ROADHEADERS WITH cutters specially designed to deal with Sydney's hard Hawkesbury Sandstone are forming a number of tunnels under the Australian city.
Voest Alpine has nine of its roadheaders working in Sydney, on the Cross City road tunnel, the Lane Cove road tunnel and the Epping to Chatswood rail line - formerly known as the Parramatta Rail Link.
The Aus$1.1bn (£0.43bn) Lane Cove tunnel is the latest project, a key link in Sydney's motorway network connecting the Gore Hill Freeway at Artarmon with the M2 at East Ryde.
Construction is being carried out by a Thiess/John Holland joint venture, which began tunnelling in June. Two Voest Alpine ATM 105 machines will soon be joined by a further three to excavate the 3.4km twin, two- and three-lane tunnels under Epping Road and Stringybark Creek.
The electrically powered machines use Icutroc technology, developed by Voest Alpine and Sandvik.This includes a new stronger grade of cemented carbide pick to deal with the up to 150MPa rock, a optimised cutter head and reduced cutting speed which uses less energy.
Tunnelling is due to finish in early 2006, by which time about 650,000m 3of Hawkesbury Sandstone will have been removed.
The toll tunnel is due to open to traffic in 2007.
The contract was awarded to The Lane Cove Tunnel Consortium (Thiess, John Holland, Transfield Holdings and ABN AMRO) in October last year. Since then, Hong Kong-based Cheung Kong Infrastructure Holdings has acquired a 40% stake in the consortium.