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LMS Route: Evesham to Birmingham

Cofton Farm Station Cofton Tunnel

Cofton Tunnel

Description of Tunnel

Cofton Tunnel, which was situated about seven miles south of Birmingham on the Derby and Bristol main line, was built in 1838-1841 as part of the Birmingham and Gloucester Railway. It was 440 yards long, and had a span of 23 feet, and a height at the centre from rail level of 17 feet 2 inches. The tunnel, which was not inverted, was built of red brick in lime mortar. In section it consisted of a segmental arch with curved side walls, springing level being 8 feet 10 inches above rail level. The side walls were built in Old English Bond, and are 2 feet thick laid to a radius of 15 feet. The arch was built in separate 4½ inch rings, with no bonders between the rings, and varied from 1 foot 6 inches to 2 feet 3 inches in thickness, that is from 4 to 5 and 6 rings. The radius of the inner ring was 11 feet 0 inches. For purposes of construction eight shafts were sunk, of which three were lined with brickwork, and kept open for ventilating purposes, the other five being sealed at the 'eve' and filled in. The first six shafts from the north end of the tunnel were nine feet in diameter, the other two being seven feet in diameter. The 'eye' of each shaft in the tunnel arch was formed by a cast iron flanged curb, consisting of four segments bolted together and weighing approximately 3 tons. The depth of the curbs was 1 foot 9 inches, and they were shaped so as to conform to the curvature of the arch, the outer edges of the curbs being radial to the arch at all points.

During the period that elapsed since the time of construction practically the whole of the original inner ring has been cut out in patches, and replaced with blue brickwork either in lime or cement mortar, as a matter of ordinary maintenance. In carrying out this maintenance repair to the side walls the front half of every header brick in the original facing work was cut off, and the replacing blue brickwork laid all as stretchers. No accurate records are available of the dates of such repairs, but the most recent appear to have been over 20 years ago. Generally speaking the brickwork, both original and repaired, was in a sound condition, and the regular and detailed examinations, of which the most recent were in January, 1928. and on May 6th, indicated no serious deterioration on the visible surfaces. The tunnel was damp in parts and after the failure some of the brickwork behind the lining was found to lie in inferior condition, probably largely due to damp. It was not, however, what would be described as an exceptionally wet tunnel. In 1922 a scheme was prepared for widening about 2½ miles of this line between Longbridge and Burnt Green, which included the tunnel, by the addition of two new lines on the Eastern or down side. The tunnel was too tight in gauge to permit the use of modern wide carriage stock, and as the height of the ground above rail level was only about 70 feet it was decided to open out the tunnel and accommodate both the existing and new lines in an open cutting.

In September 1925, a contract for the construction of this widening was let to Logan & Hemingway, Contractors, of Doncaster, and in March, 1926, excavation in the cutting was commenced near the south face of the tunnel. All work carried out by the Contractors was under the instructions of the LMS Company's Engineering staff, and the work was supervised by the LMS Company's Resident Engineer. The Contractors and the LMS Company's Engineering Staff were in agreement as to the suitability of the methods adopted. Careful and elaborate arrangements were made lo safeguard traffic on the line, by the provision of a temporary signal box, special automatic alarm communications. flagmen, speed restrictions, etc., together with continuous patrolling and examination of the tunnel. The material above, which consisted of sandstone and beds of hard marl, was removed in successively lower lifts, and while this excavation was in progress a slip occurred on the west side of the cutting, and to deal with this and other slips threatening on that side, it was decided to construct a heavy concrete retaining wall. This wall was commenced in January, 1927, and was constructed in trench, in alternate lengths 24 feet long by 15 feet wide, and when finished in December, 1927, was 310 yards long, commencing at approximately the north end of the tunnel, and running south alongside the tunnel. The foot of this wall was some 4 feet clear of the outer surface of the tunnel side wall. During this period the cutting over the tunnel was excavated to a general level of 12 feet above the tunnel arch, and on the east side of the tunnel to a level approximately the same as the springing level of the arch, leaving a minimum thickness at the side of the tunnel arch of 12 feet.

