Improved Vacuum Preloading Method Combined with Sand Sandwich Structure for Consolidation of Dredged Clay-Slurry Fill and Original Marine Soft Clay

An improved vacuum preloading method combined with a sand sandwich structure (SSS) was developed to facilitate the consolidation of dredged clay-slurry fill and original soft marine clay for land reclamation. In this method, a novel sandwich structure is formed as a sand layer introduced on to original soft marine clay prior to the placement of reclaimed, dredged clay-slurry. This assists in transmitting the vacuum pressure to both the reclaimed, dredged clay-slurry and the original soft marine clay, through prefabricated vertical drains, with little vacuum loss, and the sand layer thereby improving the efficiency of the vacuum preloading. Field pilot tests were carried out on improved ground both with and without using a SSS in order to demonstrate the capacity of the improved vacuum preloading method combined with the SSS. Field measurements were performed to evaluate the ground settlement, degree of vacuum loss, effective consolidation stress, shear strength, and bearing capacity. The test data showed that better consolidation results were achieved using the improved vacuum preloading method combined with the SSS