The challenge
The full scope of the project has seen the railway line between Wigan and Bolton electrified, along with improvements to the signalling between Lostock Junction and Wigan North Western Station. This includes installing 450 new stanchions for overhead line equipment and lengthening three platforms to address overcrowding at peak times, together with the modification to the 17 bridges and two level crossings.
Appointed by main contractor, Kier, which has been acting on behalf of Network Rail, our work was focused on two bridges: Deep Pit and High Barn. Working with structural engineers, Tony Gee & Partners, and Lead Temporary works designer, DYSE, we supplied our Mass 50 propping, lifting beams, hydraulic jacks and monitoring equipment for the improvements to the historic bridge structures.
Our solution
Billy Darcy, Senior Engineer at Mabey Hire, explained: “Along with other structures along the line, the 150-year-old Grade II listed Deep Pit bridge had to be lifted, providing room for the new overhead line equipment to be installed underneath. This involved raising the 40-metre-long iron truss footbridge 1600mm off its masonry abutments and resting it on temporary supports for six weeks over a live railway. Comprising of a pair of trestles at each end of the structure, our propping scheme enabled us to lift the bridge from above using DYWIDAG hanger system bars and our hollow ram hydraulic double action jacks, all linked to a sync pump.”
“Due to the unique challenges presented, some bespoke fabrications were utilised, including a cradle with skate tracks to help guide the bridge while the lifting bars were threaded through the truss members. This made for quite a complex arrangement involving tapered bearings. We also used our structural monitoring equipment to measure the displacement whilst the jacking was carried out.”
This monitoring took place over a four-week period and included installing biaxial sensors onto each of the props, designed to monitor the degree of movement or lean in the X and Y axis, as well as four laser displacement sensors which were clamped onto the bridge deck itself. These were aimed vertically downwards, recording any movement relative to the ground surface. In both instances, all the measurements were relayed directly to Kier via our Insite web portal, allowing real-time access to the monitoring data and instant alerts should the pre-agreed tolerances be exceeded at any point.
In a second phase just prior to the end of 2024, the 45-tonne Deep Pit footbridge was carefully lowered back onto its re-engineered abutment to rest on new bearings, 1075mm above its original height. In order to minimise disruption to rail users, much of the work was carried out at weekends, with the actual bridge lifts taking place during carefully planned nighttime or extended possessions.
We also supplied Mass 50 propping for the High Barn bridge, with similar works required to allow for the necessary alterations of the bearing shelves on the bridge. This required two sets of 75-tonne hydraulic jacks, due to the 420mm travel being just above the standard stroke of the equipment. Further complicating this task were site constraints, which made it impossible to sink temporary foundations alongside the northern abutment. To work around this, we cooperated closely with structural engineers, Tony Gee & Partners, to design a base which spanned the rail line.
Speaking about the High Barn contract, Billy said: “With one end of the stub beams having to be resin anchored into the masonry structure, we worked with engineers Tony Gee & Partners to come up with an alternative scheme design. After the alterations to the abutments were fully finished, we reversed the jacking process and relocated the deck onto its new bearings at a final height of 390mm above the original position.”
The design manager and consulting engineer for Kier on the project, Paul McGlade, commented: “Both Deep Pit and High Barn were technically challenging bridge jacking projects, each with its own set of unique tasks. Mabey Hire’s design team provided crucial knowledge and equipment to provide bespoke solutions which allowed for speedy installation during the tight timeframes of railway blockades. The 24/7 monitoring solutions were invaluable for real time data, allowing for confidence in how the structure was performing under load while trains were running.”
