Evaluating Large-Scale Pit Slope Stability Methods


In September 2022, the Large Open Pit research project (LOP) initiated a review of large-scale pit slope stability methods. The project was triggered in part by the evolving needs of the industry and in part by a conference publication and a keynote address by Dr. John Read at the 2021 Slope Stability in Mining Conference in Perth, AU. Citing extensively documented formulation issues, Dr. Read’s keynote highlights that the “reliability of 3D LEM (three-dimensional limit equilibrium method) is causing debate within the industry,” calling into question the appropriateness of associated Design Acceptance Criteria (DAC). Dr. Reid’s comments open up a broader conversation on the need for guidance on the use and applicability of various slope stability methods. Recent advancements in the field of computational geomechanics gave rise to a number of technologies and methods for evaluating slope performance, as well as expanded our understanding of existing slope stability methods and their limitations. These developments are the primary driver behind LOP’s interest in obtaining updated guidance in these matters. The project seeks to establish the applicability and usability of various slope stability analysis methods specifically for rock slopes and pit wall slopes, with a primary focus on multi-bench failures. Some of the project objectives include:

  • A literature review of the common methods used in slope stability assessments, focusing on their limitations. Of special interest are: (a) formulation and implementation errors and their qualitative and (if possible) quantitative effects on the analysis outputs; (b) assumptions and simplifications and their effects on the output; (c) the interpretation of results; and (d) the applicability of methods.
  • One or more pit wall instability case studies with sufficient background data to complete slope stability analyses using a range of slope assessment methods. The intent is to have geotechnical software developers and investigators conduct slope stability analyses using any number of methods for discussion in an online workshop.
  • A cursory assessment of the issues raised by Dr. Read, based on the literature record.