Evolution of sedimentation rate and settlement prediction for dredged slurry under self-weight

China’s annual hydraulic dredging produces a great amount of slurry with high water content, while yard disposal usually needs several years to complete the self-weight sedimentation. It is crucial to explore the intrinsic relationship between the evolution of self-weight sedimentation rate and the initial water content (w0), the liquid limit (wL) and the initial height of slurry surface (H0) for calculating the self-weight settlement accurately. By establishing the database of slurry surface height vs. time curves derived from laboratory cylinder tests, a mathematical model for the height of slurry surface-time was developed, and the changing law of intrinsic relationship between settlement and sedimentation rate with the initial state of slurry and H0 was studied. The study indicates that the sedimentation rate firstly increases and then decreases with the increasing sedimentation time. For slurry with higher w0/wL, a higher sedimentation rate is observed at the hindered settling stage, while a lower sedimentation rate is found at the self-weight consolidation stage. The time required for completing 90% to 95% of slurry sedimentation is less than 50% of the final settlement time. Meanwhile, the degree of sedimentation completion is introduced, an empirical relationship between the initial slurry state and sedimentation rate at different degrees of sedimentation completion is established, and then a method for calculating the slurry surface settlement is proposed. The calculated values of mud surface settlement are approximately 1.0−1.1 times the measured values. This method can calculate the settlement rate at different degree of sedimentation completion according to the measured settlement-time curve, the w0 and the wL, and estimate the stable self-weight settlement quickly and accurately, which offers a quantitative analysis for optimizing the design of storage capacity.