Effect of a vacuum gradient on the consolidation of dredged slurry by vacuum preloading

In this paper, a large-scale indoor model test was carried out to reinforce dredged slurry by vacuum preloading, and the effect of the vacuum gradient on the reinforcement effect was studied. The vacuum pressure, volume of extracted water, average ground settlement, and excess pore-water pressure were monitored during the test. After the test, the water content and vane shear strength were measured, and a particle analysis test and a scanning electron microscopy test were carried out. The results indicated that a small vacuum gradient could improve the consolidation degree and strength of the soil, and the smaller the vacuum gradient, the better the reinforcement of the soil. In addition, reducing the vacuum gradient could decrease the differential settlement of the soil surface and alleviate the migration of fine particles to the prefabricated drainage plates; therefore, the small vacuum gradient improved the clogging of the prefabricated drainage plates and the uniformity of soil consolidation. However, reducing the vacuum gradient also extended the test period. A vacuum gradient of 20 kPa obtained the fastest consolidation rate of the soil.