Expandable and straw-woven drains for dredged slurry with intermittent vacuum preloading

This study proposes a consolidation method combining expandable drainage systems – both synthetic and straw-woven – with intermittent vacuum preloading, addressing limitations inherent to conventional vacuum preloading techniques such as the formation of low-permeability soil columns and diminished drainage efficiency at later consolidation stages. Laboratory model tests were conducted to investigate the effectiveness of this approach using this expandable drainage system, where the effect of radial strain amplitude of the expandable drain was evaluated. Results indicate that strain-induced microcracks can enhance soil permeability by forming dual (pore-crack) drainage pathways that improve vacuum transmission and drainage efficiency. Compared with conventional constant vacuum preloading, the proposed approach achieved up to 29.5% greater cumulative water discharge, increased vane shear strength by up to 33.1%, and reduced post-consolidation differential settlements. In addition, straw-woven drains were tested as environmentally friendly alternatives. Despite minor performance reductions due to material degradation, straw drains exhibited comparable consolidation efficiency, achieving 87.1%–94.5% of the performance metrics of synthetic expandable drains. These findings reveal the feasibility and engineering potential of the proposed method for improving the consolidation of dredged slurries.