Synthetic Rock Mass Modeling of Progressive Unravelling and Overall Slope Stability Using the Discrete Element Method

Synthetic Rock Mass Modeling of Progressive Unravelling and Overall Slope Stability Using the Discrete Element Method

Authors: Rami Abousleiman1, Carlos Contreras2, Jim Cremeens1
Conference: Slope Stability 2024
Date: April 14-19, 2024

1 Knight Piésold and Co., Denver, USA
2 Stantec, Lima, Peru

ABSTRACT

Mining of epithermal gold deposits often encounters a wide range of rock mass conditions in a single excavation. Selecting the appropriate representation for design and analysis in variable ground conditions is critical. Continuum representation of rock masses in numerical or analytical methods used in state-of-practice slope design simplify the complex relationship between intact rock and discontinuities. Continuum methods are generally accepted for end-member strong or weak rock masses but cannot explicitly consider the effect of discontinuity orientation, separation, and material bulking on slope stability. Discontinuum methods often require the user to provide pre-determined failure surfaces, which can bias the model results when used for predictive modeling or design. Hybrid methods exist, but can require significant computational power and require extensive calibration.

This study utilizes the synthetic rock mass (SRM) approach by combining the Generalized Hoek-Brown and Mohr-Coulomb Strain Softening constitutive models available in Itasca’s Universal Distinct Element Code (UDEC) to represent intact material and discontinuities, respectively. Where appropriate, discontinuities were assigned an equivalent Mohr-Coulomb strength based on previously developed Hoek-Brown parameters during initial domain development for pit slope angle recommendations. The numerical model was used to analyze a case study from an open-pit gold mine failure of a weak, in-dipping fault-zone that resulted in the propagation of failure and unravelling of a 18 m bench of otherwise competent rock. Numerical model results were compared to the observed deformation and survey monument displacement data. Following confirmation of realistic model behavior, the model was used to evaluate the design of a proposed layback and buttress to continue mining safely.

 

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