Kaymac were contracted to install a grout mattress protection system to the existing slope on both the East & West Side of the jetty.
During berthing operations at the jetty, propeller action produced highly turbulent water jets which increase the flow velocity at the seabed and cause scour. The loose material of the riverbed and the riverbank behind the submerged piled wall at the Shell Jetty area was found to be considerably eroded from the water jets produced by ships’ main and bow thruster propellers. The slope behind the submerged wall provides support to the existing Thames Flood Defenses at the top of the riverbank, so it was imperative to ensure its protection.
To repair and protect the embankment and foot of the piles from future scour the installation of custom made Proserve fabric mattresses where required.
The existing bed level was littered with debris which needed to be cleared prior to the mattress installation. This was carried out by a combination of land based (at low water periods) and marine plant, with the work being heavily diver orientated.
The location and orientation of the mattresses to be positioned were set out on the slope by Kaymac and guide wires fixed to the submerged pile wall. Once in position, working from Kaymac’s marine plant, divers unrolled the fabric mattress, zipped it around the individual piles and positioned it along the guide wires- with only approximately 1.5hours of dive time being available due to the flow and tidal conditions. Working from the shore, a concrete pump was set up with the tremmie hose end fitted to the inserts of the mattresses by the diver.
Under the control of the diver, micro-concrete was then pumped into the mattress in stages to ensure that the fabric did not burst or damage. Scour repairs were achieved and protected from future damage.