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An Improved Cap Model for Partially Saturated Soils
Soils consist of a porous soil skeleton filled by fluids like air and water. The accurate description of their mechanical behaviour requires a coupled solid-fluid approach. The analysis is based on a set of balance equations for mass and momentum, kinematic equations and constitutive equations, the latter including a material model for partially saturated soils. In this contribution we present a constitutive model for partially saturated soils developed as an extension of the cap model proposed by Kohler and Hofstetter (2008). The elasto-plastic model is formulated in terms of two independent stress variables, generalised effective stress σ*ij and matric suction pc. The yield surface includes a shear failure and a hardening cap surface. The evolution of the yield surface in terms of matric suction is controlled by the load collapse (LC) yield curve and parameters defining the suction-dependent intersection of the shear failure envelope with the I*1-pc-plane, where I*1 = tr(σ*ij). We introduce an improved LC yield curve to enable a better representation of wetting/drying paths and to allow a smooth transition from partially to fully saturated state. An efficient and reliable projection algorithm is proposed for determining the stresses and internal variable at the integration point level. It includes the solution of separate scalar nonlinear equations for the hardening cap and the shear failure surface. Numerical results for a silty sand are in good agreement with experimental data.
An Improved Cap Model for Partially Saturated Soils
Soils consist of a porous soil skeleton filled by fluids like air and water. The accurate description of their mechanical behaviour requires a coupled solid-fluid approach. The analysis is based on a set of balance equations for mass and momentum, kinematic equations and constitutive equations, the latter including a material model for partially saturated soils. In this contribution we present a constitutive model for partially saturated soils developed as an extension of the cap model proposed by Kohler and Hofstetter (2008). The elasto-plastic model is formulated in terms of two independent stress variables, generalised effective stress σ*ij and matric suction pc. The yield surface includes a shear failure and a hardening cap surface. The evolution of the yield surface in terms of matric suction is controlled by the load collapse (LC) yield curve and parameters defining the suction-dependent intersection of the shear failure envelope with the I*1-pc-plane, where I*1 = tr(σ*ij). We introduce an improved LC yield curve to enable a better representation of wetting/drying paths and to allow a smooth transition from partially to fully saturated state. An efficient and reliable projection algorithm is proposed for determining the stresses and internal variable at the integration point level. It includes the solution of separate scalar nonlinear equations for the hardening cap and the shear failure surface. Numerical results for a silty sand are in good agreement with experimental data.
An Improved Cap Model for Partially Saturated Soils
Gamnitzer, P. (author) / Hofstetter, G. (author)
Fifth Biot Conference on Poromechanics ; 2013 ; Vienna, Austria
Poromechanics V ; 569-578
2013-06-18
Conference paper
Electronic Resource
English
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