This project was a cess retention and soil nailing scheme to stabilise both sides of a 140m length of rail embankment with the installation of over 1100 soil nails and a Deltax facing system. During the installation of the soil nails, CAN used their Network Rail approved slew restricted long reach and 22T excavators.
These machines were also utilised to install a cess retention system running along the entire length of the site, which consisted of an ARMCO barrier secured to Grundomat piles and then backfilled. Once installed, this created a wider cess which then had an additional Kee Clamp hand railing system installed.
Undermining the toe of the embankment of the South Side meant this specific area located nearby a river, posed a particular problem. The design solution chosen, combined the installation of a soil nail reinforced scour protection system, including rock rolls and mattresses. Very tight access prohibited the use of traditional plant. The initial plan was to use crane lifts to carry out the works during possession. This meant undertaking these works at night and during possessions.
To avoid this, CAN designed a completely different method of working, carrying out the works during normal daytime working and without the need for any possession work.
Initially, using slop mounted drill rigs meant that the soil nails could be installed and then partnering with Salix to use one of their spider excavators, meant that the scour protection could be installed from within the river itself. The new solution included bio oils and slit traps/surface booms in place downstream. Carrying out the works efficiently was a result of this new solution, in an environmentally safe manner and during normal train running hours without the need for possessions.
The rock netting facing system was extended following the installation of the rock rolls and mattresses. It continued over the top of the scour protection and was secured with head plates to the soil nails, which were previously installed to provide a robust long term solution. Applying top soil and a river bank seed mix over the whole area helped to encourage regrowth.
Completing the works within budget was a result of using the above plant and access methods and, more importantly, over a significantly reduced programme duration.
Duration: 5 Months
Client: Balfour Beatty
Location: Trowbridge, Wiltshire