A water retention model for deformable soils

The paper presents an experimental study on water retention behaviour of two reconstituted soils, a silty clay (Speswhite kaolin) and a sandy clayey silt ( Barcelona silt) and two compacted soils, a silty clay ( Speswhite kaolin) and a silty sandy gravel (Adige river embankment). These soils were used with the aim of encompassing a wide range of soil types and soil fabrics. Specimens were subjected to drying and wetting 'hydraulic' paths by removing or adding water under zero total stress and to 'mechanical' wetting paths by compressing specimens at constant water content. To investigate a broad range of void ratios, the reconstituted sandy clayey silt was initially reconstituted from slurry by applying different consolidation vertical stresses, whereas the compacted Speswhite kaolin and Adige river embankment were compacted to a broad range of water contents and compaction energy. On the basis of the experimental data, a modification to the van Genuchten's model is proposed to account for the effect of void ratio on 'main drying' and 'main wetting' behaviour. The model is based on parameters having clear physical meaning and can properly describe water retention at medium and low degrees of saturation. It is formulated in such a way that effect of void ratio on 'scanning' behaviour can potentially be accounted for. The model applies to both the compacted and reconstituted soils investigated in this programme and describes water retention behaviour regardless of whether the degree of saturation is changed in a mechanical or hydraulic fashion.