Arrangements for Demolition

In November, 1927, the method of excavating the remaining material round the tunnel and removing the tunnel itself was discussed and a scheme in six stages was adopted. The first three of these stages included the removal of the material above and at the sides of the arch down to approximately springing level, and the fourth stage was the actual dropping and removal of the arch masonry itself. It was decided that this work should be carried out by dividing the tunnel into lengths of about 50 feet by cutting chases through the brickwork across the arch from springing to springing, and that windows should he cut through the haunches at springing level on both sides during the week days prior to the Sundays fixed for demolition, the final dropping being effected by small charges of ammonal in the pillars remaining between the windows. During all the later stages suitable precautions were taken to ensure that steam navvies and cranes should only work at a safe distance from the tunnel and similarly that no blasting should be allowed within 12 feet of the tunnel.

At the end of April, 1028, it was decided that a length of 400 feet at the northern end of the tunnel should be dropped on Sunday, May 13th, and it was arranged in conference with the traffic officers concerned that on that date the Engineers should have complete occupation of both lines for three periods of about four hours each, and occupation of the down line only throughout the day. On Monday, May 7th, the cutting of the chases and windows was started on this length. When the chases were marked out it was found that the southernmost one would come very close to one of the 9 feet diameter cast iron curbs of the old shafts, and the southernmost length (No. 8) was therefore extended to 60 feet in order that the chase should be well clear of this. The windows at springing level in the haunches were each about 4 feet long by 2 feet 6 inches high, and spaced so as to leave pillars about 3 feet wide between the windows. A light timber strutting was placed in each window in order to prevent the brickwork in the top of the window from falling, but this strutting was not intended to, and in fact could not, give any appreciable assistance to the pillars in supporting the main body of brickwork of the tunnel arch.

The procedure adopted was that the red brick main outer thickness of each window was cut away by men working pneumatic hammers; the light timber strutting was then put in place, and finally the blue brick inner skin of the tunnel was cut through by pneumatic hammers. During the latter work, men were employed in the tunnel below to remove any broken brickwork which fell inside. Throughout the cutting of chases and windows the brickwork revealed by the. cuts was found to be sound and in good condition, the latest inspection being made on the Friday morning by the LMS. Resident Engineer who examined chases and windows from outside and inside, and was satisfied as to the condition of the brickwork therein.

Colonel AC Trench. 5th July 1928

The remainder of Colonel Trench's report addressing the conditions immediately prior to the accident which occurred on Friday 11th May 1928, the reasons for the accident and what should have been done instead can be read in his report given in the PDF document at the bottom of this page. Courtesy of www.railwaysarchive.co.uk

The entrance to Cofton tunnel can be seen beneath the early stages of the cutting being widening in the summer of 1928
Ref: mrcof1669
JA Penden
The entrance to Cofton tunnel can be seen beneath the early stages of the widening of the cutting in 1928
The demolition and widening of Cofton Tunnel can be seen to be in progressing well in April 1928
Ref: mrcof1666
D Powell
The demolition and widening of Cofton Tunnel can be seen to be in progressing well in April 1928
Three of Logan and Hemingway's rail mounted steam powered cranes are working to clear the rubble over the weekend of 26th to 18th January 1929
Ref: mrcof1671
JA Penden
Three of Logan and Hemingway's rail mounted steam powered cranes are working to clear the rubble
An unidentified ex-MR 0-6-0T is seen running bunker first through Cofton Cutting in the summer of 1929
Ref: mrcof1667
RS Carpenter
An unidentified ex-MR 0-6-0T is seen running bunker first through Cofton Cutting in the summer of 1929
An unidentified ex-MR 3F 0-6-0 locomotive and an LMS 4F 0-6-0 locomotive are being employed on works trains
Ref: mrcof1668
JA Penden
An ex-MR 3F 0-6-0 locomotive and an LMS 4F 0-6-0 locomotive are being employed on works trains

Logan and Hemingway's 0-6-0ST No 5, built by Manning Wardle of Hunslet Leeds as Works No 1795
Ref: mrcof1670
JA Penden
Logan and Hemingway's 0-6-0ST No 5, built by Manning Wardle of Hunslet Leeds as Works No 1795

Minutes of the Proceedings of the Institution of Civil Engineers

16 December, 1930. President, in the Chair, Sir GEORGE WILLIAM HUMPHREYS, K.B.E.

The Opening-Out of Cofton Tunnel, London Midland and Scottish Kailway.
By Robert Towson McCallum, O.B.E., B.Sc., B.Sc. (Eng.), M. Inst. C.E.

