Abstract: The consolidation coefficient is not a constant in the process of soft-soil consolidation. The variation regularity of consolidation coefficient is related to engineering properties of soil, preconsolidation pressure and effective consolidation stress. When the consolidation stress is less than the preconsolidation pressure ( ), the consolidation coefficient decreases with the increasing of consolidation stress. When the consolidation stress equals to the preconsolidation pressure ( ), the consolidation coefficient takes the minimum value. When the consolidation stress is greater than the preconsolidation pressure ( ), the consolidation coefficient of silt increases with the increasing of consolidation stress. There is an apparent double logarithmic linear correlation between consolidation coefficient and consolidation stress(ln( or )- ) of Wenzhou silt. The fitting formula is a piecewise function according to the preconsolidation pressure( ). The variation regularity of consolidation coefficient during soil consolidation gotten by improved Kadota method further illustrates and verifies the expression presented. The consolidation coefficient of silt during the entire loading procedure could be calculated by the double logarithmic fitting formula accurately, which provides the important parameter for the consolidation settlement calculation.

Key words: silt, consolidation coefficient, consolidation stress, preconsolidation pressure