2019
Gatwick, Sussex
Highways England
Kier Group
CAN Geotechnical Ltd
M23 Smart Motorway Upgrade (Junction 8–10) Sustainable Retaining Wall Solution Using Green Terramesh
Completed Structure
Site before construction
Green Terramesh® and soil nails during construction
Green Terramesh® and soil nails during construction
Vegetation established in Green Terramesh®
Challenge
The M23 motorway is a critical element of the UK strategic road network, linking Crawley, Gatwick Airport, and Brighton to the M25, which provides access to London and the wider UK. As part of the Highways England M23 Junction 8 to 10 Smart Motorway upgrade, approximately 10 miles of motorway were enhanced to increase capacity and improve traffic flow. This was achieved by converting the hard shoulder into a permanent running lane, creating four lanes in each direction.
A key engineering challenge within the scheme involved widening the northbound segregated left-turn lane to accommodate an additional traffic lane. The project faced significant spatial constraints, as the widening needed to be delivered within a tight corridor without expanding the existing project footprint. Limited land availability ruled out conventional retaining wall solutions, requiring a more space-efficient and innovative approach.
Solution
To overcome the restricted site conditions, engineers implemented a hybrid reinforced soil and soil nailing solution using Maccaferri’s BBA HAPAS-approved Green Terramesh system, designed for a 120-year service life. This approach combined the benefits of reinforced earth structures with hollow bar soil nails installed through the front face, enabling a structurally efficient solution within minimal space.
The Green Terramesh system features an integrated steel mesh geogrid tail, which is embedded into compacted structural backfill to provide effective soil reinforcement. The units also include a durable welded mesh front panel and internal bracing struts, ensuring stability and correct alignment during installation. This eliminates the need for temporary formwork or external supports, significantly reducing construction time and improving on-site safety.
As a modular, factory-assembled system, Green Terramesh reduces labour requirements and accelerates installation compared to traditional reinforced earth or wrapped-face solutions. Seeded topsoil is placed directly behind the face, enabling rapid vegetation growth and creating a green retaining wall.
Once established, the vegetated face delivers a natural, aesthetically pleasing finish that integrates seamlessly with the surrounding environment. The solution not only meets structural and spatial requirements but also enhances sustainability by supporting biodiversity, creating habitats for wildlife, and improving air quality through carbon dioxide absorption.
Keywords: M23 smart motorway, retaining wall solution UK, reinforced soil wall, Green Terramesh, soil nailing, sustainable infrastructure, highway widening, geogrid system, Maccaferri UK, smart motorway construction
Used Products
