Geotechnical Engineering

Desiccation in cohesive soils

The roots of all vegetation can take moisture from the soil. In a clay soil this may result in drying and shrinkage of the soil and subsidence in the ground which may result in damage to buildings. Removing a tree may result in ground re-hydration, which will cause a clay soil to swell, resulting in ground heave which may also cause damage to buildings.

The potential for desiccation can be initially identified during the phase 1 desk study, through a review of historical information or from the site reconnaissance visit.

An intrusive investigation will enable the classification of soils through the use of in-situ and laboratory techniques to provide a quantitative estimate of the depth and degree of any potential desiccation. This may be useful to help determine whether damage has been caused by subsidence due to clay shrinkage, to estimate the potential for heave and help develop an appropriate solution through design such as underpinning or foundation design advice, suitable for the new construction.