A Unified Framework for Unsaturated Hydraulic Behavior of Widely-Graded Soils

The microporosity structure of a soil provides important information of hydraulic conductivity and soil–water characteristics of the soil, as described in Chaps. 3 and 5. The microporosity structures of fine soils may change significantly during wetting and drying (Simms and Yanful, Can Geotech J 38:741–754, 2001; Cuisinier and Laloui, Int J Numer Anal Meth Geomech 28:483–499, 2004; Boivin et al., Soil Sci Soc Am J 68:1145–1153, 2004; Braudeau et al., Soil Sci Soc Am J 68:359–370, 2004). Such variations of soil microporosity structures are inherently related to the drying and swell/shrinkage behavior of the soil (Ferber et al., Eng Geol 104:200–210, 2009; Aung et al., Geotech Geol Eng 19:401–416, 2001) and are the main difficulty in establishing quantitative relations between soil fabric and soil shrinkage/swell behavior.