A numerical model for the unified analysis of soil sedimentation-consolidation phenomena

Soil sedimentation and consolidation, whether they are naturally or anthropically driven processes, are closely interconnected. While theoretical models are available to separately describe the behaviour of either ‘fluid’ suspensions or ‘solid’ soil, no well-established unified theory exists able to also describe the transition effectively between the two states. In this work, a model aimed at capturing sedimentation, consolidation, and the transition between the two phenomena via a simplified ‘interaction coefficient’ [1], [2] was revised and applied to the simulation of relevant engineering problems using finite element software COMSOL Multiphysics. Finite kinematics to reproduce the evolution of large strains was modelled using a Lagrangian coordinate framework. The numerical model was applied to the simulation of experimental results from the literature, including deposition tests involving uniform suspensions of both fine- and coarse-grained soil and backfilling sedimentation tests of a sand-water mixture. In particular, the simulation of backfilling tests required the definition of a bespoke numerical strategy to reproduce the injection of the sand-water mixture in Lagrangian coordinates. The numerical modelling framework developed in this work may be efficiently used in the analysis of a number of engineering applications concerning sedimentation and consolidation, including industrial problems where a suspension must be separated into solid and fluid components, and offshore geotechnical problems involving submarine pipeline trench backfilling and land reclamation.