The embankment near the Peel Centre is approximately 7
years old, and has suffered from design and installation issues
The Gabion wall itself is 200 metres in length and 5 metres in
height and a depth at footing level of approximately 4 metres. The
contributory factors to the failure of the wall included:
- Inadequate construction materials
- Incorrect installation of the gabion structure
- Poor use of reclaimed materials within the embankment
Prior to the works commencing, sections of the wall were clearly
noted to be bulging forward with large voids evident in the gabion
USL BridgeCare proposed a bespoke solution to deal
with the issues identified
- Seal the front of the gabion wall using shotcrete
- Injection of grout to fill voids and bind the structure
together utilising the steel mesh present as reinforcement.
- Install weeps holes at the base of the structure to allow the
embankment to drain.
The client requested that USL design a system and method to
ensure 100% void penetration.
Our team submitted plans and method statements that incorporated
a system of 'PRIMARY' and 'SECONDARY' ports. This was ultimately
approved by the clients Engineer. Secondary ports were installed
horizontally to the face of the gabion wall, whilst Primary ports,
used for the injection of grout, were installed vertically through
Initial pre-contract estimates suggested around 15-20% void and
an approximate 550m3, which would require 700 tonnes of
Above: Gabion wall prior to commencement of
Installation of secondary ports - these facilitate the tracking
of the grout flow underground providing a roadmap of progress.
Secondary ports were installed at varying depths ensuring that
ports remained open following shotcrete application. This removed
the need for percussive drilling into the face of the wall during
The gabion wall post shotcrete application - cosmetic finish not
required due to new gabion structure to be placed in front of
USL were able to modify the 2, 3 and 4m primary piling rods on
site to facilitate the injection process - this modification was
made to ensure that piling could be carried out on the embankment
without the need for heavy lifting of percussive piling equipment
above knee level.
Image above shows piling and injection tests at 1 metre back
from the face of the gabion. Once piling is complete design of rods
allows operatives to simply unscrew the piling head from the rod
and attach the injection threads - hi pressure injection hoses are
then attached and injection can begin.