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Highways

A323 Clay Shrinkage Ground Improvement

Challenge

Shrinkable clay beneath the A323 caused progressive settlement and cracking, worsened by tree roots. Traditional excavation repairs would have been disruptive, carbon-intensive, and costly for Surrey County Council.

Solution

Geobear stabilised deep clay soils using geopolymer injection — the UK’s first of its kind — eliminating excavation, maintaining access, and reducing carbon emissions by 62%.

62%

Lower CO₂ emissions vs. traditional reconstruction

3.5m

Clay stabilised to depths of 3.5 metres

Zero daytime closure

No full road day closure — traffic and community access maintained

Background

The Aldershot Road section of the A323 in Guildford had suffered from progressive settlement and cracking due to the shrink–swell behaviour of underlying clay soils. Tree roots exacerbated the problem by withdrawing moisture from the clay, leading to ground movement and dips across the carriageway.

Traditional reconstruction would have required deep excavation, prolonged road closures, and major community disruption. Surrey County Council sought an innovative solution that could stabilise the clay subgrade in situ and extend the life of the asset while minimising impact on road users and residents.

Challenge

The project faced multiple constraints:

  • The underlying problem was deep-seated shrinkable clay, requiring treatment well below pavement level.
  • Traditional excavation would have disrupted a busy A road and impacted local businesses and residents.
  • Stakeholder management was critical, with a school and public house requiring continuous access during works.
  • Accurate treatment was needed to stabilise soils without damaging nearby utilities.

Client insight

We approached Geobear because it ticked many boxes for us: its solution is swift, economical, low carbon, enhances workplace safety and preserves access to surrounding utilities.

Surrey County Council

Solutions

Geobear developed and delivered a pioneering solution — the first use of geopolymer injection in the UK to stabilise shrinkable clay beneath a highway.

  • Resin was injected directly into the clay soils at depths of up to 3.5 m, increasing stiffness and reducing shrink–swell potential.
  • Each injection set within 15–20 seconds, reaching 95% strength in under 15 minutes, allowing resurfacing to proceed almost immediately.
  • Traffic management was designed to keep the road open, with daily communication ensuring access for the local school and pub.
  • Ringway Eurovia undertook resurfacing once the subgrade had been stabilised, reinstating a smooth and durable carriageway.
Safety on A323

Results

The project successfully stabilised the clay subgrade in situ, eliminating the need for excavation and safeguarding nearby services. Settlement was arrested, dips in the carriageway corrected, and the asset’s life extended.

Environmental benefits were significant: carbon emissions were reduced by 62% compared with traditional reconstruction, with further reductions from avoiding excavation spoil, vehicle movements, and trench support.

The A323 scheme marked a UK first in highway ground engineering and demonstrated how geopolymer technology can deliver long-term value while protecting communities and the environment. The approach is now being considered for wider adoption across other local authority road networks.

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Get in touch with our expert team today and discover how Geobear can extend the life of your critical infrastructure assets.

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