State Route 99 Tunnel:Formwork Solution forDouble-Deck Tunnel

The 1950s vintage Alaskan Way Viaduct has long been considered one of the most important thoroughfares along Seattle‘s waterfront in Washington, USA. As a replacement for the elevated viaduct that is used daily by 110 000 vehicles, a 3.2 km long tunnel is currently being constructed. Peri planned and delivered a project-specific formwork solution for the realization of the double-deck carriageway whereby the previously bored tunnel tube length is being concreted in three sections each time.

A Replacement for the Alaskan Way Viaduct

After the Alaskan Way Viaduct had suffered considerable damage due to a major earthquake in 2001, initial preparations were made for a replacement. Eight years later, plans for a bored tunnel emerged. In 2011, Seattle Tunnel Partners (STP) was awarded the contract for the design and construction of the tunnel – a joint venture of the Tutor Perini Corporation from California and Dragados USA.

Bertha, one of the world‘s largest tunnel boring machines (TBM) excavated a tunnel with a diameter of around 17.50 m was then directly lined with 60 cm thick precast...

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State Route 99 Tunnel: Formwork Solution for Double-Deck Tunnel

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