Soil nailing was the cheapest solution for retaining this steep slope on the site of a new Tesco store in Ballymena, Northern Ireland.

Sheet piles would have been too noisy for nearby residents, and would have been difficult to install due to the number of boulders in the soil. A bored pile retaining wall would have cost more than twice as much.

Keller Ground Engineering installed more than 1,200 soil nails over a face area of 2,900m2 on the £0.5m contract. Part of the wall slopes at 55 degrees and here the soil is held in by a 100mm thick geoweb which allows vegetation to grow.

Where additional space was required closer to the new store, the slope steepened to 72 degrees and was sprayed with a 200mm thick reinforced concrete.

Keller used three rigs to install the nails, excavating from ground level one layer at a time down to about 12m. The hollow, threaded steel bars are driven in at 20 degrees below the horizontal to a length of 12m, after which grout is pumped through them to form a bond with the soil. The main contractor was Patton Construction and the consulting engineer was White Young Green.

Source

Construction Manager