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 t ...
between
Three Bridges and
Balcombe. It is long.
[ The track is electrified with a 750 V DC ]third-rail
A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway ...
.
History
The tunnel was constructed by the London and Brighton Railway between 1838 and 1841, through Grinstead Clay, with five ventilation shafts.[ The engineer for the line was John Urpeth Rastrick; 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 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" ]