Microstructural observations of clayey soils indicate that clay particles are aggregated in units of low internal porosity (microporosity). Larger voids (macroporosity) between those units are associated with the flow of free water. Within this context, the secondary deformation of clay is interpreted as being a consequence of local mass transfer of water from the micropores to the macropores. The capability of a model based on this idea to reproduce the effects of loading history on the secondary compression of clay is explored. An experimental test program has been performed, secondary compression records have been interpreted within the proposed theoretical framework, and material parameters have been derived. The simulation of additional validation tests has been successful. The theory and model developed provide a unified framework for compression, as well as swelling secondary deformation.

Peer Reviewed