| Abstrakt: |
Studies about the strain-softening behavior of unsaturated soils published in the literature during the past three decades are summarized under three categories; namely: (i) mechanical characteristics and micromechanisms, (ii) prediction models for shear strength, and (iii) numerical methods for modeling strain-softening behavior of unsaturated soils. In addition, the influence of the soil–water characteristic curve and time effects on the strain-softening behavior of unsaturated soils are discussed. Various experimental studies related to the strain-softening behavior of unsaturated soils are summarized to interpret the mechanical behavior characteristics and micromechanisms of the strain-softening under large shear deformation. The widely used empirical/semi-empirical prediction models from the literature for interpreting the peak, critical, and residual shear strength of unsaturated soils are comprehensively summarized considering the influence of soil fabric and water phase on the shear strength. Several numerical methods (i.e., conventional plasticity, bounding surface plasticity, disturbed state concept, and elasto-viscoplasticity) of modeling the strain-softening behavior of unsaturated soils are discussed, highlighting their strengths and limitations. The comprehensive details summarized in this paper related to the strain-softening behavior is valuable for the rational analysis and design of geostructures in unsaturated soils that undergo large shear deformation. In several scenarios, unsaturated soils exhibit strain-softening behavior when they undergo a large deformation during the shearing stage. In other words, there is reduction in the shear strength from a peak to a residual value associated with the evolution of a shear band where the dilation is localized. Shear deformations behavior in geo-infrastructures constructed in unsaturated soils are sensitive to the wetting conditions associated with rainfall infiltration. Therefore, shear strength in the geostructures varies between peak and residual value according to the magnitude of corresponding shear deformation. For this reason, the strain-softening behavior should be considered for reliable analyses and design of geo-infrastructure in unsaturated soils undergoing large shear deformation. This paper provides a comprehensive review of the studies about the physical mechanisms and numerical modeling methods of strain-softening behavior of unsaturated soils. The contents summarized in this article assist geotechnical engineers to understand how the strain-softening occurs in unsaturated soils under shearing, and how the shear strength reduction due to strain-softening behavior can be modeled in engineering practice applications. [ABSTRACT FROM AUTHOR] |
