Cone penetration test study of ultra soft soil after vacuum preloading

No sand cushion vacuum preloading method is one of the construction technology for treating the ultra soft soil formed with hydraulic fill at present. The practice is ahead of the scientific research work, as the effect detection technology of the surface-layer improvement is still in the stage of exploration. In this paper, the cone penetration test (CPT) is used to detect the effect of the surface-layer improvement of the ultra soft soil based on one case in Zhejiang province in China. The result shows that the cone tip resistance is at the range of 0.08 similar to 0.40MPa and the thickness varies about 1.5 to 2.2 m of the treated ultra soft soil. The cone tip resistance along the depth has two kinds of curve shape and four zones.