Swanage is a coastal town in the South West of England. Geobear was contacted by Dorset County Council to deliver a solution to fill voids adjacent to the town’s historic seafront wall.
Following a condition assessment carried out by WSP, whereby a visual inspection was supplemented by a geophysical survey, areas of potential voiding were identified.
The stone sea retaining wall is a listed structure and there are various historic structures on the surface and sub-surface that include tram tracks and timber sleepers that could not be disturbed. This meant further intrusive ground investigation
work could not be conducted and they needed to find a suitable method to fill the voids.
In total there were five areas identified that required void filling, Geobear were approached by Dorset CC to propose a solution.
The listed site, and its use by the local community, meant any remedial works would need to be non-disruptive to the local area whilst minimising any excessive damage through invasive methods. This ruled out many of the traditional techniques such as breaking out and filling with concrete or a pumped foamcrete.
The solution we proposed would utilise the Geobear geopolymer injection method using a water resistant, lightweight fill material. A detailed ground penetrating radar survey pinpointed the areas that were voided and required filling. Our method would see us drill through the walkway above the retaining wall and inject expansive geopolymer material into the voided areas.
Our geopolymer material was injected via 12mm tubes as a liquid which then expanded into the voided areas filling and compacting the locations. We drilled to the identified depths of the voids and injected a specified amount of geopolymer material. In total we injected 2.4 tonnes of geopolymer across the sea front. Laser monitoring was used to ensure there was no structural movement as our material expanded.
This preventive maintenance will ensure there are no unforeseen collapses on the seafront which is a busy pedestrian route for locals and tourists. The works were undertaken over a three day period and the areas were opened back up to pedestrians after each shift.