1 Answer

Box Tunnel is a railway tunnel in Western England, between Bath and Chippenham, dug through Box Hill, and is one of the most significant structures on the Great Western Main Line. It was originally built for the Great Western Railway under the direction of the GWR's engineer Isambard Kingdom Brunel.

Engineering drawing of the longitudinal cross-section of Box Tunnel
The tunnel is 1.83 miles (2,937 m) in length, straight, and descends a 1 in 100 gradient from the east. Construction started in 1836, and opened in 1841. The lives of about 100 navvies (railway construction workers) were lost during construction. At the time of opening it was the longest railway tunnel in the world, though the Standedge Tunnel and several other canal tunnels were longer. The dramatic western portal, near Box, is designed in a grand classical style, while the eastern portal, at Corsham, has a more modest brick face with rusticated stone. When the two ends of the tunnel were joined underground there was found to be less than 2 inches (50 mm) error in their alignment.
Box Tunnel is to be electrified with catenary as part of the GWML electrification scheme which includes service to Bristol Temple Meads and is scheduled for completion around 2016.

Read more >http://en.wikipedia.org/wiki/Box_Tunnel