Any railway lineside structure, and any other building for that matter, is only as good as its foundations.
Because they can’t be seen, buried as they are in the ground and usually covered by the structure itself, they can be forgotten.
However, out-of-sight does not make them out-of-mind, particularly when trying to install equipment in tricky locations.
Carillion had just that problem recently when required to install OLE masts along a stretch of the Great Eastern line for Network Rail.
Screw piles seemed to be the way to go, so the project team contacted specialists FLI Structures, members of the Haley Group.
FLI were contracted to design, manufacture and install 20 OLE bases consisting of mast, tie and strut foundations. The project presented FLI with several challenges.
Firstly, most of the foundations were to be installed behind fragile Victorian retaining walls and the brief was to avoid any surcharge on these walls. Secondly, the ground conditions were challenging with a high water table and running sand in some areas.
Thirdly, available space was very limited behind the retaining wall to position the foundations, especially as the foundations had to avoid retaining wall footings, adjacent footpaths and fences.
Finally work was to be carried out in possessions during day / night shifts, in a built up area where noise levels had to be minimised. Screw piling did seem to be the best, and probably the only, solution.
The FLI team designed a range of bespoke screw pile foundation solutions to cater for varying gantry spans and loads. Groups of screw piles were selected, with pile diameters up to 219mm, installed up to 7 metres in depth.
Steel grillages completed the interface between piles and the OLE structures. A large amount of flexibility was built into the steel grillages to allow the site teams to overcome any issues with buried obstructions and services.
This was especially important where bases for an overhead gantry are installed on opposite sides of the rail track as each side has differing physical constraints.
FLI installed the screw piles using RRV’s with torque motor attachments. The installation process was quiet as driven impact hammers were not required, therefore reducing section 61 issues. The retaining walls were unaffected.
As Tony Parker, Sales Manager at FLI, commented, “Our success was based on understanding and solving site problems efficiently, and providing safe solutions for our installers.
“With a strong focus on innovation, we are able to supply foundation solutions to support a wide range of structures in Telecoms, Railway, Highways, Civils and Renewable markets.
“We take experience from each site and use this knowledge to continue to lead the way in the Screw Pile foundations sector.”
FLI’s success on rail sites has been recognised by Network Rail and Birse Rail, who have both presented FLI with their product innovation awards.