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Rail

Stabilising a high-speed level crossing

Challenge

A newly rebuilt concrete level crossing suffered 60 mm settlement within a year, causing geometry faults, poor ride quality, and ongoing maintenance from weak, peat-rich subgrades.

Solution

Geobear stabilised the crossing using geopolymer injection, lifting slabs to tolerance, restoring stiffness, and extending service life by 22 years — all completed within a single weekend.

95%

Reduction in CO₂ emissions versus full reconstruction

22 Years

22 years projected life extension before re-treatment

0.004 mm/day

Post-treatment settlement rate (down from 0.3 mm/day)

Background

Concrete level crossings are among the most maintenance-intensive railway assets. Their frequent exposure to dynamic axle loads, poor drainage, and weak subgrades often leads to progressive settlement, loss of geometry, and service-affecting ride quality issues. At the Swineshead Level Crossing in northeast England, settlement of up to 60 mm below design level was recorded less than a year after reconstruction. The cause was attributed to soft peaty soils and inadequate drainage, resulting in geometry deterioration at a rate of 0.3 mm/day.


The conventional remediation approach—complete reconstruction—involves excavation, heavy plant, extensive logistics, and long possessions. This disrupts railway operations, increases embodied carbon, and imposes high costs on asset owners.

Traditional approach and its limitations

A full level-crossing renewal typically uses new precast concrete slabs, ballast, sleepers, and rails. It is labour-intensive and demands long track possessions, usually bank-holiday blockades, with significant waste generation and fuel consumption. Carbon analysis shows that a full reconstruction emits nearly 200 tonnes CO₂e, with over 93% of emissions from raw material production. While this method restores full design geometry and offers a lifespan of 15–20 years, it is expensive, slow, and environmentally inefficient.

From rapid deterioration to long-term stability — Geobear restored performance and sustainability at 90 mph without excavation or disruption.

Geobear’s alternative: geopolymer injection

Geobear introduced a geopolymer injection system to stabilise the subgrade and lift the slabs back to tolerance without excavation. The technique involves drilling 12 mm holes through the slab and injecting expanding geopolymer resin into the Type 1 sub-base approximately 50 mm below the slab, with slab lift monitored by laser levels. The system achieves a lift within +0 / −10 mm, as per TRK/2102 specifications, restoring design geometry rapidly.

 

Design approach and implementation

The design focused on improving the stiffness of the sub-base and redistributing stresses through the soft subgrade. Injection points were arranged to ensure uniform coverage beneath the slab and transition zones. The geopolymer resin expands under controlled pressure, compacting voids and weak zones. Injections were executed during two weekend shifts, avoiding full possession.
Instrumentation included laser monitoring of lift, measurement train runs to track post-treatment performance, and differential geometry control to prevent twist faults.

Verification and post-treatment performance

Parameter

Before Treatment

After (May 2021)

After (July 2021)

Down line – track quality

17.6 mm

5.57 mm

5.98 mm

Up line – track quality

20.0 mm

4.3 mm

5.0 mm

Vertical geometry fault

33–35 mm

9–10 mm

9–10 mm



The rate of deterioration dropped from 0.3 mm/day to 0.004 mm/day, implying a 22-year life extension before reaching pre-treatment geometry levels.

ballast crossing before after diagram

 

Carbon and Productivity Benefits


A carbon life-cycle assessment compared Geobear’s system with full reconstruction:

 

 

Metric

Geopolymer Injection

Full Reconstruction

Total CO₂e (per intervention)

3.25 tonnes

199 tonnes

Reduction vs. conventional

−95.1%

—

Required interventions over 60 years

3

1

Net CO₂e over 60 years

9.7 tonnes

199 tonnes

 

Even with three interventions over six decades, geopolymer treatment cuts lifetime carbon emissions by 95%. Additionally, installation is 43% cheaper and completed in one weekend rather than during a long blockade.


Advantage of Geobear’s system

  • Rapid, non-invasive repair: Minimal excavation, no slab replacement.
  • Smart material control: Geopolymer expansion is self-modulating, ensuring uniform lift.
  • Sustainability leadership: Demonstrated carbon reduction aligns with UK Net Zero 2050 targets.
  • Operational continuity: Network remains open with only short possessions.
  • Data-driven verification: Continuous geometry monitoring confirms long-term effectiveness.


Conclusion

The Swineshead Level Crossing project confirms that geopolymer injections are a technically sound, sustainable, and economical alternative to full reconstruction. By stabilising the subgrade and restoring geometry quickly, Geobear’s solution has extended asset life by over two decades, reduced carbon footprint by 95%, and delivered measurable gains in network productivity. This innovation provides a model for low-carbon, high-efficiency railway maintenance adaptable across diverse rail infrastructures worldwide.

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