The project required a cut and fill exercise to maximise the amount of developable area, and from an early stage in the project Phi Group assisted site developers Morbaine Limited with the design of the retaining structures to achieve this.

Consequently Phi's proposals were incorporated within the Main Contract Tender package. The successful Contractor, Britannia Construction, then instructed Phi Group, to undertake the design, supply and construction of three different retaining walls.

Firstly, the Client needed to widen the crest of an existing embankment in order to accommodate an adoptable footpath and cycleway. Phi Group proposed the use of their Soil Panel RS system at a 60º profile which utilises reinforced soil techniques for stability and encapsulates a 250mm thick layer of topsoil to provide a sustainable, low maintenance vegetative cover similar to the original embankment.

Consequently, they proposed the use of their Permacrib/Soil Nailed System. This system combines the top down soil nailing technique to support the excavated face thereby providing a secure temporary earthworks profile both in the short and long term. The soil nails were installed from the top downwards against a 70º cutting and the Permacrib from the bottom upwards at a face batter of 4V:1H with the soil nails extended to interlock with the Permacrib to form the long term permanent works. For retained heights up to 4.0m Phi Group proposed the use of their Permacrib System constructed at a 4V:1H batter and designed as a gravity retaining wall. Cost savings were made by using Permacrib as a gravity wall at the lower heights where soul nailing was unnecessary.

For the third structure the existing ground levels needed to be built up to the proposed finished road profile with fill material. Phi Group, therefore, proposed the use of their pre-cast concrete Titan Modular Block System incorporating soil reinforcement to form the reinforced soil mass. The maximum height of this wall was 2.5m and approximately 25metres long.

Speed of installation was also a factor as all Phi's solutions could be installed in only 15 weeks. Phi Group is expected to complete the walls in September, within budget and on programme. The Main Contract is expected to be finished during November allowing Tesco to undertake the fit out for the store which is to open before Christmas.