Tensar offers ground stabilisation with geogrid

Tensar geogrid technology has been used for extensive ground stabilisation at Kier's development of a major new supermarket in Newport, Gwent.

Located on the former Crindau coke-fuelled gasworks close to the banks of the River Usk, the store project is on track for completion before the 2010 Ryder Cup.

There were a number of potential differential settlement problems on the site due to the extremely variable bearing capability of the ground with extensive transition zones.

Tensar geogrid saved up to 6 or 8 weeks piling time on site, as well as substantial costs.

The versatility of being able to install Triax where extra ground stabilisation is required is of great benefit.

The underlying ground included the alluvial river soil deposits, the shelf of rock at the western corner which slopes sharply down towards the east along the access side and the extensive made ground on the old industrial site.

Apart from cost, the major constraint was to have the store open to service the influx of golf spectators anticipated for September's 2010 Ryder Cup at Celtic Manor five miles away.

One option would have been to pile the whole site; apart from the high cost, this would have taken too long.

Instead, Tensar's Technical team developed a geogrid-based design solution for the access road and bridge abutments; this meant that only piling under the 7000m2 store itself, the petrol station and one of the abutments was required.

The main A4042 road providing access to the store is 9m above the car park design level, and is connected by a 25m long road bridge.

To create the 6m high abutments at the western end of the bridge, where rock runs under the construction, Tensar proposed a BBA certificated Tensartech wall system featuring uniaxial geogrids and faced with the attractive modular blocks.

At the eastern end of the abutments, to mitigate differential settlement and improve load bearing performance over the transition to alluvial soils, layers of Tensar Triax were used to create a transition zone to a concrete slab over piles, installed beneath capping between the Tensartech abutment and ramped walls.

The fill behind the abutments utilised Class 6I graded granular fill.

Maxit Light Weight Aggregate was installed for the ramped access road at the eastern end to ensure a low weight overburden on the poor strength underlying formation.

The Tensartech wall system features dry laid facing blocks which are firmly connected with Tensar's polymer key to layers of uniaxial geogrids placed within the fill.

Tensartech is rapid to build, as it requires no formwork or crane lifts, and a fully-load bearing structure can be installed without waiting for concrete to achieve design strength.

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