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Sewer pipe belly lifting on new build development

Overview

Client: UK New Build Contractor

Location: North West

Project Focus: Ground strengthening and pipe lifting for failing shallow sewers beneath a road network on a new-build housing estate.

Road closure not feasible

The Challenge: Structural Integrity in Soft Ground

A sewer system constructed beneath a road on a new housing development was compromised by weakness in the soft alluvium soil. Post-installation CCTV surveys had revealed that a number of the sewer pipes had bellies in them. Pipe bellies occur when the ground beneath weakens and does not have the strength to keep the pipe in place, this results in a belly which is illustrated by standing water in the pipes.

This issue affected five different locations across the development. The areas required geopolymer treatment work to minimise the bellying for the assets to be adopted by the local utility company.

There were several challenges to address on the site

  • Complex Ground Conditions: The sewers were located atop 7-10 metres of very soft alluvium, offering limited natural support.
  • Active Road Network: Any remedial works would need to avoid major disruption to the estate’s operational road system.
  • Long-Term Viability: A solution was needed that not only resolved the immediate issues but also provided durable, future-proof results.

Alternative methods and limitations

The traditional approach to this challenge would require an excavation of the site, which given the live status of the development was not viable. An excavation would be invasive, time-consuming, and environmentally damaging. In addition, the extensive excavation and backfill activities would disrupt the entire road network and there is risk of collateral damage to nearby utilities and infrastructure.

 

Geobear Solution

One of five locations

Geobear’s geopolymer injection technology offered a bespoke solution, perfectly tailored to the project’s unique challenges. A solution was designed that would see the injection of geopolymer material into the areas beneath the failing pipes. The material is injected as a liquid and reacts in the ground, expanding to fill voids and reinstate ground strength, the expansion would also lift the pipes and minimise the scale of the bellies.

On this site, the process included:

Precision Ground Improvement:

  • Multi-depth geopolymer injections between 0.1m and 3.1m below the sewer pipe invert.
  • Injection points spaced 1.0m apart along the sewer length.

Minimal Disruption:

  • All work was completed using injection holes, avoiding the need for road closures.
  • Equipment was compact and self-contained, ensuring the estate’s road network remained fully operational.

Performance Assurance:

Real-time monitoring allowed for the precise lifting of the sewers where the standing water reduction illustrated lift and reduced bellying.

The watermark shows where standing water was post-lift

 

Key benefits

Geobear’s system was an ideal solution for the challenge bringing several key benefits:

Environmental Sustainability:

  • Compared to alternative methods, the geopolymer solution emits significantly less carbon emissions (Based on Carbon Footprint report data).
  • Lightweight equipment and reduced material usage contributed to a significantly lower environmental impact.

Speed and Cost Efficiency:

  • Rapid deployment and minimal disruption meant the project was completed within 8 days.
  • Avoided the high costs associated with road closures and prolonged project timelines.
  • Neighbourhood residents were minimally affected by the works and could continue their daily lives as normal.

Preservation of Infrastructure:

  • Enhanced the structural integrity of the sewers, ensuring long-term durability without the need for invasive reconstruction.
  • Enabled the adoption of the sewers by the local utility company.
  • Protected the operational road network, preserving community access and convenience.

 

Modern Asset Preservation

For engineers focused on preserving critical infrastructure, Geobear’s geopolymer injection technology represents a game-changing solution. This project demonstrated its ability to address complex subsurface challenges with minimal disruption, exceptional environmental performance, and long-lasting results.

As emergency works become increasingly common in aging and new-build infrastructure, Geobear offers a sustainable, cost-effective approach that ensures infrastructure remains operational while protecting communities and the environment.

 

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