Soil Reinforced Acoustic Bund for M4 Residential Development

The project involved a residential development site located adjacent to the M4 motorway, where two major constraints significantly influenced the design approach. Firstly, the high value of residential land meant that the available space needed to be used as efficiently as possible, leaving little room for wide or gently sloping earthworks. Secondly, the proximity of the motorway created substantial noise pollution, requiring an effective acoustic mitigation measure to ensure acceptable living conditions for future residents.

In response to these challenges, the client set out several key objectives. They required the construction of an acoustic barrier capable of reducing noise from the motorway to acceptable levels. At the same time, the solution needed to maximise land take by incorporating a steep-sided embankment, while still ensuring long-term structural stability. Additionally, the finished structure needed to blend into the surrounding environment, with a natural, vegetated appearance that would enhance the visual quality of the development rather than detract from it.

To meet these requirements, Maccaferri designed and implemented a soil-reinforced bund featuring a steep-sided embankment. The front face of the embankment was constructed at an angle of 60 degrees from the horizontal, allowing the structure to occupy minimal space while still achieving the required height and performance. The rear face was formed at a shallower 30-degree slope to ensure overall stability and integration with the surrounding ground profile.

The construction of the steep front face was achieved using a temporary rising shutter system. This method enabled the ParaGrid geogrid reinforcement to be wrapped around the face, creating an anchored and stable slope structure. To support vegetation and prevent soil loss during the early stages, a biodegradable erosion control matting, BioMac C, was installed. This matting retained the topsoil behind the slope face and provided short-term erosion protection, promoting rapid establishment of vegetation and contributing to the long-term aesthetic goals of the project.

Primary reinforcement of the embankment was provided by ParaGrid, ensuring the structural integrity of the soil mass over time. The completed bund reached a height of 6 metres and extended לאורך 1.2 kilometres, successfully delivering an effective acoustic barrier while optimising land use and achieving a natural, visually appealing finish.