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Utilities

Sewer pipe belly lifting on new build development

Challenge

Several newly installed sewers developed pipe bellies due to weak alluvial soils, preventing utility adoption — traditional excavation repairs would have caused major disruption to occupied estate roads.

Solution

Geobear injected expanding geopolymers beneath five sewer sections, compacting soils, lifting pipes back into alignment, and restoring gradients — completed in 8 days with zero road closures.

2 mm

Precision lift achieved

Zero interruption

To the network flow

10×

Faster than relining

Background

On a new housing development in the North West, post-installation CCTV surveys revealed that several sewer lines beneath estate roads had developed pipe bellies. These defects, identified by standing water within the sewers, were the result of settlement in weak underlying soils.

The sewers were founded above 7–10 m of very soft alluvium, offering little natural support. Over time, ground weakness caused sections of pipe to sag, creating hydraulic inefficiencies and blocking adoption of the assets by the local utility provider.
Five separate locations across the estate required urgent remediation to reinstate the long-term stability of the sewers while keeping the roads fully operational.

Challenge

The engineering challenges were clear:

  • Weak alluvial soils: The sewers were founded above deep deposits of soft silts and sands, which had insufficient bearing strength to hold pipe gradients over time.
  • Operational estate roads: Excavation and reconstruction would have required full road closures, displacing residents and risking collateral damage to adjacent utilities.
  • Asset adoption: The client needed a solution that not only corrected current defects but delivered long-term structural assurance acceptable to the adopting utility.

Traditional excavation was dismissed as too invasive, slow, and costly. An alternative was required that could be installed from the surface, restore gradients, and avoid disruption to the community.

Pipes lifted, roads open, problem solved — Geobear restored sewer alignment and utility adoption without a single excavation.

Solutions

Geobear designed and implemented a precision geopolymer injection scheme across the five defect locations.

  • Injection methodology:
    • Tubes installed at 1 m spacing along each sewer length.

    • Multi-depth injections delivered between 0.1 m and 3.1 m below invert level to compact soils, fill voids, and reinstate support.

  • Pipe lifting:
    • Controlled injection expanded beneath the pipes, lifting sagged sections.

    • Standing water within the sewers was reduced in real time, providing visual confirmation of lift and alignment.

  • Monitoring:
    • Continuous monitoring ensured pipes were lifted within tolerance and that adjacent infrastructure was unaffected.

  • Non-invasive delivery:
    • Compact equipment meant all works were completed from the surface, with no excavation or closures of estate roads.

This approach enabled effective correction of the pipe bellies while minimising disruption for residents.

Geobear process leaves minimal evidence in road way other than small holes that are subsequently grouted.

Minimal intrusion, small holes

Results

  • Five sewer locations treated, reinstating design gradient and flow.

  • Pipe bellies lifted and standing water eliminated in CCTV inspections.

  • No disruption to residents — estate roads remained open throughout.

  • Programme completed in 8 days, compared to weeks for excavation.

  • Carbon savings achieved by avoiding excavation, spoil removal, and reinstatement.
  • Utility adoption enabled, with long-term assurance of sewer performance.

This image is taken from the monitoring unit and illustrates the pipe belly where residual water is no longer present.

Pipe Belly after treatment

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Get in touch with our expert team today and discover how Geobear can extend the life of your critical infrastructure assets.

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