Model tests on vacuum preloading technology of super-soft soil

The reclaimed land is formed by use of the super-soft soil with water content of 80%. With the development of land reclamation, the thickness of the reclaimed soil becomes thicker and thicker, so that great deformation occurs during the vacuum preloading. The vane test strength reaches about 40 kPa in the surface of the foundation after vacuum preloading in the field, but below the depth of 3-4 m, the vane strength only reaches about 10 kPa. Through the model tests, it is found that the Prefabricated vertical drain PVD has undergone a drastic distortion because of large deformation of the soil, which leads to the PVD efficiency decrease, so that the soil reinforcement is ineffective. And it can not meet the foundation design requirements. The PVD is installed for the second time to make secondary reinforcement to the soil after the deformation of the reinforced soil reached stabilization. The results show that the settlement of the soil developes further, that the water content of the soil decreases further, that the vane strength can be further improved, and that the diminishing rate of the vane strength along the depth is greatly improved. The result shows that the secondary reinforcement can improve the effect of the vacuum preloading. The study provides a basis for exploring a more effective method to reinforce deeply reclaimed soil.