Effective Stress In Large Open Pit Slopes

Provider: Piteau Associates UK Limited


Understanding groundwater flow, pore pressures and effective stress in pit slopes is vital for the delivery of economic and safe slope designs.  Pore pressure is one variable controlling slope stability which can be measured, simulated, predicted and, through pro-active intervention, effectively managed to achieve a pre-determined outcome. Notwithstanding the recognition of the importance of effective stress and pore pressures on pit slope stability, there remains across the mining industry a relatively poor understanding of:

  • groundwater flow in a fractured medium, which is leading to incorrect analysis and poor conceptual model development
  • effective stress in a fractured rock masses, and how this changes with time in response to mining;
  • the limitations of industry applied techniques to the prediction and application of pore pressures into pit slope design;
  • constraints to the application of commonly adopted approaches such as Equivalent Porous Media (EPM) to some problems; and,
  • the significance of the coupled deformation/pore pressure response on pit slope stability.

Within LOP II, a unique opportunity has been identified, comprising the utilisation of an extensive, comprehensive, world-class data set from the Rio Tinto, Bingham Canyon Mine (BCM) drainage gallery project, comprising both the South Wall Drainage Gallery (SWDG) and the North Wall Drainage Gallery (NWDG), to improve the industry knowledge of groundwater flow, pore pressure, pore pressure response to mining and the application of effective stress within one of the largest open pits in the world. This research proposal outlines a phased programme of work to further our understanding of groundwater, pore pressure and effective stress in deep open pits.