THM coupling analysis for slurry dewatering improved by thermo-promoted vacuum preloading: A finite-strain model with variable stress-temperature paths

Unlike conventional methods that integrate heating and drainage in a single drain element, thermo-promoted vacuum preloading (TPVP) is a more field-applicable dewatering strategy by decoupling heat input from vacuum drainage. In this context, a new finite-strain model is developed to capture the thermo-hydro-mechanical (THM) coupling response during TPVP-assisted dewatering. The coupled interactions between nonlinear consolidation and heat transfer under variable stress-temperature paths and various practical factors are incorporated. The coupled governing equations are then derived and solved with alternating direction implicit finite difference method, with accuracy confirmed through degenerative analysis and experimental comparisons. Parametric analysis indicates that heating efficiency declines nonlinearly with increasing heating range due to extended conduction paths. Additionally, intermittent cyclic heating induces periodic fluctuations and longer cycles yield higher peak temperatures, and staged loading schemes reduce the peak excess pore water pressure (EPWP) but retard the consolidation rate. Temperature elevation accelerates the dissipation of EPWP and increases ultimate settlement, with beneficial effect being further amplified under staged loading. A full-length heat source produces uniform and accelerated temperature rise, while thermal dissipation across semi-thermally insulated boundaries remarkably attenuates energy efficiency. Finally, heating partially alleviates impeded drainage from smear zone expansion and limited permeability of prefabricated vertical drains.