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GNR 1900 Nottingham Extension
GREAT NORTHERN RAILWAY NEW RAILWAY AT NOTTINGHAM.(1900)
By R. F. Bennett, Construction Department, G.N.R.
Some important works have been recently completed by the Great Northern Railway Company at Nottingham, by Mr. A. Ross, M. Inst. C.E., chief engineer to the company, a description of which will probably interest our readers. In the year 1892 the Great Central Railway Company then the Manchester, Sheffield, and Lincolnshire Railway Company applied to Parliament for powers to make an extension of its line from Annesley to London, running through the heart of Nottingham, where they proposed to place a station in the centre of the town.
The Great Northern Railway Company opposed this new route to London, and the bill was thrown out; but in the year 1893, on a second application, it was made with success, the Great Northern Railway withdrawing its opposition after obtaining certain concessions as to running powers, etc., and the option of becoming joint owners of the proposed new central stations at Nottingham and Leicester. It decided only to exercise this right in the case of Nottingham. To obtain access to this joint station it became necessary to construct a short connecting line at Nottingham, from its own Grantham and Nottingham line, to join up with the Great Central Railway at Weekday Cross. As this connecting line passed largely through a populous part of Nottingham, it was necessarily lie expensive, as all railway engineers know the great cost of a railway undertaking passing through any of our large manufacturing towns. To complete the route the Great Northern Railway had also to make connections between their line and the Great Central, north of the town, but we propose to confine our attention to the work at the south end.
It was at first decided that the new line should commence at Meadow-lane, about half a mile cast of Nottingham existing station, pass through the goods yard, and sweeping round to the north, join the Great Central at Weekday Cross. Powers were obtained for this in the year 1895. How- ever, 011 looking further into the matter, the company decided that it could not give up the sidings in the goods yard, and powers were obtained in the year 1897 for a deviation along- side the Nottingham and Grantham Canal, which, fortunately, belonged to the company; the necessary land heiug obtained by narrowing the canal. This alteration involved considerably heavier works, and necessitated interference with the Sneinton Hermitage, an important thoroughfare, which had to lie diverted and widened. The map on page 171 shows the route finally decided upon. The new connecting line starts by a junction with the Nottingham and Grantham line of the Great Northern Railway, close to Trent-lane where the London and North-Western railway goods line joins in, thence it passes Sneinton Hermitage, and skirting the canal, has to pass over a large triangular Canal basin by a large span bridge, then over London-road, and again running along the towing path, it crosses the canal a second time, with a curve of 15 chains radius, and passing over Leen Side, Popham-street, Malt Mill-lane, and Narrow Marsh by bridges, it joins the Great Central railway at Weekday Cross.
The line is constructed throughout as a double line of way, of a first-class character. It was decided that a station should be situated as near the old station at London-road as possible, so as to give access to the large district known as the Meadows. The first part of the line consists of earth- work between retaining walls, then comes a brick arch viaduct of 18 spans, called the Goods Yard Viaduct; and after another short length of earthwork the line runs on to another viaduct, upon which it is carried for the remainder of the distance. The viaducts arc of varied construction, and consist of arches of various heights, of about 30ft. span, mostly on the square. There is also a length of steel viaduct over the sidings next the gasworks, which is carried on steel stanchions, and consists of 19 spans. There are also three lattice girder bridges of large span, and five other bridges of lesser importance.
Before any work was actually commenced, ten bore holes were driven to ascertain the nature of the soil, and it was found that the rock occurred at a depth varying from 13ft. to 30ft.
It is presumed that the route of the new line for a portion of the way was on the old course of the river Trent.
Before reaching the rock, gravel of a varying thickness occurred. Above the gravel to the surface of the ground were layers of clay, sand, and shale, and, on top of all, made ground. As an illustration, the results of three trial holes are given.
No. 1, at the junction with the Grantham and Nottingham line: 3ft. of made ground, 2ft. of soft clay, 1ft. of dirty gravel, 7ft. of clean gravel, giving a total depth of 13ft. Sandstone rock.
No. 10, practically at the centre of the line: 4ft. 9in. of made ground, 5ft. 10in. of mud, peaty clay, and silt, 5ft. 8in. of gravel, 3ft. 6in. of sharp sand, 1ft. 9in. of loose sand, 2ft. of hard red sand. Total depth of 23ft. 6in. Sandstone rock.
No. 7, at the end of the line : 12ft. of made ground and black muddy sand, 8ft. of soft, dirty sand, 4ft. of soft clay, 4ft, of soft, dirty sand, 6ft. of clean gravel. Total depth of 29ft. Sandstone rock.
From the foregoing it will be seen that considerable care had to be exercised in the foundations, and in all cases they were taken down to the gravel, but where cylinders were employed they were taken down to the sandstone rock. A sound gravel foundation was reached at varying depths; and in all cases a large bed of concrete was deposited thereon, the thickness varying from 3ft. to 13ft. The worst foundation was in the neighbourhood of Narrow Marsh, at the northern end of the contract; here the gravel was not reached till 23ft. had been excavated. The water was very troublesome, and it took two 5in. centrifugal pumps working night and day to sump hole, so that the water could get away without taking the cement from the concrete.
At Sneinton Hermitage, an important thoroughfare at the commencement of the railway, had to be diverted, and a new wide roadway formed. The old road was extremely narrow at places, and the company agreed with the Corporation that the new road should be 50ft. in width.
