Chris Parker reports
As a keen narrowboater, I often remark upon the great skills of our engineering ancestors. Time and again I find that the canal route I am following has been copied by the builders of a railway and, later, by the highway engineers. It shows how great the abilities of the early engineers must have been when they chose routes that have still to be bettered by their modern successors, despite all our subsequent technological advances.
Reinforced concrete slab
At Medge Hall on the route from Doncaster to Scunthorpe, the railway follows the line of the Stainforth & Keadby Canal, crossing a peat bog in the process. Opened in 1802, the canal has been very happy sitting in its flexible surroundings. Not so the railway however! The peat has always presented problems, the weak substructure causing rapid and serious track deterioration.
Temporary restrictions of speed and even an emergency line closure have been necessary at the site so our ancestors couldn’t always get it quite right! Network Rail has now started to effect a permanent solution with the objective of achieving a reliable speed of 55mph or better. Prior to the start of work, the speed through the site was down to 10mph.
The project involves constructing a 450m long, piled, reinforced concrete slab to carry the rebuilt line over the poor ground. Main contractor Carillon is implementing a detailed design that was produced by Grontmij from an outline design prepared by Scott Wilson Ltd. Track works are being undertaken by Jarvis.
Delivery by canal
An important issue in the planning and execution of the project has been minimising the impacts of the project upon the environment and the railway’s neighbours. Playing a key role in the design has been the choice of piling system. To minimise the noise of pile driving and to reduce the volume of concrete needed to form the piles, tubular steel pile casings – supplied and installed by specialist subcontractor Van Elle – are being used for the 1,250 piles involved. These casings are bottom-driven rather than being struck at their top in the conventional fashion. This technique means that the noise generated by the operation is greatly reduced compared with normal pile driving. However, as can be imagined, 1,250 reinforced concrete piles mean a significant tonnage of steel reinforcement to be delivered to site.
Access to the site was restrictive with narrow lanes, swing bridges and low weight limits on watercourse bridges. In order to deliver materials and heavy plant, agreement was reached with North Lincolnshire Council to use a route through the nearby town of Crowle. Nonetheless, this still involved the upgrading of a 2.7km existing farm track and construction of a further 1.4km of temporary haul road across farmland to reach the site. Once at the site and with the cooperation of the Environment Agency, three temporary vehicle bridges and two temporary footbridges were installed over the North Soak Drain – which runs parallel to the railway – for the delivery of plant, personnel and materials. Water vole habitat found at the bridge sites had to be relocated with the assitance of specialist ecologists.
In order to minimise disruption to the other works on the line and reduce the impact of road traffic in Crowle, the steel reinforcement for the concrete slabs has been delivered by barge on the canal alongside. This has been undertaken on behalf of Carillion by Alan Oliver Workboats of Doncaster who specialise in water-based material delivery and cranage in association with engineering works. The number of lorries has been further reduced by the chosen type of pile, requiring less concrete than conventional versions and therefore resulting in fewer truck mixer journeys.
The 11-week project, with an expected cost of £10 million, began on site on 21st July. The nature of the work means that the line is completely closed to rail traffic and this dictated the timing of the job. Whilst the passenger traffic on the line is relatively unaffected by seasonal factors, the freight flows are significantly reduced over the summer months. Coal traffic from the east coast ports to power stations is down by about 16 trains a day – eight loaded and eight returning empties.
The line is a vital freight artery, carrying about 35 million tonnes of freight per annum so this variation in traffic was a sufficient issue to dictate that the works take place in the summer. The remaining freight, including iron ore and steel as well as the surviving coal trains, is being diverted via the Brigg line which Carillion upgraded for Network Rail in 2008 at a cost of £10 million. Passengers are being taken around the works by bus.
Taking advantage of the main line closure, £4.1 million worth of other works are being carried out along the route including track renewal at Crowle worth £1.1 million. This is in the hands of Jarvis whilst Network Rail’s own staff are dealing with the maintenance work.
During the last nine days of the blockade, another major job will be undertaken. Thorne Junction is to be relaid, costing a further £5.8 million. Once again, the renewal works are to be carried out by Jarvis who will be doing both track and signalling items. Since the junction is the point where the Goole-Doncaster route and the Doncaster-Scunthorpe route diverge, the Goole line will also be closed to trains for the nine days.
As the rail engineer went to press, the main project was on time with Van Elle driving piles at up to 45 per day, despite a run of bad weather in July. A significant length of the reinforced concrete track support slab had also been cast. The slab construction is being carried out in 13 sections – the supporting piles being in five parallel rows, each row having piles at 2.25m centres. The piling was finished in July and the whole work was due to be completed and everything reopened to normal traffic on 7th September. In all, £20 million is expected to have been invested by Network Rail by this date, making some very significant improvements to this important rail artery.
Article courtesy of the rail engineer magazine.