Calculation on the settlement of dredged slurry treated by vacuum preloading method with consideration of clogging effects

The dredged slurry has high water content and very low strength. It is generally considered that there will be no smear effect when the PVD is inserted. However, the dense "soil column" will be formed rapidly around the PVD under the vacuum pressure, which will greatly reduce the drainage capacity and fail to consolidate, i.e. clogging. The clogging effect of vacuum preloading on the dredged slurry is studied through laboratory tests. Based on the drainage volume and rate with consolidation time in the test, the formation time and the range of clogging zone are determined by the spatial and temporal distribution of the water content and permeability coefficient of soils. A vacuum transfer mode considering the clogging effect and the time effect is proposed. At the same time, considering the nonlinear relationship between the compressibility and the permeability of soils, an analysis model for analyzing the consolidation considering the clogging effect is established and the corresponding analytical solutions are obtained. The validity of the analytical solution is verified by comparing with the existing data and field test results. The influence of vacuum transfer mode, lambda and c on the fmal settlement is analyzed by using the analytical solution in this work. The results show that the clogging effect obviously slows down the settlement rate and greatly reduces the final settlement of dredged slurry.