Artificial Crown Pillar Construction and In Pit Tailings Disposal at Agnico Eagle's Pinos Altos Complex, Mexico

Underground Geomechanical Challenges and Tailing Management


Veronique, Falmagne

The Oberon de Weber open pit is part of the Pinos Altos Mining Complex owned by Agnico Eagle Mines Ltd, in Mexico. A project was initiated in 2013 to enable the deposition of tailings in the soon to be exhausted Oberon de Weber Open Pit while mining the underground portion of the deposit extending below the pit. A conceptual plan for constructing the tailings facility and mining the crown pillar below it was proposed. A series of investigations, preliminary and detailed studies and a risk assessment were conducted to prepare a plan that was technically sound, safe, and environmentally secure during operations and after closure. Several alternatives were considered and analyzed for optimizing the recovery of the high-grade ore. Economic and technical analyses supported the construction of an artificial crown pillar within a narrow trench excavated at the pit bottom combined with a 10 m rock pillar above the underground stopes. The construction of the facility including water management and instrumentation of the crown pillar are presented. The Oberon de Weber TSF is in operation since the end of 2015 and is performing well while the crown pillar extraction has been successful, exceeding the planned resource recovery.
Keywords: CIMBC22