A New Isotropic Hyper-Elasticity Model for Enhancing the Rate of Convergence of Mohr-Coulomb-Like Constitutive Models and Application to Shallow Foundations and Trapdoors

A new hyper-elastic formulation is proposed for improving the convergence of Mohr–Coulomb-like constitutive models at small stresses, when the convergence problems come from the vicinity to the apex of the yield surface and the elastic predictor can lay in a region in which the yield surface is not defined. The proposed hyper-elastic formulation avoids stress states with tensile mean pressures and provides shear and bulk stiffnesses increasing with the square root of mean stress, as typically occurs in granular soil. The new model is applied to two typical engineering problems: a centred-loaded, superficial foundation and the active and passive trapdoor problem. The numerical results are compared with upper and lower bound solutions, showing the reliability of FEM results. In addition, FEM analyses highlight some peculiar aspects of soil-foundation interaction which are usually neglected in the current engineering practice of foundation design.