Effect of Variable Permeability Coefficient on Consolidation of Ultra-Soft Ground under Vacuum Preloading

In this paper, a soil-water coupled finite element analysis incorporated the macro-element method is carried out to investigate the effect of variable permeability coefficient on the consolidation of the ultra-soft ground using vacuum preloading. Sys cam-clay model is employed as the constitutive model of the ultra-soft soils. When the drain space becomes from 60cm to 40cm, there is significant acceleration in the numerical settlement of the ground using the constant permeability coefficient, which is quite different from the observational results. When the variable permeability coefficient where a liner relationship between the void and the logarithmic value of permeability coefficient is adopted is employed, there is a good accordance between the numerical and observational settlements. According to the distribution of variation in the void, the largest variation in the void occurs at the top several layers and therefore the predominant settlement can be attributed to the volumetric compression of the top several layers.