The effects of tree roots on the electrical properties of triassic clay

A large percentage of housing in England is built on clay foundations, where clay shrinkage and swelling can lead to building subsidence and heave that result in insurance claims. As volumetric change due to absorption of water into clay mineral structure is a characteristic of some clay minerals, it follows that buildings situated on clay geology may be susceptible to heave and subsidence. This may be strongly amplified if trees are in close proximity, as root-induced changes in moisture content will also cause volumetric changes. The problem of clay and root induced subsidence really became recognised in the UK in the 1970s after the drought of 1975 and 1976 that affected the whole of North-western Europe (Driscoll 1983).