A LARGE reinforced earth retaining structure in Nottinghamshire is the UK's first combined use of Green Terramesh and Terram ParaDrain according to supplier Maccaferri.
The structure is part of a housing development at Berry Hill Park which overlooks the town of Mansfield and was once a vantage point for royal hunting parties in Sherwood Forest. More recently it has been the site of extensive quarrying.
Several housebuilders are involved in the scheme, which includes open spaces, footpaths, a cycle way and community facilities.
Kings Stand, on the southern perimeter, is being developed by McLean Homes Northern. The site is on the upper rim of the disused quarry and a retaining structure was needed to stabilise the area next to the development's spine road.
Designer Eastwood & Partners specified that the retaining system had to be environmentally friendly and in harmony with the countryside.
Geosynthetic manufacturer and supplier Maccaferri's solution for the 300m long and 8.5m high retaining wall uses reinforced soil incorporating a Green Terramesh retaining wall with a Terram ParaDrain geogrid manufactured by Linear Composites.
Main contractor was Newark Development, with sister firm Loates Construction carrying out earthworks and construction of the retaining structure.
The Green Terramesh units are formed from a single sheet of hexagonal double twist woven steel mesh. When installed they are formed into three sections, a horizontal soil reinforcement layer, a facing section and a horizontal return top layer. An inbuilt layer of biodegradable coir geotextile in the front face is used to retain the topsoil until the vegetation becomes established.
Maccaferri says that by using the retaining system with the ParaDrain, excess pore water is dissipated, increasing the structure's stability.
ParaDrain consists of two elements: a polyethylene coated polyester cored reinforcement strip and a built-in drainage channel with a bonded nonwoven fabric layer. The fabric layer acts as a filter allowing water to drain away from deep within the reinforced soil block while retaining the backfill material.
To help the wall blend in with its surroundings, topsoil was placed behind the face of the Terramesh and the slope seeded with local plant species. Planting terraces help create a natural effect and prevent the final slope from looking too 'engineered'