Constitutive modeling of unsaturated soils using a refined suction-controlled cubical test cell: Final observations

Results from a comprehensive series of suction-controlled hydrostatic compression, conventional triaxial compression, triaxial compression, triaxial extension, and simple shear tests, conducted on several statically compacted specimens of poorly-graded sand with clay, were used to calibrate and further validate two of the most popular elasto-plastic critical state based frameworks postulated to date for unsaturated soils, namely, the Barcelona Basic Model (BBM) and the Oxford Model (OM). The experiments were accomplished in a newly developed true triaxial apparatus suitable for testing cubical, 7.62 cm (3 in) side, specimens under controlled-suction states and for a wide range of stress paths that are not readily achievable in a cylindrical cell. The apparatus is a refined version of the one previously reported by Hoyos et al. (2008). In general, predictions of unsaturated soil response from either model are shown to be reasonably accurate, highlighting their potential for use in computational analyses of geotechnical boundary-value problems that involve geosystems made of compacted soil or resting on unsaturated ground.