Study on dredged slurry improvement via top-bottom vacuum preloading: time ratio effect

Conventional vacuum preloading is widely used for dredged slurry treatment, but vacuum pressure loss often leads to inadequate bottom consolidation and uneven reinforcement. This study proposes a vacuum preloading method with top-bottom drainage and investigates its consolidation performance and the influence of time ratio (i.e. bottom-to-top vacuum application time) via laboratory model tests. Overall, the proposed method achieves better consolidation than conventional vacuum preloading, with higher drainage, larger settlement, lower post-treatment water content and improved vane shear strength of dredged slurry. Time ratio greatly affects consolidation efficiency, and the optimal ratio is 1:1. At this ratio, the proposed method raises the average vane shear strength by 14.4% and reduces post-treatment water content by 6.0% compared with conventional vacuum preloading. Results demonstrate that top-bottom drainage vacuum preloading enhances vacuum pressure uniformity, promotes water discharge, and achieves more effective and uniform consolidation of dredged slurry.