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 cause 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.

The 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 potential desiccation. The investigation will determine whether damage has been caused by subsidence due to clay shrinkage; estimate the potential for heave and help develop an appropriate solution; or provide foundation design advice suitable for the new construction.