Large-Strain Consolidation of Sludge in Geotextile Tubes Considering Vacuum-Induced Rapid Consolidation and Soil Reconstitution

Clogging represents a crucial factor severely hindering the vacuum preloading treatment for clayey sludge. However, the underlying mechanism of this occurrence remains insufficiently investigated, limiting the application of this treatment technique. In this study, a two-dimensional large-strain consolidation model is developed to elucidate the dewatering process of dredged sludge in vacuum-assisted geotextile tubes, incorporating the key contributors to clogging: rapid consolidation (i.e., initial state mutation) and soil reconstitution (i.e., particle grading evolution). Numerical solutions obtained utilizing the alternative direction implicit difference method are verified against an established one-dimensional model for layered soils and two laboratory model tests. Parametric analyses reveal that the rapid consolidation-induced reduction in initial permeability and void ratio facilitates consolidation, while soil reconstitution-induced inhomogeneity in grading impedes the process. Compared to the compression index Cc, the permeability index Ck affects the consolidation more significantly in terms of soil final state and treatment efficiency. Furthermore, the increasing rate and growing pattern of the clogging area slightly affect the consolidation process in the early stages, and greater deformation can be achieved by decreasing the spacing of prefabricated horizontal drains and increasing the tube filling height.