Hard revetment works to prevent erosion in a river channel
This project was to bolster the existing erosion control measures downstream of the major weir structure controlling flow from the River Thames down the Jubilee River.
The Jubilee river was constructed in the later part of the 1990ʼs as part of a flood alleviation scheme for Eton, Windsor and Maidenhead. Since it was commissioned it has been tested a few times with major flood events and required some ongoing maintenance to the banks immediately downstream of the tilting weirs.
On the left bank we were to add to the existing rip rap(rock armour) protection at the downstream extent where the flows had found a weak spot and the bank was eroding.
This work was carried out using a modular floating pontoon to transport the rock across the river from the site compound above the right bank to the left bank. The rock was loaded onto the pontoon using a long reach excavator and then placed by a smaller 8 tonne machine located on the pontoon.
The pontoon sections were craned in from the bridge above and assembled in the channel before 8 tonne excavator was craned down onto it. Timber bogmats were then placed over the pontoon to protect the decks. The pontoon is manoeuvred into position using a work boat.
On completion of the rock placement works began on the right bank where the existing interlocking concrete block revetment required extending up the bank adjacent to some existing stone filled gabion baskets where the water in high flows had found another weak spot.
It was not possible to link the new concrete blocks to the existing ones and so a row of interlocking trench sheets was driven along the top edge of the existing ones to act as a toe (base) for the new blocks and prevent them moving.
The gap between the two sets of blocks was filled with mass concrete. Ballast was then imported to fill the eroded area and form a level surface to lay the new blocks on.
Once laid the new interlocking armorloc blocks are blinded with ballast to lock them together in place.
