Rail

Emergency railway ground stabilisation and void remediation in Grange-over-Sands

Challenge

A developing sinkhole beneath a live coastal railway threatened track stability, demanding immediate ground remediation with minimal operational disruption.

Solution

Geobear rapidly stabilised subsurface conditions using engineered geopolymer injection techniques, restoring ground integrity without excavation or prolonged possession requirements.

1 day

Emergency resposne

Approx 10m3

Void remediated

100 kPa

Material strength

Background

Following the emergence of a sinkhole beneath a coastal railway embankment near Grange-over-Sands, immediate intervention was required to safeguard the operational railway. The void had developed beneath the existing track formation, creating the potential for progressive ground loss and compromising the support provided to the railway infrastructure.

Given the critical nature of the asset, the remediation strategy needed to deliver rapid structural stabilisation while avoiding extensive excavation, reducing possession requirements and limiting disruption to railway operations.

Challenge

The project involved emergency treatment of a significant subterranean void beneath an operational railway where conventional excavation and replacement techniques would have introduced considerable programme, safety and logistical challenges.

The principal engineering challenges included:

  • Emergency response to an active sinkhole beneath live railway infrastructure.
  • Restoring load transfer within weakened ground without introducing additional loading.
  • Delivering the solution within a restricted railway possession and constrained coastal access environment.
  • Pumping material into an inaccessible underground cavity whilst maintaining precise control over expansion and fill.
  • Achieving rapid strength gain to allow the railway asset to be safely returned to service.

The remediation required a solution capable of penetrating inaccessible voids while providing controlled expansion and immediate structural benefit without disturbing the surrounding formation.

Solution

Geobear designed and implemented an emergency geopolymer void remediation solution specifically developed for railway infrastructure applications.

Following site establishment by the principal contractor, specialist injection tubes were inserted directly into the void before a two-component expanding geopolymer was pumped through a self-contained injection system. The material mixed at the point of injection, rapidly expanding to occupy the entire cavity whilst exerting minimal additional dead load on the surrounding ground. The material cured in situ, forming a lightweight structural fill capable of restoring support beneath the railway.

The selected engineering material provided:

  • Lightweight void replacement to minimise additional loading.
  • Controlled expansion to achieve complete cavity filling.
  • Rapid curing characteristics suitable for emergency rail possessions.
  • Compressive strength of approximately 100 kPa when tested in accordance with BS EN 826.
  • Minimum density of approximately 36 kg/m³, providing structural support without significantly increasing ground stresses.

The installation utilised Geobear's mobile injection equipment, enabling material to be pumped remotely from a self-contained unit, allowing the treatment to be completed despite restricted site access. The entire emergency remediation was completed during a single working shift.

grange-tubes

 

Results

The emergency works successfully restored the integrity of the railway formation by completely remediating the underground void before further deterioration could occur.

Key project outcomes included:

  • Emergency stabilisation completed within a single shift.
  • Approximately 10m³ of underground void remediated.
  • No large-scale excavation or reconstruction required.
  • Minimal disruption to railway operations and surrounding infrastructure.
  • Lightweight engineered fill restored ground continuity while reducing long-term settlement risk.
  • Safe, controlled installation delivered within a highly constrained rail environment.

The project demonstrates how engineered geopolymer technologies can provide rapid, technically robust solutions for emergency railway ground failures, significantly reducing programme duration and operational disruption compared with traditional excavation-based remediation techniques.

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