge and Experience of a Well-Formed Independent Tailings Review Board to Enhance Tailings Facility Safety
May 2023
Is the Implementation of Dry Stacking for Tailings Storage Increasing? A Southern African Perspective
February 2023
Canadian Consulting Engineer's Lifetime Achievement Awards: Jeremy Haile
February 2023
Geotechnical Characterization of Collapsible Salty Sands Subjected to Monotonic and Cyclic Loadings – A Case Study for Areas with High Seismicity
November 2022
Application of the 3D Limit Equilibrium Method in Tailings Dam Breach Analysis
November 2022
Evaluation of Tailings Behaviour for Dam Breach Assessments
November 2022
Tailings Improvement by Stress-Densification from Waste Rock Capping
November 2022
Transforming Tailings Management Systems toward Alignment with the GISTM: A Case History
October 2022
State-of-the-art Method for Estimating Long-term Hydroclimatic Conditions for Tailing Dam Water Management and Dam Safety Planning
August 2022
Observed Subsidence Progression at New Afton Mine in Response to Lift 1 Mining
June 2022
Hydrometric Monitoring and Effluent Discharge Mixing in Challenging Natural Conditions
May 2022
Inundation Modelling of Non-Newtonian Tailings Dam Breach Outflows
May 2022
Video: Tailings Management Compliancy Picks Up Momentum
May 2022
A Catch up with...Richard Elmer
February 2022
Engineer of Record Services for Tailings Facilities
November 2021
Knight Piésold's Projects Commended at Prestigious Awards
November 2021
Advances in Ensuring Tailings Dam Safety
November 2021
Gearing Up for Growth in Zambia