Numerical model parametric study on the effect of stope undercutting

Rock Engineering 2009 - Rock Engineering in Difficult Conditions
Hind Zniber , Hani Mitri, Eric LeComte, Normand Bedard,
Abstract Ore dilution or stope overbreak influences the cost of production and ultimately the profitability of a mining operation. The economic impact of ore dilution is due to the added costs associated with the mucking, haulage, crushing, hoisting, milling, and treatment of waste rock or low grade ore in the hangingwall and footwall. One factor that could have a significant influence on stope overbreak is the undercutting of the stope into the walls. Undercutting stope walls is sometimes necessary, in particular in narrow vein exploitation. Moreover, equipment size has a role in drift sizing where stope undercutting is obligatory to fit the mobile equipment while respecting legal clearances.

This paper presents a numerical model parametric study to examine the influence of stope undercutting on its overbreak with geomechanical data obtained from the Lapa Mine of Agnico Ealge Mines Limited. The study compares two scenarios of stope undercuts namely 1m and 0.4m to a hypothetical case of no undercut. Numerical modeling is carried out with elasto-plastic finite elements using the finite element software Phase2. Overbreak is estimated using a simple criterion of comparing mining induced stress in the stope walls to the tensile strength of the rock mass. While 2-dimensional modeling is approximate, the study nevertheless demonstrates the role that stope undercut could play on wall overbreak.
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