Abstract

This paper presents a large-strain implementation of the SIMSAND on the Geotechnical Particle Finite Element Method (G-PFEM). SIMSAND is a simple, critical-state-based constitutive model, which captures the density and pressure dependent behaviour of sands. The formulation adopts a large-strain hyperelastic–plastic framework that employs the Kirchhoff stress tensor and the Hencky strain tensor instead of their small-strain counterparts. Local integration is performed using a multiplicative decomposition of the deformation gradient and an explicit integration scheme with substepping error control adapted to large strain. Global convergence is enhanced through the IMPLEX scheme and a non-local regularization to alleviate mesh dependence during strain-softening dominated simulations. The implementation is validated through drained and undrained triaxial simulations using both single-Gauss-point element tests and boundary-value problems. Comparation with experimental data for Fontainebleau sand NE34 shows that the model successfully reproduces contractive and dilative behaviour, as well as peak and post-peak softening. The resulting framework provides a robust tool for modelling large deformation geomechanical problems, with planned applications to cone penetration test and pile installation in sands.