Structural Void Filling Behind the Sea Wall at Dovercourt

Background

Sea Wall Failure

The sea defence at Dovercourt, spanning approximately 300 metres, is formed of concrete blocks that have experienced structural failures over time. Persistent water ingress and washout have led to the formation of voids behind the wall, undermining its stability. Despite regular patch repairs, these voids posed a significant risk to the integrity of the sea wall and the surrounding pavement. To ensure the longevity of the defence, a comprehensive solution was required to stabilise the structure by filling the voids effectively.

Challenge

The project faced several challenges:

• The presence of water in the voids, which could affect the performance of conventional repair materials.
• Lack of precise data on the extent of the voids
• Ensure minimal disruption to the site and complete the work within a constrained timeline.

A detailed Ground Penetrating Radar (GPR) survey identified 16 voided locations, each assumed to contain an average volume of 5 cubic metres of backfill loss. This estimation guided the design and material required for the repair works.

Alternatives

Alternative approaches to this issue were considered, however, solutions such as traditional concrete grouting uses a high water content and the curing time is too long for the tidal environment. The site required a fast solution that could be implemented within the tidal window.

Solution

Geobear site delivery team

Geobear’s geopolymer injection technology was identified as the most suitable solution. This method involves the injection of a two-part geopolymer material into the voids. Upon mixing, the material expands and solidifies, filling the voids and providing structural stability. Key features of the solution included:

• Geobear’s geopolymer’s compatibility with marine environments, ensuring it would perform effectively despite water ingress.
• The minimal environmental impact in marine environments, having ESA approval.
• The ability to control injection pressure, minimising the risk of displacing loose blocks.
• A rapid curing process, allowing for efficient completion of works within just four days.

Delivery

The client marked void locations following the GPR survey prior to Geobear’s on-site delivery. Geobear’s team arrived on site with their self-contained injection unit, which included the materials and pump required to complete the works. The team used their custom-built drill stand to drill 16mm holes for the injection tubes. Steel injection tubes were then placed into the holes to allow the material to be injected.

Endoscopic cameras were used to monitor the filling process, ensuring complete coverage of voids without overfilling.

Low Carbon Impact

Geopolymers have been recognised as a low-carbon alternative to traditional cement-based materials, offering up to 80% reduction in carbon emissions compared to conventional concrete, as demonstrated in recent studies. Studies on Geobear’s geopolymer solutions highlight their significantly reduced carbon footprint due to:

• Lower energy requirements during production.
• Reduced material usage owing to the expanding properties of the geopolymer.
• Minimal waste generation, as the injection process is precisely targeted.

In this project, the use of geopolymer injection not only addressed the structural challenges but also aligned with the environmental goals of reducing carbon emissions in construction and maintenance activities.

Outcome

The geopolymer injection successfully stabilised the sea wall at Dovercourt. The work was completed efficiently within the planned four-day timeline, with minimal disruption to the site. The innovative approach ensured long-term stability, mitigating the risks posed by ongoing water ingress and washout. Additionally, the low-carbon credentials of the geopolymer solution contributed to the council’s sustainability objectives.

This project demonstrates the effectiveness of Geobear’s geopolymer technology in addressing complex infrastructure challenges while prioritising environmental sustainability.