4 Warehouses at Wyvern Retail Park, Derby Triangle

Winvic approached Menard to find a cost-effective foundation solution for the development of four warehouses at Wyvern retail Park in Derby: Units A1 (4,633 m²), A2 (3,394 m²), C1 (6,821 m²) and D134 (11,457 m²). These four buildings developed by St Modwen are located on the Derby Triangle site which had been used in its past as a landfill. The slab of the unitshad to be designed to a FM2 specification to support a uniformly distributed load of 50 kPa, whilst the structure brought point loads of up to 1,800 kN SLS.

The site investigation revealed relatively heterogeneous ground conditions on each plot, with around 2.5 m to 8 m of made ground, with significant pockets of very soft cohesive material and large obstructions, underlain by natural medium dense sands and gravels and stiff clay. The presence of very soft cohesive pockets and obstructions was precluding the use of the specified Vibro Stone Columns without full remediation of the made ground prior the ground improvement works.

Menard offered to Winvic a solution of Dynamic Replacement (DR) in alternative to the base solutions consisting of the remediation of the made ground with clearance of the obstructions and soft pockets ahead of the use of Vibro Stone Columns. The use of DR allowed the ground improvement works to be undertaken without the need for a prior remediation.

Menard designed the Dynamic Replacement to reduce the residual settlements under the exploitation loads to 25 mm with relative differential settlements limited to 1/500. The installation of the DR allowed to increase the bearing capacity beneath the footings to 200 kPa SLS. The final design comprised 1,253 DR pillars of diameter between 1.4 and 2m to 2.5 to 6m depth.

The DR have been installed over a period of 12 weeks, with 1 rig. The works have been verified through a thorough quality control, comprising post-DR CPTs, dummy foundation tests and a long duration zone load test.

Sustainable Development