Reinforcement Effect of the Stepped-Alternating Vacuum Preloading Method on Dredged Fills

Dredged fills have been widely used as a filling material to meet the demand for land resources during land reclamation in coastal areas. When the conventional vacuum preloading (CVP) method is used to reinforce dredged fill foundations, clogging and accumulation of a dense silt layer significantly reduce the lateral soil permeability of the soil surrounding prefabricated vertical drains (PVDs), leading to a poor reinforcement effect. To address these issues, this paper presents a laboratory model study to evaluate the reinforcement effect of a new method, the stepped-alternating vacuum preloading method (SAVP), in comparison to the CVP method. A series of laboratory model tests were conducted to compare the results of the new SAVP method and the CVP method. The model tests used water discharge, discharge rate, and surface settlement to compare both methods. Additionally, vane shear strength and moisture content were measured after reinforcement. This study evaluates the performance of the SAVP method and proposes an optimal preloading pattern that demonstrates best performance in delaying clogging formation and alleviating the accumulation of a dense silt layer on the surface of the PVDs.