Temporary Works for the Keighley & Worth Valley Railway Bridge 27 Project
The Keighley & Worth Valley Railway is a 4 ½ mile long heritage railway in West Yorkshire, running from Keighley to Oxenhope via Haworth. To the south of Haworth, the single-track branch line crosses the Bridgehouse Beck watercourse on Bridge 27. Maintenance work on the line is typically undertaken by a team of volunteers; however, the 150-year-old western span of Bridge 27 had deteriorated and required urgent replacement, a task which required the involvement of specialist contractors to supplement the volunteer workforce.
Cass Hayward were appointed as a Designer for the scheme and provided a design for a single-span prefabricated steel bridge supported on piled abutments, allowing demolition of the existing 1870s bridge and improving water flow in Bridgehouse Beck by removing the need for a central pier. The bridge deck was fabricated and prepared for installation by Beaver Bridges Ltd to be supported on piles installed by Keller Piling.
Pell Frischmann were appointed as the temporary works Designer for the geotechnical aspects of the scheme. Our scope was initially to design a temporary works platform for use during the piling phase of the works, this platform comprised a basal biaxial geogrid overlain by compacted Class 6F5 granular material to create a safe level working area for the piling rig. The Class 6F5 was specifically chosen due to its availability from a nearby quarry, helping to lower the environmental impact of the scheme and reducing the need for HGV movements on the narrow local roads.
Following positive feedback on the piling mattress design Pell Frischmann were also asked to assess the bearing capacity of the ground beneath the mobile crane outrigger pads ahead of the planned bridge deck lift. This latter task was complicated by the constrained site; with the only available area for the lift being adjacent to the Wyedean Weaving Company in an area presently used as a car park but historically occupied by mill buildings and infrastructure. A ground investigation revealed variable thicknesses of Made Ground throughout the site and the PAS128 utilities survey identified a combined water sewer at 2.2m depth beneath the position of one of the crane outrigger pads. With no alternative position for the crane during the lift, a settlement analysis of the sewer was undertaken that determined negligible settlement along the crown of the sewer, allowing the lift to go ahead.
The bridge deck lift was successfully carried out on 14th September by Ainscough Ltd. Approximately 2mm of reflective settlement was reported within the tarmac car park surfacing beneath the outrigger pads following the lift, a value that was within the expected settlement range and easily remediated before handback of the lift area to the landowner.
Work to finish the bridge and reinstate the trackwork was undertaken during the following week; during this latter work, we were told that the now-redundant piling mattress we had previously designed had the unintended bonus of creating stable sidewalls to the excavations required for formwork on the bridge abutments. The first train crossed the reconstructed bridge on 21st September and Pell Frischmann were invited to the reopening celebrations, a testament to the service we provided to our client.
