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Super•Cor® takes flight for Galore Creek avalanche protection.
The Galore Creek Mine, located in a remote, mountainous area of northwestern British Columbia, is one of the largest mining projects under development in Canada. The project is being developed by NovaGold Resources and Teck-Cominco and comprises one of the largest and highest grade undeveloped porphyry-related gold-silver-copper deposits in North America. In order to access this planned high-tonnage, open-pit operation, a new 120km road is being constructed including a 4.4 km mine access road tunnel, which will be the longest private road tunnel in North America.
Challenges: Only accessible by helicopter, 5 m of snow cover.
Much of the tunnel alignment is covered by glaciers and receives some of the highest precipitation in North America with a snowpack height over 5 m (16 ft). The northern portal was first to be constructed but was only accessible by helicopter, adding logistical challenges for moving labor, material and equipment. It sits within a large glacial bowl/scarp with slopes ranging from 35 to 56 degrees and an adjacent ice-fall glacier of 300 m (985 ft) in height. The large portal area excavation only exacerbated an already-high avalanche/rockfall risk and a robust but economical protection canopy was needed quickly.
Super•Cor® structure cost much less than concrete and was easily flown in.
Lead project design engineer, Peter Proctor of Hatch Mott MacDonald, opted for a solution using Super•Cor® structural plate from Atlantic Industries Limited (AIL). AIL Technical Reps had demonstrated how their deep-corrugated Super•Cor® structure would be much less expensive than concrete and how easily its modules could be flown in by helicopter and quickly assembled on site. Super•Cor® also had the strength to withstand the potential avalanche/rockfall loads and the galvanized longevity to deliver a long-lasting and maintenance-free design service life.
AIL's MSE Structural Wall System also used.
The AIL team also recommended their MSE Structural Wall System for the headwalls to meet backfill requirements and facilitate the construction of avalanche deflection berms on top of the backfill zone.
AIL helped owner optimize costs over course of project.
AIL's in-house engineers designed the structures to accommodate prescribed dead, live and exceptional loadings of rockfall, snow (both static and avalanche impact), accumulated soil fill and seismic activity. The canopy was subdivided into zones to accommodated different loadings by adding external intermittent reinforcement ribs. With overall mine development costs headed for a review, the AIL team was able to respond and help the owner realize additional savings by optimizing the gauge of steel used over the length of the structure while still meeting load criteria.
Structure largest of its kind ever built.
The structure was made from SC72R Super•Cor® Round with an inside diameter of 9.2 m (30 ft) and a length of 66 m (216 ft). With a substantial end area of 50 m2 (538ft2), it is believed to be the largest structure of its kind ever fabricated. In the fall of 2007, the canopy required 19 days to build and the headwall and backfilling took 20 days with weather delays.
Hatch Mott MacDonald managed the overall design, with key design input from Chris Stethem and Associates Ltd. and BGC Engineering Inc. MEG Consulting Ltd. provided quality assurance monitoring for earthworks placement.
Special note: During 2008, Galore Creek Mining Corporation, the operator of the Galore Creek project, temporarily halted construction and undertook an extensive engineering review to look at optimization of the development plan. The results of these studies have identified a number of modified approaches to the project that show the potential for significant expansion of the project throughput, a shorter construction schedule, location of the process facilities to allow for future expansion, and fewer risks associated with construction and operations.
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