This part of the work was very interesting, as Sneinton Hermitage was probably the oldest part of Nottingham. It passes at the foot of a cliff, which was honeycombed with old cave dwellings of pre historic date. These caves were lived in up to the present day, the same families having occupied them from time immemorial. The caves were in the new red sandstone; they were perfectly dry, and the rooms were unlined, being simply whitewashed. The fronts were bricked up, and the usual doors and windows inserted. The flues from the fireplaces were led out and up the front of the cliff. In one cave was an old chapel with a rude altar; no doubt it was from such a place that the Hermitage got its name. It is asserted that Nottingham itself received its name from these cave dwellings, the Saxon name Snotongaham meaning cave dwellings; this was varied by the Normans to Snotengham, and afterwards to Snottingham. These cave dwellings are shown in Figs. 1, 2, and 3, the last-named being taken after the brick fronts were removed. Many of them had to be destroyed for the road diversion, but a number still remain east of the new works. The road diversion forms a fine thoroughfare. Under it arc some heavy sewer and pipe works, replacing the sewers and mains in the old road. The road abuts against the London and North-Western Railway goods yard on the north side, where a very high retaining wall had to be built. This retaining wall is of no great thickness, as the rock is capable of standing by itself, all it requires being a little facing to keep it from the weather. Fig. 4 shows the rock being cut away for facing. The wall is built of Bulwell stone backed with concrete.
A description in detail of each of the different portions of the work will now be given.
The first road crossed was Meadow-lane, the bridge employed in this case being of the usual type of a centre* and two face girders. The flooring is pressed steel plates filled with asphalt concrete and covered all over with 1 in. of fibrous asphalt, so as to make a watertight job. The asphalt is covered with 3in. of sand, upon which the ordinary ballast is put. The abutments are of the usual type, and arc carried on concrete foundations. The bridge is faced with brindled bricks throughout, and both abutments are built up to retaining walls which support the line on each side.
East and west of Meadow-lane Bridge the line is carried on an embankment supported by retaining walls. The walls arc built of cement concrete faced with brickwork. The system of construction carried out was as follows: - Five courses of l8in. and five courses of 9in. work were built in cement mortar, and allowed three or four days to set; this work was then backed up with cement concrete, which was also allowed to set before more face-work was built.
At the west end of the retaining wall is a viaduct called the Goods Yard Viaduct, consisting of eighteen arches of 27ft. span, with a rise of 10ft. These arches are five rings thick, and are backed up with lime concrete covered with 1in. fibrous asphalt. The water is led to brick cesspits, at the bottom of which are glazed earthenware cisterns, 2ft. 6in. by 1ft. 6in. and 1ft. deep : from these a 4in. east iron outlet pipe is led to the face of the viaduct, and projected over rain- water heads, whence the water is led through a 4in. by 3in. east iron down pipe, connected to a drain running the whole length of the viaduct. The manholes are 8ft. deep by 2ft. 6in. by 1ft. 6in., and have iron steps down, so that if the outlet pipe is stopped up a man can go down to attend to it. The outlet is also made straight, so that rods can be inserted for cleaning the pipe. These cesspits arc shown in the general cross-section, through piers, on page 171. The piers are 4ft. 14in. at top, the sides being battered 1 in 82, but there is no batter at the ends, as it would have made an awkward break at the springing of the arches.
All the piers are built on concrete of varying thickness. The foundations of this portion of the’ viaduct vary considerably in depth. In some eases the rock was reached 8ft. from the surface, and in others the foundations had to be carried down as much as 23ft. The viaduct is built of brickwork in lime mortar, faced with brindled bricks. The parapets arc built in cement mortar, and arc lft.10 1/2 in. thick at bottom, and lft. 6in. above plinths, and are coped with ashlar. Over each pier a refuge 2ft. 6in. wide is constructed and carried on a projection bracketed out from the spandril. The brackets consisted of moulded bricks, and by breaking the straight face line of the viaduct these refuges considerably improve its appearance. As the Goods Yard Viaduct consists of eighteen arches, it was considered too long a range without support, therefore one of the centre openings was bricked up to form a bastion pier, three cross walls being built in the opening. Drawings of parts of the viaducts are given, also a cross section, on page 171.
The next work of importance is that known as the Gasworks Viaduct, commencing with a range of ten arches, eight of which are 28ft. span on square, and two skew spans, the latter having triangular abutments and blind arches. The skew spans were put in to take the large sewers 7ft. 6in. by 5ft., so that they might be examined and repaired without interfering with the viaduct, as they would have done if the piers had been built on top of the sewers. These arches are of the same character as those already described for the Goods Yard Viaduct, and do not call for any special remark, except that the foundations arc unusually deep, ranging from 20ft. to 30ft., the water in all the foundations was very troublesome, as the gravel upon which the lower part of Nottingham rests connects directly with the Trent. When the latter is high the gravel fills with water, and considerable difficulty is experienced in getting foundations in unless there is ample pumping power. By means, however, of laying drain pipes to the sump holes already mentioned, and keeping these sump holes outside the foundations, the water was mastered until the concrete was got in, the system followed being to keep the water running through the pipes till the whole of the concrete was put in, and then letting the water rise. In all cases the concrete was carried up to the level of the water, so that the brickwork was not affected. The timbering was necessarily of a heavy character in the deep trenches, but no trouble was caused by the sides giving way.