The term ‘filled ground’ is used loosely in the construction industry but it has a very specific meaning. BS5930 Code of Practise for Ground Investigations defines such ground as that ‘in which material has been selected, placed and compacted in accordance with an engineering specification’. Ground that that has been simply filled without any engineering control is termed ‘made ground’. Both types of ground are generally termed ‘anthropogenic’ as man has had an influence over both.
In most instances, anthropogenic soils derived from sampling or trial holes can be easily identified as either filled or made ground. And this is certainly the case at a property in North Cork where made ground was identified as the culprit to foundation movement in a residential property. Although the soils are clearly re-worked, a few bottles here and there prove that the soils have been made up with little or no control.
Dynamic probes show that the soils were poor to depths of 1.5m to 2.5m with refusal encountered at about 3.5m. Considering that the foundation was constructed to greater than normal parameters, it could be the case that the builder / engineer on site increased the dimensions to compensate for the poor soils. Nonetheless, it didn’t work and the proposed solution is a combination of raking micropiles through foundation and ground improvement.