Abstract
The suction-control techniques commonly used for laboratory studies of mechanical behaviour of unsaturated soils are much more time consuming than standard soil mechanics tests. In addition, few laboratories have the required apparatus for testing unsaturated soils. This paper proposes an alternative method of analysing hydromechanical behaviour of unsaturated soils with high-porosity. The method is divided in three tasks: 1) verification of the effect of void ratio changes on the water retention curve using filter paper; 2) determining water content changes by evaporation under the same test conditions; and 3) performing saturated and unsaturated consolidation tests. Unsaturated tests make use of samples that are less than 100% saturated and there is no suction control during the test. Therefore, only initial water content is known. Significant suction changes take place due to void closure and evaporation while testing. The results obtained using the proposed methodology showed the stress and suction path and enhance the understanding of the hydromechanical behaviour of unsaturated soils. The results also showed that analyses of water content alone cannot explain some unexpected results, such as: 20% initial water content samples present less deformation than 16% samples.
Highlights
The study of unsaturated soil mechanics has shown great progress in recent decades due to the need to solve practical engineering problems such as designing and maintaining foundations, pavements, dams, embankments, and canals subject to varying degrees of saturation during construction as well as during the design lifetime.Paradigms have changed significantly
Modern testing techniques for characterization of soil microstructure have led to studies of hydromechanical behaviour of unsaturated soils based on microstructural characterization and constitutive models coupling these three aspects (Gens & Alonso, 1992, Alonso et al, 1999 and Alonso et al, 2011, Alonso et al, 2013)
It is normally assumed that water content remains constant during consolidation tests with initial water content known, sample suction may thereafter be evaluated
Summary
The study of unsaturated soil mechanics has shown great progress in recent decades due to the need to solve practical engineering problems such as designing and maintaining foundations, pavements, dams, embankments, and canals subject to varying degrees of saturation during construction as well as during the design lifetime.Paradigms have changed significantly. Afterwards, several more recent papers have examined their interaction, i.e., mechanical and hydraulic behaviour coupled (Vaunat et al, 2000; Wheeler et al, 2003; Sheng et al, 2004, Della Vecchia, et al, 2012). Modern testing techniques for characterization of soil microstructure have led to studies of hydromechanical behaviour of unsaturated soils based on microstructural characterization and constitutive models coupling these three aspects (Gens & Alonso, 1992, Alonso et al, 1999 and Alonso et al, 2011, Alonso et al, 2013). Characterizing and obtaining constitutive parameters of unsaturated soils is time-consuming and testing and acquisition of equipment with suction control techniques, using advanced technology that is not available at most geotechnical laboratories, can be costly
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