FOUNDATION CONTRACTOR Branlow is coping with tight access, a headroom restriction of just 2. 4m and night-time working to install ground anchors for part of the regeneration of Liverpool Lime Street Station.
Branlow, working for main contractor Edmund Nuttall and client Railtrack North West, is installing 20, 610kN anchors for each of three new platform buffers. These are being installed to depths of up to 13. 5m into underlying sandstone, to secure the reinforced concrete buffers so they can safely resist anticipated horizontal forces.
Down-the-hole hammer percussive drilling equipment is being used to form 300mm diameter rock sockets, with 344mm diameter casing employed down to rock head. The anchors comprise a 36mm diameter threaded bar with double corrosion protection and have a fixed length of 6. 5m.
The firm is also forming contiguous mini-piled walls around each of the buffer locations to allow safe excavation for construction. Each consists of 109, 300mm diameter piles, rock-socketed into the underlying sandstone. They are being installed at 400mm centres to an average depth of 6m, again using percussive drilling equipment and temporary casing.
Branlow's Paul Woodfield says access to the site is extremely difficult, involving small but high-powered drill rigs.
'Even the reinforcing cages and anchors had to be installed in short lengths to conform with headroom tolerances, ' he adds.
To minimise disruption to rail services, all work is being carried out at night.