Study On Consolidation Properties Of Dredger Fill Cofferdam With Variable Permeability

Many practical projects of dredger fill show that the settlement of soil is so great that the permeability coefficient and void ratio of a dredger fill cofferdam will change significantly in its consolidation. The consolidation results of dredger fill was obviously illogical using classical Terzaghi consolidation theory or Biot's consolidation theory with fixed consolidation coefficients. Therefore, in order to get results which reflect more exactly the process of the consolidation from the constructional to operational period, it should not only choose a reasonable model but also take varying solid parameters into account.The paper presents a research report on permeability, consolidation and intensity of four kinds of dredger fill through indoor experiments, which shows that the permeability coefficient enlarges with the increment of the void ratio, and the logarithm of the former is linear to the later. Moreover, with the same void ratio, the more sand the fill has, the larger the permeability coefficient is. Nevertheless, the permeability coefficient of the soil mixed with sand is still low compared with that of pure sand. Although the void ratio is generally monogamous to the effective stress when effective stress is large enough, the former is not linear to the logarithm of effective stress within proof stress.Based on Biot's consolidation theory and the nonlinear elastic constitutive relations of D-C, the consolidation of a cofferdam was calculated respectively using a fixed or a varying permeability coefficient according to the void ratio. The results show that the consolidation is much quicker when using the varying one. Therefore, it is very important to consider the variety of permeability in the calculation of consolidation.