Kimberlite Bulk Sample, Vertical Cutter Mining (2018-2020)
Client: Rio Tinto Exploration Canada Inc.
In partnership with Bauer Maschinen GmbH (Bauer), Nuna has introduced to the mining industry the first cutter in the world capable of cutting to a depth of 250 m in a commercial application. The Cutter Rig comprises a Bauer BC 50 vertical cutter mounted on a MC 128 duty-cycle crane. Under contract to Rio Tinto Exploration Canada Inc., Nuna Bauer Joint Venture commenced vertical cutting services for a 3-phase kimberlite bulk sampling program comprising up to 30 holes (trenches) measuring each 3.2 m x 1.5 m with a maximum depth of 250 m. The project was managed by Nuna; and other than the Cutter Rig, all equipment was operated by Nuna personnel.
Mobilization & Site Establishment
Nuna Bauer Joint Venture mobilized a BC 50 vertical cutter and MC 128 duty-cycle crane (together referred to as the Cutter Rig), along with a BE-550 separation / desanding plant, conveyors, HP-50 hose pump, and a bentonite mixing plant from Germany. Support equipment for the erection of the Cutter Rig and the separation / desanding plant included a 120-tonne crane, a 70-tonne crane, loaders, telehandlers, and manlifts. Support equipment was mobilized from Edmonton and materials were sourced locally in the region.
Nuna carried out the site establishment scope utilizing excavators, dozers, loaders, a packer, articulated trucks, a fuel/lube truck, and pickup trucks. The scope included consolidation and relocation of numerous piles of processed kimberlite prior to construction activities; construction of a 2,000 m3 capacity lined, double-celled bentonite pond; and construction of various pads for the Cutter Rig, a BG 30 drill rig, the desanding plant, mechanic shop, and the cement mixing station. A total of 1,100 m2 of Portafloor was placed under the desanding plant pad, mechanic shop, and cement mixing station with rig matting being used to stabilize the pads around the trenches. 3,000 linear metres of 6” HDPE pipe was fused for water supply, bentonite movement, and sample recovery. The sample recovery pipe had the internal bead removed after being fused for maximum retrieval of the product.
Kimberlite Bulk Sample Sequence
The Cutter Rig was specifically designed to reach a maximum depth of approximately 250 m. The first 110 m to 120 m of a trench are considered overburden with the remaining 130 m to 140 m in kimberlite. The material is pumped from the Cutter Rig to the desanding plant and while the overburden material is being trenched, the desanding plant moves the “waste” which is collected and trucked to a stockpile location in preparation for backfilling. When the sample horizon is reached, the feed line is switched from the desanding plant to a kimberlite separation unit and a sample is taken every 10 m. These samples are washed in the “big bag” station on the desanding plant and placed into mega bags for processing. After the desired depth has been reached in the trench and the sample has been recovered, the Cutter Rig is moved to the next location, along with all feed and return lines. The final step in the trenching process requires backfilling. The material is put back in the trench consistent with the original location: the processed sample is filled first, followed by a bentonite chip seal of 10 m (to ensure a distinction between the sample and overburden horizons), and finally overburden. This technology, adapted from the foundation industry, is a unique innovative approach to bulk sampling where a large volume of kimberlite is required to support resource evaluation.
Site Access Road
Prior to mobilizing into the FalCon site for the kimberlite bulk sample program, significant upgrades were required to the 30 km site access road which included the installation of a bailey bridge. Nuna mobilized water trucks, haul trucks, excavator, dozer, loader, grader, tractor with wobblies, smooth drum packer, fuel truck, mechanic’s truck, pickups, and crew for the road upgrade scope. Work was carried out over a one-month period and comprised the installation of 250 linear metres of Neo-web reinforcement material, 3,075 linear metres of Combi-grid, and haul and placement of 2,430 m3 sand and 8,373 m3 gravel for road topping. Road grading, contouring, and compacting completed the road activity.