Dual Carriageway Ground Improvement Scheme

Background

The dual carriageway of a primary A road connecting London to the north experienced significant deterioration due to underlying soil instability. This resulted in extensive cracking and potholes, despite multiple resurfacing efforts. Investigations revealed that voids and subsidence beneath the rigid road compromised its structural integrity. Geobear was engaged to provide a targeted, efficient solution to stabilise the road and prevent further degradation.

Alternative Methods Considered

Traditionally, highway repair methods would involve full-depth reconstruction or deep excavation, both of which are time-consuming, costly, and disruptive. Alternative approaches include:

• Full-depth reconstruction: Involves completely removing and replacing the road foundation, leading to prolonged road closures and significant material waste.
• Pavement structure placement: Would require breaking out sections of the rigid road and pouring new slabs, causing extended downtime and higher carbon emissions.
• Cementitious grouting: A potential solution, but it lacks the precision of geopolymer injection and can result in excessive material use with slower curing times.

Why Geobear?

Geobear’s geopolymer injection technology was selected due to its ability to:

• Target and fill voids with minimal disruption.
• Provide rapid curing, allowing traffic to resume quickly.
• Offer a non-invasive alternative to traditional excavation methods.
• Extend the lifespan of the existing rigid road structure without the need for full reconstruction.
• Offer a low-carbon method to deal with subgrade degradation

Geobear Solution

The project was divided into two phases, covering approximately 3km of the southbound carriageway. A high-quality Ground-Penetrating Radar (GPR) survey was subcontracted to identify areas of voiding and instability. Based on these findings, Geobear designed and delivered a bespoke treatment. throughout the affected areas. For the affected areas, Geobear drilled through the rigid road into the sub-base at varying levels depending on the depth of the issue. A geopolymer material was then injected as a liquid and expands to fill the voids and strengthen the underlying soils. The expansion fills voids, consolidates the soils and reinstates the contact between the underlying soils and the pavement structure. The works on this site entailed and achieved the following:

• Injections were done at 1m grid and reached depths up to 1.5m beneath the rigid road, tailored to the severity of voiding in each section. 
• Multiple levels of injection were used in some areas to address both surface and deeper instability.
• The total length of Geobear injection work for the scheme was 1,470 metres of dual carriageway.
• Traffic management was carefully coordinated with the local council to minimise disruption, allowing sections of phase two to be completed within the traffic management setup for phase one, significantly reducing project time.
• The road remained open during the day, with overnight closures implemented for efficiency.
• The injection purpose was carefully monitored using lasers with high precision to ensure the road surface was not affected. 
• Testing from pre and post injection revealed that the ground was improved up to 180%.

Carbon Savings

This scheme involved Geobear’s geopolymer injection solution to strengthen the road foundation of 150 concrete bays, offering a sustainable alternative to traditional concrete bay replacement. With knowledge of the carbon emissions of Geobear works, we can outline the carbon savings achieved by using Geobear’s method instead of conventional excavation and reconstruction.

Carbon Footprint Comparison

Total Carbon Reduction: 326.7 tonnes CO₂e (62.43% reduction)

What This Means for Sustainability

By choosing Geobear’s geopolymer injection, the A10 project avoided the release of over 326 tonnes of CO₂e, a 63% reduction in carbon emissions; equivalent to:

• Eliminating the emissions of 70 average UK cars for a year
• Saving the carbon footprint of 40 UK households annually
• Preventing the need for 5,400 tree seedlings growing for 10 years

Time Savings Compared to Traditional Replacement

Together with the carbon savings, Geobear’s method brings significant time savings to schemes of this nature. A full-depth replacement would result in a project duration of 5 to 10 months. By contrast, Geobear completed the entire project in under 6 weeks, making the solution at least 4 to 7 times faster than traditional methods. This drastically reduced disruption, allowing the road to remain operational during the day and significantly improving project efficiency.

For further information please contact Marcelo Silva [email protected]