Reinforced Soil Retaining Wall in Luton Sustainable Chalk Stabilisation with Mineral Terramesh®

A former Vauxhall Motors factory site on the outskirts of Luton was acquired by Redrow Homes for residential development, offering a prime location but presenting significant engineering challenges. The brownfield site featured steeply sloping terrain composed of structureless chalk, a material with limited load-bearing capacity and poor stability when left untreated.

To maximise land use efficiency and enable viable housing layouts, the development required the formation of a series of engineered terraces. One key area demanded the construction of a retaining structure approaching 10 metres in height. The combination of steep gradients, weak chalk geology, and the scale of the proposed earthworks created a complex geotechnical problem requiring an innovative and cost-effective solution.

Rather than disposing of excavated chalk and importing quarried fill material, contractor GDL, designers GES, and Maccaferri developed a sustainable value-engineered solution. By applying cement stabilisation, the site-won chalk was repurposed as structural backfill for a reinforced soil retaining wall. This approach significantly reduced waste, eliminated off-site disposal, and minimised the environmental impact associated with importing new materials.

Maccaferri designed and supplied a Mineral Terramesh® reinforced soil retaining wall system, enabling the construction of a 9.6-metre-high structure with a steep 70° face angle. The system was reinforced with ParaGrid® polymer geogrids, providing long-term stability and ensuring performance under load in challenging ground conditions.

The Mineral Terramesh® system is manufactured from double-twist woven wire mesh, made from Zn-Al 5% galvanised steel and enhanced with a PoliMac® polymer coating. This advanced coating technology delivers a design life exceeding 120 years and is fully BBA HAPAS approved, offering superior durability and environmental performance compared to traditional PVC-coated alternatives.

From a construction perspective, the solution improved efficiency through factory-assembled facing units, combining woven mesh with a Class A galvanised welded mesh (50mm x 50mm apertures). This not only provided an architecturally appealing finish but also accelerated installation by reducing on-site assembly requirements. The system allows the use of smaller facing aggregates (typically 75mm clean stone), enhancing both buildability and visual consistency.

Each Mineral Terramesh® unit includes integral 3-metre reinforcement tails, forming a continuous connection between the facing and the reinforced soil mass. This ensures structural integrity while maintaining flexibility and adaptability during construction.