3-Dimensional Numerical Modelling of Stope Sequencing for Mine Planning


Hani Mitri, Eric LeComte, Normand Bedard,

There are many inherent risks in creating a mine plan for a new ore zone in an underground mine; one of such risks is the redistribution of stresses that could be a cause for concern of instability. Numerical modelling has been increasingly used as a powerful tool for the assessment of mine plans from a geomechanics perspective. Using numerical modelling tools, it is possible to model the planned stope extraction sequence and quickly evaluate the influence of mining induced stresses on the stability of remnant pillars, and use this information to remedy potential setbacks. This paper demonstrates this approach through a case study of the short-term mine plan of the Lapa mine of Agnico Eagle Mines Ltd., an underground gold mining operation near Val d’Or. Three-dimensional boundary element modelling is carried out to compute the stresses induced by the stope extraction sequence as planned with a longitudinal retreat mining method. Stability is assessed by examining mining-induced stresses in the vicinity of the mined stopes, as well as their progression with mining activities. Despite the inherent limitations of the linear elastic boundary element method, it is possible to gain a preliminary understanding of when the stress concentrations could become critical, thus alerting the mine planner to potential stability concerns. This methodology can be generalized to other mines that require an understanding of the stress concentrations at the pre-feasibility stage of mine design.
Keywords: Sequencing, induced stresses, Numerical modelling, Pillar stability