The Large Open Pit Project (LOP) is working on updating the guidelines on Design Acceptance Criteria (DAC) for open pit slopes. A proposed DAC reliability-risk based matrix for for open pit slope design at the overall and inter-ramp scales has been proposed and is currently under consideration by the LOP sponsors (see article attached). This proposed DAC matrix has been developed based on:

  • Industry’s experience with the implementation of previously proposed criteria;
  • Feedback at the SASORE conference that a matrix approach to prescribing Design Acceptance Criteria is preferred;
  • Published open pit design accepted DAC pairs of Factor of Safety (FoS) and Probability of Failure (PoF) relative to failure consequences; and,
  • The mathematical background that associates the mean FoS and PoF through the Coefficient of Variation (COV) of the respective Probability Density Function, which represents one measurement of design reliability.

The proposed DAC focuses on operational/economic consequences of slope failure. The proposed DAC matrix has a robust mathematical and empirical base. However, validation, and ultimately endorsement of its application, requires stress testing the DAC matrix via published (and un-published) case studies to establish confidence in it’s application to pit slope design. The case studies should be of pit slope designs that have been accepted and implemented .

We are reaching out seeking your support in sharing pit design reports that can be used to stress-test the proposed DAC matrix. The information required is outlined in the attachment. No information will be disclosed outside the working group (individuals in this email) without explicit written consent of the owners of the information, and results will only be shared in an aggregated and anonymized manner as part of the stress-test results and reports.

The case studies will be used to:

  • ‘Road Test’ the matrix approach to prescription of target DAC to slope at various stages of slope design development;
  • Confirm that the prescribed target DAC, are aligned with the broad risk tolerance associated with pit slope design; and,
  • Identify any improvements/amendments that may be required.

To lessen the burden of this request, pit wall and pushback design reports are welcome.

Please do not hesitate to contact me or Renato (macciott (at) ualberta.ca) if you have any questions and for the method that suits best for sharing design reports.