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£14.2bn Finland to Estonia undersea mega-tunnel plans unveiled

Staff Writer | February 12, 2018
Initial technical details for the proposed €16bn (£14.2bn), 103km long rail tunnel connecting Finland to Estonia under the Gulf of Finland have been released, which includes two huge artificial islands and a tunnel 250m below sea’s surface.
Finland to Estonia
Transportation   The 103km long rail tunnel
The mega-project will run between the capitals Tallinn and Helsinki at a maximum depth of 250m for the most part through solid crystalline bedrock under the channel, emerging into Estonia through softer sediments of Ediacara and Blue Clay.

To aid construction of the tunnel, FinEst Link said two, 400m x 300m artificial islands, located at places with water depths of 15m and 20m, would be built within the channel using the excavated material from the tunnel construction.

These will provide ventilation, access and energy supplies to the tunnel below.

Under the plans, tunnelling will start from Helsinki using the drill and blast method to the first artificial island, Uppoluoto.

From Uppoluloto access to the tunnel for trucks will be provided by a spiralling 1.5km long, 9m diameter inclined tunnel.

From the second island, Tallinnamatal, due to differing geological conditions, access will be created by two, 215m long vertical shafts to the tunnel below. At the end of both access points, large caves will be constructed and tunnel boring machines (TBMs) assembled.

The TBMs will then be used to bore two, single track, 10m diameter running tunnels about 70m apart with an 8m diameter maintenance tunnel between them. To minimise construction time, six tunnel drives from each island will take place simultaneously.

On completion of the tunnels, the track will be installed and a year of testing will take place before operation is due to start in 2040.