Underwater tunnel

An underwater tunnel is an engineered passage beneath a body of water, carrying transport or utilities between shores or other locations.

Immersed tube tunnel: A tunnel assembled from prefabricated sections sunk into a dredged trench and joined underwater. This construction method creates many underwater road and rail crossings.
Hydrostatic pressure: The pressure exerted by a fluid at rest, increasing with depth. It loads the tunnel lining and makes watertight joints essential.
Channel Tunnel: A rail tunnel linking Folkestone in England with Coquelles near Calais in France beneath the English Channel. It is a major bored tunnel beneath a busy international waterway.
Bridge: A structure that carries a route over an obstacle such as water, a valley, or another road. A bridge crosses above water, while an underwater tunnel passes beneath it.
Tunnel-induced settlement: Ground subsidence caused by excavation, dewatering, or changes in underground support. Settlement near approaches can damage buildings and infrastructure.
Tunnel boring machine: A machine that excavates tunnels through soil or rock while supporting the surrounding ground. Bored underwater tunnels use these machines to advance below the seabed.
Groundwater control: Engineering methods for limiting or managing water flowing through soil and rock. Construction must control seepage around the excavation and its approaches.
Seikan Tunnel: A railway tunnel connecting the Japanese islands of Honshu and Hokkaido beneath the Tsugaru Strait. Its deep, long route demonstrates the demands of a strait crossing.
Submerged floating tunnel: A proposed tunnel held below the water surface by buoyancy and anchored or tethered in place. Unlike a seabed tunnel, it would be suspended within the water column.
Environmental impact assessment: A process for identifying and evaluating the environmental effects of a proposed project. Dredging and construction can disturb aquatic habitats and sediment.

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