How was the first underwater tunnel built?

Brunel and Cochrane used a similar method to finish the Thames Tunnel. Miners would dig at the front of the tunnel, protected by a movable wooden framework. Immediately behind the miners, workers would secure the tunnel, covering the walls with bricks and concrete. The tunneling shield method is still in use today.



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The first underwater tunnel opened 175 years ago, on March 25th, 1843, under the Thames in London, then the world's largest city. An engineering marvel, the Thames Tunnel saw some 24 million pedestrians pass through before it was converted to rail use for the Underground in 1865.

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Drainage systems: Tunnels have an extensive network of drainage systems in place. This includes channels, pipes, and pumps that collect and redirect rainwater away from the tunnel. The drainage systems are designed to handle the anticipated volume of water during heavy rainfall events.

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Because they're stronger that way. Tunnels are circular to take advantage of the characteristics of soil and rock. Soil and rock are resistant to crushing forces (compressive forces). By rounding the ceiling, the weight of the soil and rock from the top to are balanced over the entire tunnel, increasing its strength.

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Because we dig while reinforcing them. Once a tunnel is dug, the walls are sprayed with concrete and immediately hardened. Also, steel frames called steel support and steel rods called rock bolts are used to reinforce the tunnel so that it can be dug without collapsing.

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The main channel measures 3,700 feet between the 6-fathom lines, with at least 58 feet of water required over the tunnel backfill for a distance of 3, 170 feet. The maximum natural depth of the channel reaches close to 70 feet.

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“The first infrastructures of this type were built at the end of the 19th century, and at present there are nearly 200 underwater tunnels built worldwide. Although some are used for water and electricity supply, most are used to house road or rail connections.

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The world's longest underway highway tunnel is Norway's 14.3-kilometer twin-road Ryfast tunnel, which runs between the city of Stavanger and the municipality of Strand. The underwater tunnel portion of the Tokyo Bay Aqua-Line, a vehicle highway that travels under Tokyo Bay, is 9.6 kilometers.

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Given that many tunnels are below ground, they have long been designed and built to be watertight and with features that provide flood defence. Anti flooding measures include drainage systems, pumps, waterproofing of walls and ceilings, and increasingly sophisticated flood warning systems.

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