Deep drive at El Teniente starts

The contract, which Vinci won in September, is split 60:40 between Vinci Construction Grands Projets and Vinci subsidiary Soletanche Bachy and is valued at USD 400M. The scheduled work is part of the New Mine Level Access Tunnels developments at a deeper level to ensure continued production at the mine for another 60 years and will improve mine access during high snowfall. There will be two interconnected tunnel, each 9km long, 9m high, and average sectional area 65 square metres, with one providing personnel access using trackless vehicles and the other a route for a belt conveyor for ore and rock removal. There are also two intermediate access tunnels each 6km long. The mine is located at an altitude of between 1500 and 1900m in the Andes mountains 80km south of Santiago in the Libertador General Bernado O’Higgins region. The ground at the tunnel’s level includes strong volcanic deposits, metamorphic structures and some weak rock in fault zones. Experience with the Rio Blanco TBM water supply drive in the 1990s showed the volcanic rock to be of good quality but the presence of minerals that swelled in the presence of water caused subsequent spalling problems. Initially two Robodrill drilling jumbos are being employed in drill-and-blast excavation in the hard, but this is due to rise to a total of twelve excavation rigs and at least one Montabert 108 dedicated rock bolting rig. Half of the drill-and-blast rigs on order are computerised Robofore 3-boom units, and the others are manually operated Pantofore twin-boomers with an HL150 basket boom. The Robodrills, made near Lyon in France, feature Montabert HC 110 HF (high-frequency) hydraulic drills capable of 3.5-3.8 m/min drilling speeds on the 3-boom rigs and HC 108 drills on the twin-boom rigs. Robodrill’s supply contract includes a full maintenance and support package. The overall planning and design for development of the new level has been carried out by Hatch mining engineers of Mississauga, Canada and Chile with the full support Hatch Mott MacDonald of Vancouver, Rockville and Loa Angeles, and Mott MacDonald of the UK. (See Chamy et al 2010 – ‘Planning and design for the New Mine Level Access Tunnels at El Teniente, Chile’, Proc World Tunnel Congress, Vancouver.) Vinci itself is carrying out detailed design in the design-build contract. Vinci’s work is scheduled to take 40 months