The existing tidal structure located at Cake Pill in Aust, Somerset was suffering from a severe case of scour under the reinforced concrete outfall slab. This had caused the tidal water to seep up underneath the structure and burst the joints between the precast concrete culvert sections, whilst eroding the backfill material around the culvert units.
MDA completed these refurbishment works by firstly excavating in front of the outlet slab and removing the silt, then forming a reinforce concreate toe beam embedded into the bedrock below. This wall then filled with 40tonnes of 300-500mm granite rock armour to protect the structure and surrounding wing-walls.
Once the curtain wall was formed at the outlet end, a series of 50mm diameter core holes were drill through the structure at 1m centres and grout was pressure pumped into these holes systematically from inlet to outlet to fill any voids around the structure. This process could be easily monitored by drilling air holes ahead of the grout holes to check that the structure was being fill up evenly.