Ground Improvement Alternatives for a New Build on Made Ground – Staffordshire Joint Cadet Centre

SWJ Consulting designed the foundations and structural engineering solutions for a new multi-million-pound Joint Cadet Centre in Staffordshire, developed on the site of a former car park. The sustainable new facility will provide modern training accommodation for Army Cadet Force and Royal Air Force Air Cadet units within the region, creating a multi-purpose centre for cadet training and community use.

Foundations on made-ground

One of the principal engineering challenges of the project was the presence of made ground across the site. The site was also constrained by nearby gas mains, requiring careful consideration when considering vibration, excavation depths, and construction methods during the design process. Traditional foundation solutions would have required deep excavations or piled foundations, both of which would have increased programme costs and additional construction risks.
Sustainability Considerations

The new single-storey masonry building was designed with sustainability at its core and aimed to achieve the Ministry of Defence’s DREAM (Defence Related Environmental Assessment Methodology) Excellent standard. Sustainability features included a simple building form to minimise heat loss, roof-mounted solar panels with battery storage, air source heat pumps, heat recovery ventilation systems, and high-performance insulation with triple-glazed windows throughout.

SWJ Consulting assessed a number of foundation options and proposed two viable solutions: traditional piled foundations with reinforced ground beams, or a ground improvement solution using a vibro-improvement techniques.

What is Vibro Compaction

Vibro compaction is a ground improvement technique used to densify weak or variable soils commonly found on reclamation and made-ground sites, increasing their load-bearing capacity and improving overall ground stability. The process uses powerful horizontal vibrations to rearrange and compact loose soil. As the surrounding soil consolidates, a crater naturally forms at the surface, which is back-filled with gravel or sand. This creates compacted stone columns within the ground, strengthening the soil around the columns and providing more stable ground.

Vibro-compaction crane on site – image courtesy of WMRFAC

Ground improvement to reduce waste and carbon footprint

Following detailed evaluation, the contractor selected the vibro-improvement solution, enabling shallow reinforced strip foundations to be constructed above the water table while significantly reducing excavation depths, minimising waste material and its removal.

Additional monitoring of the nearby gas mains was completed throughout the ground improvement works to ensure everything proceeded safely. The chosen solution delivered both sustainability and efficiency by reducing the amount of concrete needed, the amount of spoil that needed to be removed and the transport needed to do so.

Structurally, the building comprised load-bearing masonry walls supporting large timber roof trusses over what can effectively function as a modern drill hall space. Due to the height of the masonry walls and the extensive glazed sections within the elevations, SWJ Consulting carefully considered the building’s lateral stability to ensure the structure performed safely under wind loading and other horizontal forces.

Working closely with SC Architecture Ltd, Seddon Construction, and the wider project team, SWJ Consulting carried out periodic inspections and attended regular site meetings to ensure the project progressed smoothly and met both the client’s engineering and sustainability objectives.

The completed development shows how innovative ground improvement techniques can provide cost-effective and sustainable alternatives to traditional piled foundation solutions on challenging brownfield sites.

Images used courtesy of WMRFAC

If you have a similar project that you might need some advice on, then give SWJ Consulting  a call on 01993 225085 (Witney, Oxfordshire) or 02381 920656 (Southampton) or email mail@swjconsulting.co.uk