Finite-strain modelling of PVD-assisted consolidation in clayey soils using a novel elastic–viscoplastic model with destructuration based on the equivalent time concept

Prefabricated vertical drains (PVDs) are widely adopted to accelerate the consolidation of clayey soils. However, long-term settlement during the service period of infrastructure is often not adequately captured when soil structure degradation and creep are neglected. Existing models rarely consider the coupled effects of soil destructuration, creep, and nonlinear water flow in PVD-assisted consolidation. This study develops an axisymmetric finite-strain consolidation model incorporating an elastic–viscoplastic model with structuration (EVPS) based on the equivalent time concept. The formulation is applicable to clays possessing inherent structure that may undergo structure degradation under mechanical loading or PVD installation. The model considers soil creep, destructuration, smear effects, and nonlinear water flow, and is solved using an alternating direction implicit (ADI) finite-difference scheme. Finite-element comparisons are employed solely to verify the numerical implementation of the consolidation equations. Model performance is evaluated through comparisons with laboratory oedometer tests on natural structured clays and long-term field observations from the Haarajoki embankment. The results indicate that the proposed model can consistently reproduce pore-pressure dissipation and settlement evolution, including deformation occurring after primary consolidation over periods of several years to decades. Parametric studies reveal that soil destructuration, smear effect, and non-Darcian flow jointly govern the consolidation process. The proposed model enables more reliable prediction of consolidation behaviour in natural structured clays, which is essential for assessing long-term settlement and supporting rational design of ground improvement schedules. • A novel EVPS constitutive model based on the equivalent time concept captures coupled creep and destructuration in structured clays. • EVPS model is embedded in an axisymmetric finite-strain consolidation model with nonlinear permeability and compressibility. • An ADI finite-difference scheme is formulated and verified against FE simulations demonstrating reliability numerically. • Model performance and parametric responses are evaluated by laboratory tests, field observations, and systematic analyses.