3-Dimensional Numerical Modelling of Stope Sequencing for Mine Planning

Rock Engineering 2009 - Rock Engineering in Difficult Conditions
Hani Mitri, Eric LeComte, Normand Bedard,
Abstract 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
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