ESP resolved this complexity issue by developing a design that spread the deformation at the top of the wall in the centre of the rhyne, where its maximum retained height was, into either side where the wall was fully embedded. This was achieved through stiffening the walkway such that it could be employed as a whaling beam. This helped to reduce the overall predicted deformation from about 200mm at the top of the wall to less than 50mm without the need to drive additional piles or increase their overall length.
Our recent involvement in drainage improvements works on the Somerset Levels has provided us with some disproportionally complex problems to surmount.
The various drainage boards around the country deal with some pretty difficult ground conditions and still employ some age-old solutions. In a recent project on the Somerset Levels ESP were commissioned to design and detail a minor flow control structure. It comprised of a tilting weir mounted in a sheet pile wall spanning an existing rhyne* with an access walkway along the top. The head of water being ‘retained’ was less than 1m, so where is the complexity?
The complexity came in the form of the ground conditions at the site; which can be summarised as 8m of peat over Mercia Mudstone. This means the wall, when loaded, pushes against a very compressible ‘wet sponge’. Given the wall cannot be allowed to rotate such that it impedes the safe working of the tilting weir this meant the problem became one of serviceability and limiting movement to within acceptable limits.
- Geoenvironmental Investigation