Abstract: The penetration response of cone penetration test (CPT) depends on the stress and density states of sand and is also influenced by the non-linear stress-strain relations of soils from very small (10−5) to relatively large (10−1) strain levels. Accounting for these key soil behaviours is crucial for accurate numerical simulations of CPT responses. For this purpose, an intergranular strain (IGS)-based elastic model is introduced into a state-dependent plasticity model to capture the 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 with 1g 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. Furthermore, this paper explores the strong constraint effects of far-field soils through the analysis of the cavity expansion problem, highlighting the significance of full-strain-range non-linearity of sand in addressing large deformation issues related to deep compression failure.

Key words: sand, cone penetration test(CPT), numerical simulations, state-dependent constitutive model, small strain stiffness