Balcombe tunnel is a railway

tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube cons ...

on the

Brighton Main Line The Brighton Main Line (also known as the South Central Main Line) is a major railway line in the United Kingdom that links Brighton, on the south coast of England, with central London. In London the line has two branches, out of and station ...

through the

Sussex Weald The Weald () is an area of South East England between the parallel chalk escarpments of the North and the South Downs. It crosses the counties of Hampshire, Surrey, Sussex and Kent. It has three separate parts: the sandstone "High Weald" in the ...

between Three Bridges and Balcombe. It is long. The track is electrified with a 750 V DC third-rail.

History

The tunnel was constructed by the

London and Brighton Railway The London and Brighton Railway (L&BR) was a railway company in England which was incorporated in 1837 and survived until 1846. Its railway ran from a junction with the London and Croydon Railway (L&CR) at Norwood – which gives it access fro ...

between 1838 and 1841, through

Grinstead Clay The Tunbridge Wells Sand Formation is a geological unit which forms part of the Wealden Group and the uppermost and youngest part of the unofficial Hastings Beds. These geological units make up the core of the geology of the Weald in the English co ...

, with five ventilation shafts. The engineer for the line was

John Urpeth Rastrick John Urpeth Rastrick (26 January 1780 – 1 November 1856) was one of the first English steam locomotive builders. In partnership with James Foster, he formed Foster, Rastrick and Company, the locomotive construction company that built the '' ...

; the contractor responsible for the brick-lined tunnel is not known. Ingress of water from the ground above was experienced during the construction of the tunnel, and this has remained a problem throughout its history. Rastrick described the tunnelling as very treacherous, requiring great caution on the part of the miners working it, as "it swells and effloresces as soon as exposed to the air." Between 1907 and 1909 the tunnel was partially relined with engineering brick.

Galvanised iron Galvanization or galvanizing (American and British English spelling differences, also spelled galvanisation or galvanising) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot ...

sheets were fitted to prevent the water falling on passengers in open carriages, but the blast from the steam locomotives and air pressure created by the passage of trains could result in the metal sheets being torn from the structure, creating a serious hazard. Thereafter drivers were warned about the hazard presented by hanging icicles. The "railway murderer"

Percy Lefroy Mapleton Percy Lefroy Mapleton (also known as Percy Mapleton Lefroy; 23 February 1860 – 29 November 1881) was a British journalist and murderer. He was the British "railway murderer" of 1881. He is important in the history of forensics and policing a ...

left the body of his victim in Balcombe tunnel in 1881. In July 1903 plans were finalised for the boring of a second Balcombe tunnel as part of the scheme to quadruple the

throughout, but these were never implemented. In 1998/9 catchment trays were fitted under the tunnel's ventilation shafts to divert seeping ground water from the shafts into the track drainage system, with a sixth added in 2006/7. The trays consisted of steel decking, gutters and flashings which were installed under limited track possessions. The tray supports had failed by 2013, requiring the installation of additional support brackets, and the

Office of Rail Regulation The Office of Rail and Road (ORR) is a non-ministerial government department responsible for the economic and safety regulation of Britain's railways, and the economic monitoring of National Highways. ORR regulates Network Rail by setting it ...

enforced improvements in tunnel examination procedures. Work is scheduled in October 2018 and February 2019 as part of a £300m improvement programme to stem the leaks, re-lay the track and replace the points.

Views

North portal - see http://www.safeguardeurope.com/case_studies/tunnel_waterproofing_balcombe.php
Aerial view - see http://wikimapia.org/7962596/Balcombe-Tunnel
Junction works timelapse video - see https://www.youtube.com/watch?v=hVsKl3fiquQ

References

{{coord, 51.072131, N, 0.15251, W, type:landmark_region:GB, display=title Railway tunnels in England Tunnels completed in 1841 London, Brighton and South Coast Railway Rail transport in West Sussex Tunnels in West Sussex 1841 establishments in England