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Kilsby Tunnel
east of Kilsby, Northamptonshire, UK
Kilsby Tunnel
associated engineer
Robert Stephenson
date  May 1835 - 17th September 1838
UK era  Victorian  |  category  Tunnel  |  reference  SP564714
ICE reference number  HEW 55
photo  PHEW
Built as part of the London & Birmingham Railway, Kilsby Tunnel was then by far the longest tunnel for steam locomotives attempted. Serious and unexpected geotechnical problems were encountered during construction, necessitating prolonged pumping, causing delays and additional costs. The tunnel has remained in continual use by main line trains since it opened.
A ridge of high ground between Rugby and Northampton proved a formidable obstacle to the construction of several canals and railways, not least to this tunnel heading south east from Kilsby on the London & Birmingham Railway. Its costly construction delayed the opening of the line — during the works passengers had to complete the journey over the tunnel’s route by stagecoach.
The double track tunnel was designed by Robert Stephenson (1803-59), from 1833 the chief engineer of the London & Birmingham Railway. The 2.2km horseshoe shaped tunnel is unusually high at 8.5m. Stephenson deliberately made it so to help passengers overcome the claustrophobia and fear of suffocation it was expected they would experience while travelling through such a long tunnel.
Trial shafts were sunk, probably in 1834, along the line of the tunnel and revealed lias shale and bands of rock. Few problems were anticipated when construction began in May 1835, but soon afterwards the workers hit quicksand and the tunnel flooded following rock falls from the surrounding oolitic limestone. The site investigation shafts had missed an extensive seam of quicksand (in this case, water-filled sand and gravel) that covered 411m of the tunnel route.
On 12th March 1836, the appointed contractor withdrew from the contract and was replaced by direct labour from the railway company. Stephenson and his father, George Stephenson (1781-1848), visited the site and directed that the water be pumped out of the quicksand. For more than a year, four pumping engines worked almost continuously at 136 litres per second.
The company’s directors sent Captain William Moorsom (1804-63), a soldier and railway engineer, to monitor progress. Despite Moorsom’s favourable reports, they told Stephenson that he had to solve the ground problems within six months or risk cancellation of the project. Stephenson increased the pumping effort — using 13 steam pumps working at 151 litres per second to lift water 45.7m — and successfully dewatered the workings.
The tunnel is lined with brick throughout. The lining was intended to be 457mm thick but was increased to 686mm in most places. The tunnel portals are of limestone ashlar with parabolic arches of dressed stone topped by machiolated cornices, and flanked by brick wing walls.
Access to the tunnel bore was through 25 working shafts, nine of which survive as ventilation shafts. In May 1836, work started on the two huge main shafts (SP569708 and SP574703), situated approximately at the third points of the tunnel’s length. Both are 18.3m in diameter with 910mm thick walls and were built from the top down — one is 40.2m deep and the other 31.1m. Above ground, they are topped by castellated red brick towers. The other seven remaining shafts are much smaller, around 2.5-3m in diameter, and have plain red and blue brick chimneys above ground.
In November 1836, water again burst into the tunnel, unfortunately in an area without pumps, and workmen and materials had to be floated into the tunnel on a raft to complete the brick lining. In March 1838, a seventy yards stretch of tunnel collapsed and had to be repaired.
On 23rd December 1837, the Stephensons and their engineers held a gala dinner at the Dun Cow Inn at Dunchurch, near Rugby, to celebrate completion of the tunnel. Robert Stephenson was presented with a silver soup tureen to mark the occasion. Works trains began using the tunnel in June 1838, and it opened to traffic on 17th September.
A total of 30 million bricks were used, 1 million of them in the largest ventilation shaft alone, and 135,680 cubic metres of soil were excavated. The project was built by a workforce of about 1,300 men, of whom 26 lost their lives during construction. The original contract price was £98,988 but the challenges that had to be overcome pushed the eventual cost to £291,030.
Though the tunnel had been designed for two tracks, at first it had only a single rail line. A policeman stationed at each end of the tunnel signalled the presence of a train to the other, so that only one train entered the tunnel at a time. In June 1852, a fatal collision between a ballast train and a coal train occurred when the signals were either not given or not received. Eventually, in 1879, twin rail tracks were installed.
In March 1987, the north and south tunnel portals were Grade II* listed and the two largest ventilation shafts were Grade II* listed (north shaft) and Grade II listed (south shaft).
On 20th December 2012, Members of the Institution of Mechanical Engineers gathered at the Dun Cow Inn to commemorate the 175th anniversary of the completion of Kilsby Tunnel.
Assistant engineer: Charles Lean
Resident engineers: Frank Forster and G.H. Phipps
Research: ECPK
"The London and Birmingham Railway Companion" by Arthur Freeling, Whittaker & Co., 1838
"The London and Birmingham Railway" by Thomas Roscoe, assisted by Peter Lecount, London, 1839
"Osborne’s London & Birmingham Railway Guide" by E.C. and W. Osborne, Birmingham, 1840
reference sources   CEH E&C

Kilsby Tunnel