Upotustunnelit

Upotustunnelit, also known as immersed tunnels, are a method of constructing tunnels, particularly underwater. This technique involves prefabricating tunnel sections in a dry dock or on land. Once completed, these sections are floated out to sea and submerged into a prepared trench on the seabed. The sections are then joined together underwater to form the continuous tunnel.

The process typically begins with the excavation of a trench along the planned tunnel route. Meanwhile, the tunnel segments are constructed, often in specialized yards. These segments are usually watertight, cylindrical, or box-shaped, made from reinforced concrete or steel. After transport to the site, the segments are carefully sunk into the trench using ballast or controlled flooding. Once in position, they are connected to each other, with methods like rubber gaskets and concrete sealing used to ensure watertight integrity. Finally, the trench is backfilled to secure the tunnel and restore the seabed.

Immersed tunnels are often favored for crossing wide bodies of water, deep channels, or areas where traditional tunneling methods like boring might be impractical or too costly. They can offer advantages in terms of construction speed and predictability compared to some other tunneling techniques. Famous examples of immersed tunnels include the Marmaray Tunnel in Istanbul and the Hong Kong-Zhuhai-Macau Bridge's tunnel section. The design and construction require careful consideration of buoyancy, hydrodynamics, and the long-term stability of the seabed.