Building on Clay Soils which Undergo Volume Changes

Clay soils may swell when wetted and shrink when they dry out, hence giving rise to ground movements which, depending on their severity, can cause structural damage to buildings. Loss of moisture from soil is very much influenced by transpiration from plants which, in turn, exerts a control on the suction pressure developed in the soil. The development of soil suction leads to shrinkage of the soil. When vegetation is cleared from a site prior to it being developed, its desiccating influence is removed and so the soil may swell. Empirical methods, oedometer methods and soil suction methods have been used to predict the degree to which soils swell. However, the results obtained by different methods can differ significantly. Nonetheless such results and the evidence obtained from site investigations are used to help design foundations for buildings. These vary from reinforced strip footings to rafts and bored piles, depending on the likely severity of the resultant ground movements. The soil can also be sta...