Unsaturated soils will undergo deformation as ground is soaked or underground water table rises. The increase in water content can result in

on one hand

compression due to rise in specific weight of soil

and

on the other hand

rebound due to decrease in matric suction. The comprehensive effect is controlled by these two types of factors. Based on generalized Hook’s law of elasticity

Fredlund’s theory of two stress state variables and the empirical relationship between matric suction and saturation given by Brooks and Corey

an incremental-type of constitutive model is established for unsaturated soils loaded under the condition of K0- consoilidation. Combined with the layer-wise summation method; the proposed model can be used to assess deformation of unsaturated soils induced by the soaking of ground

rise or lowering of water table as well as over-evaporation. The proposed method is used to assess vertical deformation of a soil stratum as an example. It is displayed that deformation characteristics of the unsaturated soil is not only dependent on soil properties

but also associated with the variation of profile suction distribution and thickness of soil layer as well as stress states. The procedure can also be used to evaluate the settlement of footing on unsaturated soil foundation.