SAN FRANCISCO - The Valley Transportation Authority reports that it has purchased a tunnel boring machine from Herrenknecht, for its BSVII, or BART Silicon Valley Phase II, project.
The Valley Transportation Authority reports that it has purchased a tunnel boring machine from Herrenknecht, for its BSVII, or BART Silicon Valley Phase II, project. Herrenknecht is a German manufacturing company that builds these types of specialized tunneling equipment. The machine will dig the tunnel, which will contain “five miles of train tracks in both directions and three station platforms to provide safe and efficient travel separated from congested roadways.”
VTA says it will prepare for the TBM by constructing on-site access points, establishing an excavated materials bin, excavating the portal, and constructing and operating the facilities needed to produce the tunnel lining.
The machine, which costs $76 million, will be one of the biggest built at almost 54 feet in diameter (48 feet in diameter for the interior), and “multiple payments will be made to the manufacturer at key milestones of design, production, delivery, assembly, and launch of the TBM.” The TBM will be designed for this project’s unique requirements. According to the VTA, the tunnel’s size was “determined by the space needed for the tracks, trains, boarding platforms and other equipment and facilities needed in the tunnel to operate safely and efficiently.” As soil is removed, cement tunnel lining segments will be installed to ensure a “structurally sound tube underground.”
The TBM will remove soil from underground to form the tunnel. The front “includes a cutter-head, which rotates to dig through the soil and rock. That material will then be removed through a conveyor system within the machine.” Below is a picture showing the inner workings of the Tunnel Boring Machine.
Herrenknecht will design and build the machine in Schwanau, Germany before being shipped to California 18 months after manufacturing begins. It will take around 6 months for the TBM to be assembled on-site at the West Portal. VTA reports that the TBM will “launch at the West Portal and will dig 30 to 40 feet each day traveling east towards the Berryessa/North San Jose BART Station, taking approximately 3 to 4 years to complete the 5-mile-long tunnel.” At that time, the TBM will come above ground at the East Portal near Las Plumas Avenue where it will be disassembled. Remaining materials will be reused “to the extent possible.”