DRILL & BLAST
T V THEERTICALATTACK
rench cutter technology, being a typical civil engineering method, has been used in recent times in various bulk sampling and trial mining applications. Nowadays, the cutter system technology has been further developed from applications in exploration and mining to a sustainable system for selective mining with one focus on near- vertical gold veins. Trench cutters are widely used in civil engineering for the installation of diaphragm walls and cut-off walls. Diaphragm walls act as retaining walls to allow for open excavation pits, e.g. for the installation of underground car parks and subway lines, and foundations of buildings. Cut-off walls underneath and inside dams, also tailings dams, act as permanent water barrier to avoid seepage and collapse of the dam. To form the walls, trenches are excavated by the trench cutter in primary and overlapping secondary panels. Te panels are supported by bentonite slurry during excavation, and backfilled with concrete, replacing the slurry, upon completion. During excavation, bentonite slurry in civil engineering and water in mining, is mixed with the crushed rock and pumped to surface, where it is separated in a treatment plant. Te cleaned slurry, or water, is pumped back to the cutter excavation in a closed loop to minimise consumption.
Stefan Schwank and Ulrich
Schoepf discuss a modern way to tackle gold veins
Bauer has been developing its trench cutter system for many years and is considered an expert in the sector, with more than 400 units working around the world. Key components of a trench cutter are two counter-rotating cutter wheels that can be fitted with different teeth arrangements for excavation of all different types of soils and rocks. Te cutter wheels and recovery
pump are mounted inside a heavy steel frame that is equipped with hydraulically operated steering plates to control verticality or planned inclination in both directions. For better penetration in harder formations, especially in mining, the hard rock cutter system (HRCS) is mounted between the cutter frame and the cutter wheels. Te locking system is designed for higher and constant load on bit compared to the free hanging system and transfer the loads applied into the sidewalls of the trench.
Both the mud delivery and the
hydraulic hoses with electric cable are automatically fed into the trench and coiled up on drums positioned on the back of the rig. For moving the rig easily from one position to the next, the entire system is mounted on a crawler-based carrier that also provides sufficient engine power for the entire unit. As an alternative, electric power can also drive any of the Bauer cutter units.
Bauer cutter for 250m depth on Rio
Tinto Falcon project, Canada
12
www.engineerlive.com
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