Abstract
The performance of a recently developed state-dependent constitutive model for unsaturated granular soils is evaluated. The model employs the Bounding Surface plasticity framework and evaluates elastic strains assuming hyperelastic behavior. To realistically simulate the deformation of unsaturated granular soils, the mechanical behavior was modeled without a purely elastic component. The inherent hydro-mechanical coupling was realized by introducing a Bishop-type effective stress, an appropriate work-conjugate variable, and a soil-water characteristic curve function. Relevant details about the model development, parameter estimation, and the assessment of the model’s predictive capabilities are presented. The model performance is evaluated with experimental data obtained for drained and constant-water stress paths. With a given a set of parameter values, the model realistically simulates the main features that characterize the shear and volumetric behavior of unsaturated granular soils over a wide range of matric suction, density, and net confining pressure. This is found to be true for both drained and constant-water stress paths.
Highlights
Environmental conditions control the depth of the groundwater table and, the thickness of the unsaturated soil zone; i.e., the zone between the ground surface and the water table
Research in this field was pioneered by Alonso et al [3], who extended the modified Cam-Clay model [4] to develop an elasto-plastic model based on the concept of two independent stress state variables
In Equation (1), pnet is the net confining stress, s is the matric suction, χ is the Bishop effective stress parameter, Sre is the so-called relative degree of saturation, Sr is the degree of saturation, and Sr0 is the residual state degree of saturation, which can be estimated from the soil water characteristic curve (SWCC), and the symbols represent Macaulay brackets
Summary
Environmental conditions control the depth of the groundwater table and, the thickness of the unsaturated soil zone; i.e., the zone between the ground surface and the water table. Based on the concept of two stress state variables, several constitutive models were subsequently developed and used to simulate the behavior of unsaturated soils [e.g., 6, 7, 8]. A state-dependent constitutive model that can describe the mechanical behavior of granular soils is assessed for performance under different stress paths. The model is an extension of an existing hyperelastic model, which was originally proposed by Lashkari et al [25] for simulating the elastoplastic behavior of fully saturated granular soils. In this model, elastic strains are computed from the Gibbs free energy. The model’s performance is assessed by comparing its simulations with experimental data for clean sand following drained and constant-water stress paths
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