Experimental study on consolidation of dredged sludge by grouting flocculation-vacuum preloading method considering influences of soil salinization

To address the issues of poor permeability and long consolidation time of dredged sludge, the flocculation-vacuum preloading method has been widely employed to treat such soil. For the existing soft soil foundation, a combined method that integrated grouting flocculation and vacuum preloading was proposed. The indoor model tests were conducted on the dredged sludge with varying initial water contents where different lime contents were controlled. The changes of the pore water pressure, displacement and settlement were monitored. The pH, salinity, water content and vane shear strength of soil were measured after the tests. The optimal lime content, considering the influence of strength growth and soil salinization, was determined for the grouting flocculation-vacuum preloading. Then the efficacy of the combined method was further verified through its application in Longwan Phase Ⅱ coastal wetland restoration project. The results of this study can be used as a design reference for the applications of the combined method in other similar projects.