Amington Primary School, Tamworth

The development comprises a low-rise primary school, for Staffordshire County Council. GF Tomlinson requested Menard to submit a competitive tender for ground improvement works, as an alternative to the original piled solution, and subsequently awarded the contract to us. A Controlled Modulus Columns (CMCs) ground improvement solution was preferred by the Consulting Engineer in view of the ground conditions at this site. The structure is supported on pad foundations and a ground bearing floor slab. An SLS bearing capacity of 200 kPa was required for the pads, with a floor slab UDL of 30 kPa.

The site has had an interesting history, with a number of former uses. It lies within the boundary of the former Amington Colliery, which was in operation until it closed in the 1950s. Following this the site was used for agricultural purposes before becoming part of a golf course. A spoil mound occupied some of the proposed school footprint before being removed to create the formation for the proposed school. Ground conditions comprise deep colliery spoil (made ground) made up of medium dense to dense silty, clayey gravel, which is underlain by mudstone.

Prior to installation, a number of Cone Penetration Tests (CPTs) were drilled to supplement the available information and to provide detailed geotechnical parameters through the thickness of the made ground. Approximately 300No. CMCs were then installed to sufficient depth through the made ground to support the pad foundations and floor slabs, to achieve a performance criteria of < 25 mm total residual settlement with a relative differential settlement of <1:500. Verification of the works was carried out with plate load testing, concrete cube and slump tests. The CMC solution brought cost and programme benefits, in addition to savings in the embedded carbon footprint in comparison with the original piled solution.