Robbins supplied an EPB TBM to the San Francisco, US Central Subway scheme, where it had to negotiat

Robbins supplied an EPB TBM to the San Francisco, US Central Subway scheme, where it had to negotiate changing geology, steep grades and tight turns.

A joint venture including Salini Impregilo has reached completion on the tunnel for Central Subway project to extend the San Francisco, US subway. Part of the Third Street Light Rail Transit Project, the scheme is designed to reduce air and noise pollution as well as traffic congestion in the city’s downtown area.

Central Subway comprises a light rail line that will improve public transportation to and from some of the city's busiest, most densely populated areas, including the Visitacion Valley and Bayview/Dogpatch.

The total project is to cost US$ 1.6 billion, US$ 241 million of which was set for the work done by the tunnelling joint venture, which comprised Salini Impregilo, its US unit S.A. Healy and partner Barnard C.C.I. Work on the 2.4 km twin tunnels and five cross passages was completed a month ahead of schedule.

Salini Impregilo general manager for international operations said, “This work is the latest example of the Group’s engineering experience and ‘know how’ that make Salini Impregilo a benchmark in the sector of complex public works throughout the world, even in countries with a developed infrastructure network like the United States.”

Robbins supplied the earth pressure balance (EPB) tunnel boring machine (TBM) for the scheme. A mixed face cutterhead was selected d to excavate the anticipated wide variety of ground, while active articulation was integrated between the TBM shields to lessen the risks of segment damage, ring deformation, and settlement during boring through curves. Robbins continuous conveyors were used for muck removal throughout tunnelling.

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