Coupled modeling for simultaneous prediction of consolidation settlement and contaminant transport in heavy metal-laden sediments during vacuum-assisted dewatering process

Dredged marine sediments combine high water contents with environmental risks, and vacuum preloading with prefabricated vertical drains (PVD-VP) offers a scalable dewatering strategy. Notably, the dewatering-induced fluid seepage may facilitate the contaminant migration and removal, while the relevant transport mechanisms remain insufficiently explored. In this context, a new large-strain model is established to simultaneously predict consolidation and contaminant transport during the vacuum-assisted dewatering. Then the governing equations are solved with ADI finite difference approach, with validation achieved through degeneration analysis, case studies and finite element comparisons. Furthermore, parametric analysis reveals that initial contaminant concentration profiles profoundly shape the spatiotemporal evolution of contaminants, with exponential distributions exhibiting marked tailing effects that prolong clean-up in deeper layers. By increasing hydraulic resistance and extending flow paths, the reduction in PVD drainage capacity, larger PVD installation spacing and expanded smear zone significantly retard the consolidation process while impeding contaminant removal efficiency. Moreover, vertical seepage within soils will become progressively more influential in governing drainage and transport when the influence zone enlarges. Taken together, the proposed model demonstrates the dual role of PVD-VP in dewatering and remediation from the theoretical perspective.