Boring completed on West Gate Tunnel

TBM Bella made the final breakthrough at the West Gate Freeway in Victoria last week, completing a 4km journey digging the outbound tunnel between Williamstown and Millers Road in South Kingsville.

In February, TBM Vida completed excavation of the 2.8km inbound tunnel, starting on the west side of the Maribyrnong River, continuing under Yarraville and finishing at Williamstown Road near the West Gate Freeway.

The two Herrenknecht EPBMs will be dismantled and removed piece by piece, while the 450t cutterhead will be buried on-site and other components either recycled or returned to the manufacturer.

Bella and Vida are the largest TBMs in the Southern Hemisphere – each with a 15.6m diameter, 90m long and weighing 4,000 tonnes.

The EPBMs were chosen because of the presence of residual basaltic clays with sections of weak to solid rock and alluvial silty clays in addition to a section with hard basalt up to 250MPa. The EPBMs were designed to manage all these conditions, incorporating advanced ground conditioning systems and a high specification of wear protection.

The twin tunnels are lined with a precast segmental lining in a 10 + 0 configuration, held together by 20 circumferential bolts. The lining has an internal diameter of 14.1m and is 500mm thick with a 40mm universal taper.

The segments are 2.4m long, which are claimed to be the longest segments in the world.

The West Gate Tunnel, due to open in late 2025, is designed to ease congestion on the West Gate Freeway and West Gate Bridge, and reduce the number of trucks on residential streets.

The project is a public private partnership (PPP) between the Victorian government and Transurban, a toll road operator. CPB Contractors and John Holland Joint Venture (CPBJH JV) was awarded the design and construction contract and Aurecon and Jacobs carried out the design work.