Jempsons Superstore, Soil Nailing

Jempson's the independent family run Grocers wanted to extend their business on their existing site in Peasmarsh, East Sussex. A decade earlier soil nails had been used in the site construction for the original store and soil nails were again the solution to stabilise the large excavated faces formed when extending further into the sloping site.

The intention was to build a new store on the newly created area and use the area of the existing store for parking. The woodland setting of the store meant a 'green face' natural setting was desirable for the high retaining walls.

Ground conditions were Tunbridge Wells sand overlaying Wadhurst Clay, with a perched water table at the junction of these materials. Adit water drains wrapped perforated pipes were installed through the clay and into the base of the water bearing sand layer as the excavation reached this level to control water flows.

Phi Group design solution involved using their Soil Panel system attached to Soil Nails used to stabilise the earth block. Top down construction was used with Phi Group nailing the excavated faces and stabilising the exposed face with the rear structural panel of their Soil Panel System in each excavated layer before the groundworker commence excavation of the next layer.

Phi Group installed Dywidag Gewi-steel solid soil nails into pre drilled holes and grouted using a tremie pipe to form the stable gravity soil block. Phi Group carried out pull out tests on trial soil nails in both the sand and clay layers to confirm their design assumptions before commencing work.

On completion of the excavation, soil nailing and fixing of structural facing mesh, the facing panels of the Soil Panel system were added and filled with soil growing medium and seeded to achieve the natural grassy bank finish to this engineered structure.