An enhanced critical state sand-structure interface model considering relative density

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4. An enhanced critical state sand-structure interface model considering relative density

This study proposes an enhanced semi-hyperbolic state-dependent constitutive model for sand-structure interface. Effects of initial relative density, pile diameter and radial stress are incorporated. Recent experimental studies show that frictional resistance of piles may reduce with increasing initial relative density of surrounding soil from medium dense to dense. An optimal relative density is proposed to define the maximum shear resistance depending on the magnitude of relative density. Modifications are made to a constitutive model to include the effect of shear stress state at inflexion point on the magnitude of the shear stress at failure. The model formulation is consistent with critical state soil mechanics since the predicted void ratio changes with shear strain from the initial condition to the asymptotic critical state at large shear strains. Comparison between the model simulations and experimental data from authors previous work a wide range of initial relative densities from loose, medium dense to very dense. Results indicate that the modified model accurately predicts the behaviour of the sand-pile interface under monotonic axial load under constant normal stress as well as constant normal stiffness to adequately capture the interface surrounding boundary conditions, like those in axially loaded piles embedded in sand.

10th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE2023)

1. Constitutive modelling for saturated and unsaturated soils