Strategies for Mining in the Vicinity of the Creighton Fault at Vale Inco’s Copper Cliff Mine
ABSTRACT: The mining of the 880 ore body at Copper Cliff Mine accounts for more than 50% of the mine’s scheduled production. The Vertical Retreat Mining method is used with stopes that are typically 150-ft in height and 50-ft by 50-ft on section. Most of the stoping is transverse with mining starting on the hangingwall and retreating to the footwall contact. A mine-and-fill process is used to control the volume of open ground and to also mitigate ground stability issues within the stopes and in the adjacent mining areas.
The majority of the stopes have been mined without any significant ground control issues although a section of the ore zone intersects the Creighton Fault. This structure is located on the south side of the ore zone and the mining history has shown the fault to be benign in terms of seismic activity. The fault, however, has created a weak zone of boundary rock along its contact and this represents the greatest a challenge for mining in terms of controlling dilution and maintaining rockmass stability.
This paper discusses the previous mining and the impact of the fault on the ore recoveries and ground stability. The paper then outlines the results of a recent geomechanical study whereby numerical analyses and empirical designs were used to better predict the ground response to mining for two stopes, 651 and 652, located between 3290 level and 3400 level. Recommendations on the approach for mining these stopes are discussed based on the calibration results from mining of previous stopes in Creighton Fault area.