Numerical Simulations of Cone Penetration Response via Accounting for State-Dependence and Full-Strain-Range Non-Linearity of Sand
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The penetration response of CPT is not only related to the stress and density states of sand but also influenced by the non-linear stress-strain relations of soils from very small (10-5) to relatively large (10-1) strain levels. Appropriate considerations of the above key soil behaviours can be crucial for accurate numerical simulations of CPT response. For this purpose, an intergranular strain (IGS)-based elastic model is introduced into a critical-state-based, state-dependent plasticity model to capture the state-dependence and full-strain-range non-linearity behaviour of sand. A numerical model of the CPT penetration process is then established by combining the aforementioned constitutive model and the arbitrary Lagrangian-Eulerian (ALE) large deformation finite element technique. The latter is adopted to handle the problems of large deformations of soil and mesh distortion. Then the computed response of CPT is compared against centrifuge test observations, and the numerical model is utilized to analyse the influences of the full-strain-range non-linearity behaviour of sand on the penetration response of CPT. The results indicate that the non-linear stress-strain relations at small strains can have noticeable impacts on the tip resistance of CPT, in particular for loose sand, while having a relatively small influence on the penetration depth required to reach a steady-state penetration resistance. The above influences might be attributed to a rapid decay of soil strains with the distance from the cone tip, and consequently high stiffness and strong constraints effects of far-field soils on core soils adjacent to the cone tip.