A kinematic hardening constitutive model for sands: the multiaxial formulation

A. Gajo, D. Muir Wood

    Research output: Contribution to journalArticlepeer-review

    160 Citations (Scopus)


    This paper explores the possibility of using well-accepted concepts—Mohr-Coulomb-like strength criterion, critical state, existence of a small strain elastic region, hyperbolic relationship for representing global plastic stress-strain behaviour, dependence of strength on state parameter and flow rules derived from the Cam-Clay Model—to represent the general multiaxial stress-strain behaviour of granular materials over the full range of void ratios and stress level (neglecting grain crushing). The result is a simple model based on bounding surface and kinematic hardening plasticity, which is based on a single set of constitutive parameters, namely two for the elastic behaviour plus eight for the plastic behaviour, which all have a clear and easily understandable physical meaning.
    In order to assist the convenience of the numerical implementation, the model is defined in a 'normalized' stress space in which the stress-strain behaviour does not undergo any strain softening and so certain potential numerical difficulties are avoided.
    In the first part the multiaxial formulation of the model is described in detail, using appropriate mixed invariants, which rationally combine stress history and stress. The model simulations are compared with some experimental results for tests on granular soils along stress paths lying outside the triaxial plane over
    a wide range of densities and mean stresses, using constitutive parameters calibrated using triaxial tests. Furthermore, the study is extended to the analysis of the effects induced by the different shapes of the yield and bounding surfaces, revealing the different role played by the size and the curvature of the bounding surface on the simulated behaviour of completely stress- and partly strain-driven tests.
    Original languageEnglish
    Pages (from-to)925-965
    Number of pages41
    JournalInternational Journal for Numerical and Analytical Methods in Geomechanics
    Issue number9
    Publication statusPublished - 10 Aug 1999


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