Abstract:

With the development of land reclamation, the seabed elevation level becomes lower and lower and the thickness of the reclaimed soil reaches 10 m from 2 m original; so that great deformation occurs during the vacuum preloading. The strength of a soil layer about 2 m to 3 m in the foundation surface is high after the vacuum preloading in the field, but below the depth of 3 m to 4 m, the strength of soil increases little. Through super-soft soil vacuum preloading model test, it is found that the PVDs have undergone a drastic distortion because of big deformation of the soil, so that the PVDs efficiency becomes lower and the soil reinforcement is ineffective. The PVDs are installed for a second time and made secondary reinforcement to the soil after the deformation of the reinforced soil reaches stabilization. The results show that the settlement of the soil develops more; the water content of the soil can be lowered further; the vane strength can be improved more; and the diminishing rate of the vane strength along the depth is greatly reduced. It is shown that the efficiency of PVDs reduces due to the deformation in the first installation; and it can not meet the foundation design requirements; using secondary PVDs installation can have better reinforcing effect. The study results provide basis for exploring a more effective method to reinforce deep reclaimed soil.

Key words: super-soft soil, vacuum preloading, model test, drain efficiency, secondary PVDs installation