Vacuum consolidation of clayey slurries with evolving heterogeneous and irregular clogging

Clogging is widely recognized as a critical factor limiting the vacuum consolidation efficiency, yet the underlying mechanisms remain insufficiently understood, particularly in horizontally drained systems where gravity induces anisotropic clogging evolution. Motivated by experimental evidence of particle relative migration and grading variation during vacuum consolidation, this study develops a two-dimensional large-strain consolidation model that incorporates heterogeneous and irregular clogging zone expansion by adopting zone-specific compression and permeability indices. The numerical solutions obtained through the alternative direction implicit scheme are verified against an established one-dimensional model for layered soil and two laboratory model tests. Parametric analyses reveal that vacuum-induced heterogeneity dominates clogging, typically causing opposite changes in compressibility and permeability in the finer (i.e., higher fines content) and coarser subsections of the clogging zone. The finer subsection adjacent to the drain generally governs and delays the overall consolidation. Irregularity of the clogging zone manifests as disparities in both maximum radius and growth rate between the vertical and horizontal directions, with the maximum radius influencing the entire consolidation process and the growth rate affecting primarily the early stages. Moreover, clogging effects are intensified by larger drain spacing, higher initial water content, or lower initial permeability.