74 articles
Sinking, joints and closure in immersed tube tunnels
Sinking, joints and closure in immersed tube tunnels covers how prefabricated tunnel elements are lowered onto the seabed, sealed with Gina and Omega gaskets, and closed at the final joint.
Slurry shield
A slurry shield is a tunnel boring machine that supports the tunnel face with pressurized bentonite slurry, best suited to coarse sand and gravel with high groundwater pressure.
Slurry tunnel boring machine
A slurry tunnel boring machine, commonly called a mixshield, is a TBM that supports the tunnel face with pressurized bentonite slurry, chosen where groundwater must be held under tight pressure control.
Snow Hill tunnel (London)
Snow Hill tunnel is a short railway tunnel beneath Smithfield Market in central London, opened in 1866 and reopened in 1988 to carry the Thameslink route between Blackfriars and Farringdon.
Top-down cut-and-cover construction
Top-down cut-and-cover construction, known in the industry as the Milan method, builds an underground box from the top down: walls and columns first, then the roof, then excavation beneath it.
Tower Subway
The Tower Subway is a tube tunnel under the Thames in London, opened in 1870 as the world's first tube railway and today carrying water mains and cables.
Trench dredging and foundations for immersed tube tunnels
Trench dredging and foundations for immersed tube tunnels cover dredging the trench to profile and supporting the elements on screeded gravel beds, pumped sand, grout, or piles.
Tunnel boring machine
A tunnel boring machine (TBM) is a large machine that excavates circular tunnels through rock or soil with a rotating cutterhead, erecting the tunnel's concrete lining as it advances.
Tunnel boring machine operation
Tunnel boring machine operation is the practice of launching a TBM underground, boring through variable ground, and salvaging or burying it, judged by advance rate and utilization.
Tunnel instrumentation and deformation monitoring
Tunnel instrumentation and deformation monitoring is the systematic measurement of ground and lining movement during tunnel construction, the core feedback loop of the New Austrian Tunnelling Method.
Underpinning
Underpinning is a construction method that deepens a building's foundations by excavating soil beneath them and replacing it with concrete, done in phases to strengthen or deepen inadequate foundations.
University Link tunnel
The University Link tunnel, also known as U Link, is a 3.15-mile pair of bored light rail tunnels in Seattle carrying Sound Transit trains from downtown to the University of Washington, opened in 2016.
Variable-mode tunnel boring machine
A variable-mode tunnel boring machine is a single TBM that can be reconfigured to tunnel in more than one ground-support regime, such as open, EPB, and slurry modes.
Work in compressed air
Work in compressed air, or hyperbaric work, is construction labor in chambers pressurized above atmospheric to hold back groundwater in soft-ground tunnels and caissons, first patented in 1830.