Emergency ground strengthening at the M11 Girton interchange

• Traffic impact: Closure of this section would have caused severe congestion on the M11, A14, and A428, affecting commuters and freight movements to Stansted and strategic ports.
• Technical demands: Works required a compressive strength of 4 MPa while maintaining surface movement within ±5 mm to protect adjacent bridge wingwalls.
• Investigative limits: Restricted traffic management precluded extensive ground investigation, requiring real-time adaptability during delivery.
• Programme pressure: Emergency intervention was needed quickly, with minimal impact on the ongoing A14 improvement scheme.

Geobear, working with Highways England, WSP, Interserve, and Kier Highways, designed and delivered an emergency geopolymer injection scheme:

• Injection process: Resin was injected beneath the carriageway to depths of up to 2.5 m, rapidly filling voids and reinstating soil contact.
• Controlled expansion: “Trigger time” methodology ensured resin expansion remained predictable and pavement heave stayed within ±5 mm.
• Real-time adjustments: Engineers adapted injection spacings and volumes to respond to unforeseen voiding conditions.
• QA and monitoring: CCTV verified void fill, laser levels monitored surface movement, and Falling Weight Deflectometer tests confirmed post-treatment performance.
• Accelerated delivery: Four crews worked in parallel across north and south abutments, enabling early completion.

The works were completed two days ahead of programme, within budget, and with no safety incidents. The carriageway was stabilised, risk of collapse eliminated, and the motorway reopened every morning, ensuring disruption was limited to overnight closures only.

Compared with excavation, the project avoided at least five weeks of disruption. This aligns with the Volterra Transport Study, which found that faster road maintenance on high-demand routes like the M11 can deliver £640–£7,400 of user savings per kilometre of works, with national annual savings of £70m–£87m if adopted more widely.

Carbon benefits were also clear: geopolymer injection generated ~45% lower CO₂ emissions than cementitious alternatives, as verified by independent analysis.

The project was recognised across the sector, covered by the BBC, and commended by the Chartered Institution of Highways & Transportation.

Testimonial

Karl Brooks, Project Sponsor, Highways England:

“Geobear’s solution to the essential embankment repair at M11 Girton interchange has been a highlight of this year’s programme. The geopolymer injection provided an innovative response to voiding, allowing us to effectively manage this complex stretch of motorway. Monitoring of pavement heave was impressive, and the programme of delivery outperformed comparative methods. Collaboration with WSP and Interserve meant we met — and in some cases exceeded — the requirements of the network and our stakeholders.”