Following a highway collapse in the village of Godstone, Surrey, Mainmark was appointed to deliver a ground improvement solution to address weak ground conditions associated with historic shallow sand mine workings and underground void migration. The incident, widely reported as a sinkhole event, highlighted the challenges posed by legacy underground voids beneath critical infrastructure.

Using Teretek® resin injection technology, Mainmark strengthened the ground beneath key sections of the highway network, helping support its safe reopening while minimising disruption to residents, businesses and road users.

Addressing Ground Instability following the Godstone Sinkhole

A significant highway collapse occurred in Godstone, Surrey, linked to historic shallow sand mine workings and the migration of underground voids beneath the village centre. The resulting instability affected two critical areas, High Street and Salisbury Road, requiring urgent intervention to restore ground confidence and support the reinstatement of the highway network.

While public attention focused on the visible sinkhole, the underlying challenge extended beyond the surface collapse itself. Ground conditions across the affected area required investigation and targeted strengthening to mitigate the effects of subsurface voiding and improve long-term asset performance.

Traditional excavation and replacement methods would have been highly disruptive, time-consuming and costly within a busy village environment. A solution was required that could strengthen the ground effectively while maintaining access and minimising impact on the local community.

Strengthening Weak Ground beneath Critical Highway Infrastructure

Mainmark deployed its specialist Teretek® geopolymer resin injection technology to improve the ground conditions beneath the affected highway areas. The solution involved injecting expanding resin through a carefully designed network of treatment locations to fill voids, permeate weak soils and improve load-bearing characteristics.

The treatment programme included:

• 586 resin injection locations.

• Treatment depths of up to 4 metres.

• Approximately 250m² of ground improvement.

Delivery across two treatment areas within a three-week programme.

Throughout the works, Mainmark utilised continuous laser level monitoring capable of detecting movement to ±0.5mm, alongside digitally recorded injection volumes, depths and flow rates to ensure precise control and quality assurance.

Pre- and post-treatment Dynamic Cone Penetrometer (DCP) testing was also undertaken to verify measurable improvements in ground strength and confirm the effectiveness of the solution.

Outcomes:

The project was successfully completed within a three-week programme, delivering targeted ground improvement with minimal impact to the surrounding area. Approximately 600 injection points were installed across the two treatment zones, addressing weak ground below ground level and supporting the reopening and long-term performance of the highway network.

The fully monitored process provided measurable validation of the ground improvement achieved and confidence in the consistency and long-term performance of the treated areas.

“We were able to deliver ground improvement across multiple load points within a short programme, while maintaining minimal impact on site operations. The fully monitored process provides confidence in both performance and consistency of results.”

David Hedley, Infrastructure Lead

Key Benefits of Teretek Resin Injection for Highways Remediation Works

Minimal Disruption

Teretek® resin injections enabled ground improvement works to be completed without extensive excavation, reducing disruption within the village environment.

Rapid Delivery

The project was completed within just three weeks, helping support the timely restoration of the affected highway infrastructure.

Verified Performance

Continuous monitoring and DCP testing provided measurable evidence of improved ground strength and load-bearing performance.

Lower Carbon Solution

Compared with traditional dig-and-replace methods, the solution delivered lower embodied carbon and generated minimal waste throughout the works.

Long-Term Asset Resilience

The treatment strengthened weak ground conditions associated with historic voiding, helping improve the long-term performance and resilience of the highway asset.