The Tunnel's Path
VTA’s BART Silicon Valley Phase II Extension Project includes the construction of a tunnel that will be approximately five-miles long. Tunnel construction will begin south of the Santa Clara Station within Newhall Yard and run underneath I-880 and the Caltrain tracks. It will be launched from what is referred to as the West Portal. From there, the tunnel will continue southeast and cross under the western side of the Caltrain tracks at Emory Street and then continue under Stockton Avenue and curve east before reaching Diridon Station. From Diridon Station, the tunnel will continue under Santa Clara Street for approximately one-mile to the future Downtown San José Station. It will then curve northeast near 27th Street and Santa Clara Street to the future 28th Street/Little Portugal Station. From there, the tunnel will continue northeast under US 101 to McKee Road where it will run parallel to the highway until it surfaces at the East Portal, near Las Plumas Avenue and Marburg Way.
Tunneling Construction
Construction of the subway tunnel is within the Tunnel and Trackwork contract (Contract Package 2). The tunnel will be constructed as a single, large diameter tunnel, commonly referred to as Single-Bore, and will contain two independent track ways, one for each direction of travel. The tunnel will be excavated by a Tunnel Boring Machine (TBM). The TBM is an electrically powered machine that removes soil, rocks, and debris to create the underground tunnel. It features a cutter-head, which rotates to dig through soil and rock. Excavated material is removed through a conveyor system within the machine. The TBM will be able to excavate and build approximately 30 to 40 feet of the tunnel per day on average. At the stations, mining techniques will be used to excavate the underground connections between the tunnel and stations (which contain the boarding platforms). Tunneling is expected to occur 24 hours a day, up to 7 days a week to excavate and support the five-mile tunnel.
How a Tunnel Boring Machine (TBM) Operates
A Tunnel Boring Machine (TBM) will remove soil from the tunnel itself, keeping the street above intact. The TBM includes a cutter-head, which rotates to dig through soil and rock. The excavated material will then be removed through a conveyor system within the machine. TBM boring speeds vary greatly, depending on the size and length of the tunnel, the geological conditions, and many other factors. The following video demonstrates how TBMs work.
Check back in mid-2024 to learn more about naming the TBM!
The Tunnel's Path
VTA’s BART Silicon Valley Phase II Extension Project includes the construction of a tunnel that will be approximately five-miles long. Tunnel construction will begin south of the Santa Clara Station within Newhall Yard and run underneath I-880 and the Caltrain tracks. It will be launched from what is referred to as the West Portal. From there, the tunnel will continue southeast and cross under the western side of the Caltrain tracks at Emory Street and then continue under Stockton Avenue and curve east before reaching Diridon Station. From Diridon Station, the tunnel will continue under Santa Clara Street for approximately one-mile to the future Downtown San José Station. It will then curve northeast near 27th Street and Santa Clara Street to the future 28th Street/Little Portugal Station. From there, the tunnel will continue northeast under US 101 to McKee Road where it will run parallel to the highway until it surfaces at the East Portal, near Las Plumas Avenue and Marburg Way.
Tunneling Construction
Construction of the subway tunnel is within the Tunnel and Trackwork contract (Contract Package 2). The tunnel will be constructed as a single, large diameter tunnel, commonly referred to as Single-Bore, and will contain two independent track ways, one for each direction of travel. The tunnel will be excavated by a Tunnel Boring Machine (TBM). The TBM is an electrically powered machine that removes soil, rocks, and debris to create the underground tunnel. It features a cutter-head, which rotates to dig through soil and rock. Excavated material is removed through a conveyor system within the machine. The TBM will be able to excavate and build approximately 30 to 40 feet of the tunnel per day on average. At the stations, mining techniques will be used to excavate the underground connections between the tunnel and stations (which contain the boarding platforms). Tunneling is expected to occur 24 hours a day, up to 7 days a week to excavate and support the five-mile tunnel.
How a Tunnel Boring Machine (TBM) Operates
A Tunnel Boring Machine (TBM) will remove soil from the tunnel itself, keeping the street above intact. The TBM includes a cutter-head, which rotates to dig through soil and rock. The excavated material will then be removed through a conveyor system within the machine. TBM boring speeds vary greatly, depending on the size and length of the tunnel, the geological conditions, and many other factors. The following video demonstrates how TBMs work.
Check back in mid-2024 to learn more about naming the TBM!