The five subsidiary segmental arches, or vaults, run at right angles to the main arches with the small pier walls founded on the main arches and running parallel with the tracks above. These small vaults are not visible externally and are only accessible via a manhole on the Upside of the viaduct, there being one above every main pier. As is described above, to get into these arches is very restrictive and is classed as a 'Confined Space' with specialist examiners required today.
Records show the vaults were only built into the original viaduct (Upside) and not the widened (Downside) section.
These vaults In photograph 'gwrbg1655' you can see the small pier walls. The arches have been removed and the workmen are preparing the walls for the concrete slabs. Photograph 'gwrbg1656' shows the slabs waiting to be installed, due to the angle the photo is taken you cannot see the pier walls in the excavation'. On Bordesley Viaduct the arches are generally seven rings thick, which would be approx. 31.5 inches or 800mm The majority of the piers on Bordesley Viaduct are solid, however some of the larger piers are hollow and have internal vaults to save weight and material. Normally the fill on the arches, may include some clay to try and waterproof the arch, then stone and finally track ballast Drainage from the viaduct is by weep-pipes above each pier, draining into hopper heads and the down the face of the pier to ground level.
Spans of Bordesley Viaduct as numbered from Bordesley Station end
Note. Span 45 is the only steel span in the viaduct.
Much of the information on this and other webpages of Warwickshire Railways is derived from articles or books listed in our 'bibliography'.
Extract from Great Western Magazine Vol. 51. No.11, November 1939
Partial Reconstruction of Bordesley Viaduct Effective Use of Pre-cast Reinforced Concrete Slabs by H. S. B. Whitley.
Bordesley Viaduct is situated on the London side of Snow Hill tunnel and station and carries the railway over a low-lying part of Birmingham, which has for many years been well covered with factories and house property. The report of the Commissioners on the Railway into Birmingham was presented in 1848, and this being ratified by an Act extending the broad gauge from Oxford to Birmingham, the line was opened in 1852. It is not certain that Brunel designed the Bordesley Viaduct, but whoever was responsible evolved a design which is probably unique, although it has been found that under present-day conditions parts of the structure have weakened and renewal work is now being undertaken. The structure is 2,900 feet in length, with a maximum height of 70 feet where it passes over the River Rea.
As originally designed it carried two lines of track, but owing to the great increase in traffic to Birmingham and the North, it became necessary to widen the structure to carry four running lines and one goods loop. The viaduct is built entirely of brickwork and has 60 main arches of an average span of 37 feet with a rise of 18 feet 6 inches. Instead of the voids between them being entirely filled with excavated material, five subsidiary segmental arches were constructed springing from small pier-walls, each having circular openings 18 inches in diameter to enable inspections to be made. These inspections are a very trying ordeal, especially for a tall or broad man. The person carrying out the inspection has to be pushed at one end and pulled at the other, and the work is made more difficult and unpleasant by the interior being wet with slime. More-over, the space between the piers is only 4 foot.
It was these subsidiary arches that began to show weakness, and it was decided to replace them with pre-cast reinforced concrete slabs. The method being adopted is as follows:- Occupation of both up and down main lines is obtained from midnight Saturday until the work is completed on Monday, usually about 6 a.m., and during this period the traffic is worked over the relief lines. To ascertain if the preliminary programme prepared could be carried out within the times laid down, and also to check the estimated cost, Arch No 29 was taken in hand and it was found that no alterations were required. On average 135 men, divided into three shifts are employed during the occupation, and they are provided with two 6-ton steam cranes and the necessary number of trucks to hold temporarily the filling removed, some of which has to be put back after the work of renewing the subsidiary arches has been completed.
As soon as the filling has been removed, together with brickwork in the arches, the tops of the piers are levelled and the reinforcement concrete slabs set in position. As the dimensions vary, however, each type of slab has to be numbered so that each will give the correct bearing. The slabs used were made in the Companys Taunton concrete depot and had loops cast in them to facilitate handling. Having completed the laying of the slabs, the filling is reinstated, together with the ballast and permanent way. Fifty arches are being dealt with as described, and the work on forty-five has been completed; activities were suspended during the summer months, but will proceed at a later date.
An Account of the Works on the Birmingham Extension of the Birmingham and Oxford Junction Railway December 1851
By CHRISTOPHER BAGOT LANE Assoc. Inst. C.E.
The spandrill walls, next the face walls, were built with a batter of 1 in 10 inwards, and two iron tie rods were introduced at the level of the springing of the outside spandrill arches, so as to take the thrust from the face walls. The tie rods were of scrap iron, each 2 inches by 6 inch in section, keyed at each end through iron plates about 10 inches square, one being built into the face wall, and the other being flush with the inner side of the battered spandrill.
Corbels of heading bricks were carried out from the backs of the arches in the range of the spandrill walls, of the same width with them, and connected by a brick beam from arch to arch, for stiffening and equalizing the pressure from end to end of the viaduct.*
* This mode of construction was suggested by something very analogous in Blackfriars Bridge, and its useful effect may be judged of, from the comparatively small amount of the settlement of the arches.
Pieces of hoop iron, each about 3 feet long, were laid diagonally across the bed joints of the arches into which the corbels were bonded; another course of' brickwork was then added, and a second row of hoop iron was laid in the reverse position. Two rows of hoop iron, 12 inches apart, at right angles to each other, were also inserted at the tops of the pillars of the piers.
The settlement of the arches was taken by a spirit-level from three nails, which were driven into each face of the arch before the centres were slacked; ,one of the nails was placed in the crown of the arch, and the two others at 12 feet on each side. The levels were taken before the centres were slacked, and again when the laggings had been for a considerable time quite clear of the soffit.
In addition to the above extract by Christopher Bagot Lane, Graham has provided the following information:
Sadly access to the original 1849 drawings is limited as I believe they were originally held at Railtrack's Birmingham office, were converted to microfiche and now live near York in an impenetrable Network Rail archive. The following is I believe the extent of that collection:
Graham Laucht continues 'thankfully a small number of the original drawings once held by the British Rail Residuary Board reside at Kew though they are now very fragile and access may be limited. Firstly drawing GWR 62714 from the Rail 39/10 bundle at TNA Kew, this is a reduction taken from the original scan which occupies the thick end of 18Mb thus the smaller attachment. I have also attached a smaller scrap showing the detail.
You will see that on the original B&OJ line to Curzon Street Brunel engineered the bridges to be largely hollow structures with the area above the jack arches infilled with excavation rubble and then "layered" over with an 18" thick masonry slab no doubt running between the spandrel walls. There is suggestion in a report by Baggot Lane concerning the original Bordesley construction that wrought iron tie rods also ran across between the spandrel walls though the ends of which may be beneath the outer brick skin as nothing is visible today. Assuming of course that the design of the Bordesley Viaduct was the same on the Birmingham Extension railway to Snow Hill.
It is interesting to note that one of the Rail 39/10 series (GWR 11500) shows the Duddeston viaduct side elevation drawn in pencil beneath the Bordesley elevation which was drawn in ink and wash. Though this collection is small it is very rich in detail particularly of the skewed abutments around Liverpool Street.
In many ways Duddeston was far more varied and interesting in construction particularly as it crossed some pretty difficult terrain enroute to its final frustrated 'destination' just short of the old Curzon Street site. See the schematic diagram below (gwrbg2720) for more infomation'.