Innovative Load-Compensation Solution Protects High-Pressure Gas Main at Welborne Garden Village
Foamed Glass (UK) Ltd, part of the Thomas Armstrong Group, has successfully delivered an innovative geotechnical solution to overcome critical infrastructure constraints at the new-build housing development at Welborne Garden Village.
The master-planned new settlement, designed around traditional Garden City principles to create a long-term, sustainable community, required localised ground build-up to manage surface water and flood risk. However, an existing 1050NB / 1067 mm (42-inch) high-pressure steel gas main crossing the site imposed strict constraints on allowable loading and construction methodology.
The Technical Challenge
To meet design specifications, the required finished cover over the gas main needed to be increased to approximately 2.3–2.4 metres. Utilising conventional granular or cohesive fill would have resulted in unacceptable increases in vertical overburden stress, potentially breaching strict GM/1 and IGEM/TD/1 utility requirements.
The Engineered Solution
Civil designers Paul Basham Associates and structural/geotechnical consultants Saith Ltd specified a lightweight load-compensation strategy. The engineering team reduced the existing cover locally, removing 300 mm of heavy native soil and substituting it with an engineered layer of Foamed Glass FG40 ultra-lightweight aggregate.
This layer was locally combined with a Cellweb® Cellular Confinement system to distribute loads effectively over a wider area.
Typical Cross-Section Profile
- 75 mm – Class SA Topsoil & Seed
- 850 mm – Foamed Glass FG40 ultra-lightweight aggregate + Cellweb® Confinement
- 1.55 m – Remaining Native Cover
- 1067 mm High-Pressure Steel Gas Main (49.6 barg)
By substituting the dense native ground with the highly porous, 100% recycled foamed glass lightweight aggregate, the final configuration safely delivered a final cover to the pipe of 2.325 metres while achieving a reduction in overburden pressure. This successfully controls stresses during both immediate construction and long-term pipeline operations.
Logistical and Environmental Advantages
In addition to solving the structural loading challenge, the physical properties of Foamed Glass FG40 ultra-lightweight aggregate delivered major supply chain efficiencies on-site.
Because the material's bulk density is so low, material delivery is governed by volume rather than weight. Contractor Blanchard Wells Ltd and logistics partner Day Aggregates utilised walking-floor vehicles.
In practical terms, this allowed them to transport four to five times more material per load compared with conventional weight-limited tipper vehicles. This drastically cut vehicle movements to the site, lowering haulage costs, reducing programme impact, and significantly decreasing transport-related carbon emissions.
Project Directory
Project Location: Welborne Garden Village, Fareham, Hampshire
Build Type: New Build Housing
Foamed Glass LWA Supplier: Foamed Glass UK (Thomas Armstrong Group)
Civil Designer: Paul Basham Associates
Structural/Geotechnical Consultant: Saith Ltd
Contractor: Blanchard Wells Ltd
Geosynthetics Supplier: Geosynthetics Limited
Distribution & Logistics: Day Aggregates
For material enquiries, technical data sheets, or to discuss structural load-reduction specifications for your next project, contact the Foamed Glass UK technical team at technical.enquiries@foamed-glass.uk.