Abridged. (Paper No 4773)

The work described in this Paper comprised the removal of an old and 'tight' double main-line tunnel and making the open cutting so formed wide enough to take two additional lines. Two features made it a more than usually interesting example of tunnel-demolition. Firstly, it became evident soon after the excavation over the tunnel had been begun that the ground was folded and much faulted, and as the depth of the cutting was increased serious troubles were experienced with slips, associated with these faults, in the new slopes. These, and the threat of further and more serious slips, necessitated costly remedial and preventive works, including the construction in trench of a concrete retaining-wall along the outside of the west side wall of the tunnel throughout its whole length. Secondly, the felling of a length of 265 yards of arch and clearing the debris had to be carried out in one continuous operation. The geological structure of the ground played so important a part in the work that considerable attention was given to it; and an attempt has been made to analyse the conditions causing the various slips which were such an outstanding feature of the excavations. Cofton tunnel was situated about 7 miles south of Birmingham, on a portion of the Derby and Bristol main line of the London Midland and Scottish Railway known as the Birmingham and Gloucester Railway, which was authorized in 1836, and constructed in 1838-1841, the Engineer being Captain WS Moorsom.

Following on Correspondence

Mr HK Beale, of Derby, observed that 25 years ago, or possibly more, he had been engaged upon an inquiry about a footpath across the railway near the Cofton tunnel, and had met, by appointment, a very old ex-ganger who had been employed upon the length in question for many years. He told Mr. Beale that as a boy he had been employed in driving the Kilsby tunnel on the London and Birmingham line ; from there he had been transferred to the Clay Cross tunnel on the North Midland line ; and from there to Cofton. He said that they had worked at Cofton under great pressure in order to get the tunnel through ; that at that time the Birmingham and Gloucester Railway was open and working from Gloucester to near the southern end of the tunnel; and that the last 8 miles between the north end of the tunnel and Birmingham was ready for opening, but not working. He added that passengers had come in and out from Birmingham by coach and had been set down in a field near the south end of the tunnel at a temporary platform. The old man's recollection was very clear on the efforts that were being made to get the tunnel through, as only that short length of the railway had been delaying the completion of the line. His story entirely fitted in with the Author's theory that the engineers had found themselves in very difficult ground and at the last moment had had to substitute a tunnel for an open cutting. It also accounted for there being eight shafts in ¼ mile of tunnel, the only purpose of which could have been to get as many working-faces as possible. They could not have been ventilators in that short length, and as a matter of fact five of them were found to have been filled when the tunnel was being opened out. The events recounted by that old man took place nearly 100 years ago ; but his conversation had left a great impression because he had had such a clear recollection of his earlier experiences in the railway world. He had also told Mr. Beale that, while he was working at Cofton, the Lickey incline, which was about 3 miles south of the tunnel, was worked by engines obtained from America. Mr. Beale did not remember whether he had said that the American engines were used on the opening of the railway or whether he was talking of some slightly later date ; but the old man had evidently actually seen them at work.

Report on the Accident at Cofton Tunnel on 11th May 1928

The report on the collapse of Cofton Tunnel in 1928

A number of men were working in the tunnel under No 8 section, placing sleepers to protect the permanent way in readiness for the Sunday, and clearing away the brickwork knocked in by the workmen outside who were finishing the windows, when the whole of No. 8 section of the tunnel suddenly collapsed on the top of them. One of the men, who was standing at the north end of No. 8 section, suddenly saw light shine through a crack which appeared to open at the Barnt Green (South) end, lying towards the west side of the arch, and which extended to the north end of the section. He had the impression that the crack was near the west side of the curb, and that the west side of the roof fell first. Another man standing below saw dust coming from one of the pillars at the north end on the east side. He shouted a warning and jumped back in time to get clear. Various other men who were working above agreed that the arch collapsed suddenly without any warning. The general impression of those working on the east side was that the arch fell away from them, whereas two men working on the west side had the impression that the arch came towards them like a wave, and they were both knocked over by a quantity of brickwork. Portions of the windows and pillars on the east side were left standing after the collapse.

Schematic showing the location and layout of Signal Boxes No 1 to No 4 at Washwood Heath Sidings
Ref: MoT_CoftonTunnel1928
Railways Archive
Ministry of Transport Report on the Accident at Cofton Tunnel on 11th May 1928 written by Colonel AC Trench