Chilterns Railway depot has been cut into a face made up of London Clay – this was originally retained by short, augered soil nails and a weldmesh and ballast-filled facing system.  The existing system has started failing shown by bulging of the face. 

Once Carillion had removed the old facing exposing the weldmesh behind, it became evident that the nails were failing and the weldmesh had ruptured with voids appearing.

CAN was subcontracted in to install more, longer soil nails across the face, with additional nails in the areas that were failing.  One end of the site was only accessible during night time railway possessions.  To expedite the works as quickly as possible a separate day shift and night shift were mobilised.  Following the installation of the soil nails the face was then sprayed with concrete to provide a new hard facing.

Access was the main problem – with all materials and equipment having to be brought to site via RRVs from the Road Rail Access Point which was approximately 800m down the line.  Loading at the RRAP was also an issue as it was the entrance to a busy storage facility.  This meant that loading and unloading had to take place at night.  As the works progressed the designers assessed the face on a regular basis and determined that additional nails were required.

Target dates were hit even with the addition of more soil nails leaving a happy client.

Duration:       4 weeks

Client:            Carillion

Location:       Chiltern Railway Depot, Wembley