Bespoke Void Remediation Solution for Footpath at Dawlish

Protecting Critical Rail Infrastructure from Coastal Erosion

Coastal environments present unique challenges for infrastructure owners. At Dawlish, Devon, ongoing coastal erosion and rising tidal activity caused severe subterranean washout beneath a public footpath located directly adjacent to operational railway infrastructure. Immediate intervention was required to prevent further ground loss, re-support the affected area and protect nearby rail assets

The Challenge

Coastal erosion and rising tides caused severe subterranean washout beneath a public footway directly adjacent to Network Rail lines in Dawlish, Teignbridge.

Restricted site access hindered standard material transport and conventional equipment setup.

Urgent intervention void fill was needed to reinforce the footpath and prevent potential collapse or damage to surrounding rail assets.

The Solution

To overcome the site's challenging access restrictions, Mainmark developed a bespoke material delivery and injection system specifically designed for this location. This innovative approach allowed specialist materials to be delivered precisely into the treatment zone without the need for large-scale equipment or disruptive construction activity.

• The team utilised high-expansion Geofoam technology to:

• Fill and eliminate the subterranean void.

• Displace trapped water within the affected area.

• Compact adjacent soils.

• Restore load-bearing support beneath the footpath.

• Protect adjacent rail infrastructure from future ground loss.

The lightweight nature of the Geofoam material ensured that additional loads were not introduced into already weakened ground conditions while still delivering the required structural performance.

Monitoring & Validation

• Continuously monitored foam expansion and structural movement to ensure precise void filling without dynamic heave.

• Verified target density and material performance through rigorous Quality Assurance testing and daily MQT field cup logging.

Outcomes:

The project was completed within a four-day programme and successfully addressed the underlying causes of the footpath instability. The void was fully remediated without impacting railway operations, passenger services or public safety.

Project outcomes included:

• Successful void remediation beneath the footpath.

• Restoration of load-bearing capacity.

• Protection of adjacent rail infrastructure.

• Prevention of continued tidal washout and soil migration

• Zero operational delays to railway services.

• Delivery within a rapid four-day programme