Housing development under extreme conditions

Situation

At Tuttle Hill in Nuneaton, a town in the British East Midlands, the housing developer Redrow Homes has developed an open quarry for conversion into residential land. Quartzite and diorite were quarried in the 1.5-hectare site until the late 1990s. It consists of a large ‘pit’ and a smaller, partially backfilled ‘shallow depression’.
The design of the reinforced embankment, which is to be constructed as geosynthetic-reinforced earth (GRE), must meet a wide range of temporary and permanent requirements.

Solution

By selecting a geogrid with low elongation, horizontal movements are reduced to a minimum and the relative density of the entire fill material is kept constant. The reinforced slope is constructed from layers of high-tensile polyester geogrids. Various geogrids with a maximum tensile strength ranging from 55 kN/m to 400 kN/m were used. The anchorage lengths vary between 8 m and 35 m. At the front of the slope, the geogrid is raised, folded over and back-anchored. To protect against wave erosion, the lower two-thirds of the embankment at Midland Quarry were reinforced with gabions placed in front. In the upper third, a layer of topsoil was installed to encourage vegetation growth above the waterline. The front face was constructed using climbing formwork.

Advantages

• Highly flexible solution during the design and construction phases
• Minimal and reliably predictable settlement
• Enables maximum development potential for residential construction
• Extremely cost-effective solution
• Sustainability through the use of building materials sourced on site