WORKING FROM above and with the pile line only 2.5m from a running rail, Stent Foundations has its work cut out during stabilisation of a cutting in Crewe.
The Crewe Salop railway runs behind Crewe Alexandra Football Club and Rail House in a 250m long, 9m deep cutting which had failed along its entire length.
Tension cracks had damaged the Rail House car park and threatened sensitive buildings and services at the slope crest.
Heave to the toe of the slope had also affected the track requiring urgent remediation.
A ground investigation by Scott Wilson Kirkpatrick, appointed to design the remedial works, revealed fill and glacial till over soft laminated clays with large, deep-seated slip surfaces and more localised shallow instability.
A sheet pile toe retaining wall comprising 12m to 14m long sheet piles, with coarse granular backfill is being built to stabilise both slip mechanisms.
The £3.5M package is being managed by Edmund Nuttall and funded by Railtrack as part of the Structures Alliance works in this part of England.
Selection of the correct cranage and plant was crucial for Stent.
Daily isolation of the nearest running line catenary and temporary possessions enabled it to use a 100t crawler crane with slew restrictor, sat on the top of the embankment and working at about 30° to the rail tracks.
Piles were pitched using a 2316VM resonance free vibro hammer and driven to final level with a Dawson HPH2400 hydraulic drop hammer. Vibration monitored during the initial installation was within limits set to ensure no further slippage.
An access ramp was built after the first 80m of sheet pile wall had been completed, allowing a 40t crawler crane to work from an access road behind the piles.
This in turn allowed work to progress behind the football club and Rail House.
Stent also installed 14m long piles beneath a 10m high overhead service gantry with rigs having to cross three fibre optic cables controlling signalling for the West Coast Main Line.
Nuttall is now excavating the fill and step profiling the glacial till to allow the engineering backfill to be completed. Graded stone fill is used to reform the embankment profile, capped with topsoil to allow seeding.