Sandbag formwork favoured over traditional
shutter system for the construction of a curved
road embankment.

Background
Galliford Try Construction completed Phase 2 of a project on behalf of Warwickshire County Council at the former Midland Quarry Site near Camp Hill, Nuneaton, in June 2005.
The works involved the construction of a roundabout and 300m of new access road, 100m of which is supported by a reinforced soil embankment. The road forms the new entrance to the 100 year old quarry site which is being developed for new housing and light industry. The road also provides a bypass route for HGV’s which previously passed through a residential area.
Site challenges
The geometry of the access road comprises a number of sweeping curves, the majority of which are on embankments. Soil reinforcement was incorporated into a section of the side slopes approaching the roundabout.
These steepened side slopes prevent the embankment from encroaching into an environmentally sensitive wetland area adjacent to the toe of the slope.
The face angle of these slopes increases from 30 to 60° as the access road climbs up to the roundabout. This variable face, combined with the sweeping curves, presented a construction challenge for Galliford Try as conventional reinforced soil shuttering systems would not be best suited to the variable geometry required.
Solution
Galliford Try contacted HUESKER Ltd, manufacturer of geosynthetic reinforcement products, for advice on the design and construction of the reinforced soil slopes. A SEAF, (Strengthened Earthworks Appraisal Form), was submitted based on Huesker’s design, and was subsequently approved by Warwickshire County Council.
The approved design used horizontal layers of HUESKER’s BBA-certified Fortrac® geogrid installed in 600mm lifts for slope angles between 30 and 45°. For steeper face angles, up to 60°, a wraparound face was detailed.

The fill material used as backfill for the slopes, which ranged in height from 3.0 to 4.5m, was a locally available stoney cohesive material.
With regard to the construction technique, HUESKER suggested an unconventional method which was the use of sandbags to form the front face of the wraparound sections.
These sandbags enabled the variable face angles and radii to be adhered to along the embankment face. The Fortrac® geogrid was wrapped around the face of the sandbags every fourth row. The sandbags at the face were filled with topsoil to provide a growing medium for hydro-seeding upon completion of the slopes.
This type of construction is used extensively in other parts of the world, however, in the UK it is more commonplace to use a rigid temporary face shutter or a sacrificial metallic mesh former, set at the prescribed face angle. Unlike conventional external shutter systems, the sandbag method does not have the added benefit of allowing the attachment of an edge protection barrier. Galliford Try overcame this by constructing a scaffold ‘fall arrest’ system behind the front face to protect site operatives from falling over the exposed slope edge.