Severn-Tunnel

The Severn Tunnel (Welsh: Twnnel Hafren ) is a double-track railway tunnel on the South Wales Main Line at the mouth of the River Severn. It connects South Gloucestershire in the west of England with Monmouthshire in South Wales. It was built from 1873 to 1886 by the Great Western Railway. Its length is a total of 7008 m, of which there are 3620 meters below the river mouth. This makes it the second longest rail tunnel in Britain. Until the opening of the second section of the High Speed ​​One, it was the longest tunnel in Britain.

Planning

Before the construction of the tunnel, the area around Bristol was linked by ferry with South Wales. The railroad was forced to make a long detour via Gloucester, alternatively passengers and cargo could be shipped only consuming. Also in the second half of the 19th century in Wales strongly increasing coal production required new transport routes. The Great Western Railway was planning the construction of the tunnel under "The Shoots ", a rather narrow but also exceptionally low point of the Severn Estuary. This required for railways unusually strong inclination of the ramps to get to the required depth.

Construction

Work on the tunnel began in March 1873 and proceeded in the following years until 1879, has been slow. In October 1879 came on the Welsh side to a large water intrusion ( "the Great Spring "), which due to the geological formation could not be properly closed, and the work in the following years was delayed again and again. When a spring tide on 17 October 1883, already partially completed, but not yet connected to the tunnel entrances were flooded.

Because pumps defects and insufficient pumping capacity of the existing pump was the tunnel or individual segments in the construction phase several times under water. In two incidents, the water penetrated so quickly that the workers existing locks could not close in time. This was accomplished through the use of divers, to limit water entry from the affected segments. In these diving operations called rebreather diving equipment was also first used as the tracking of the usual breathing tubes proved to be problematic because of the length of the route by diving. The puncture for continuous tunnel took place on 17 October 1884.

• 76.4001 million bricks
• 36 794 tonnes of concrete
• 250 tons Tonite ( an explosive )

Completion

The tunnel was completed in 1885 and traveled for the first time on January 9, 1886 by a freight train. The regular operation could be added, which had the pump off at various points, but above all, to the never fully sealed flooding of 1879 constantly trickling water still only after the installation of large pumping stations. In September 1886, the tunnel was finally opened for freight trains from December also for passenger trains. The tunnel reduced the journey time from London to Cardiff for about an hour.

Further development

The original steam-powered pumping stations were replaced until the early 1960s by electrical equipment. These pumps are still daily up to 50,000 cubic meters of water from the tunnel. Freight transport has been greatly reduced due to the closure of most Welsh coal mines, but the tunnel is still an integral part of the British railway network. The low height makes a tunnel electrification with overhead lines difficult, so the important train London - Cardiff - Swansea has to rely on diesel locomotives still, the expansion of the entire route but was announced in July 2009 by the UK Government and is expected no earlier than 2017 ready.