Abstract: A vacuum consolidation model equipment is designed for performing a series of vacuum consolidation tests on two dredged clays with different liquid limits reconstituted at different initial water contents. The experimental results indicate that the ratio of the initial water content to the liquid limit is a useful dimensionless index for describing the behaviour of fine particle migration of dredged clays under vacuum pressure. It is found that there is a unique critical value of the ratio of the initial water content to the liquid limit for the occurrence of particle migration. When the ratio of the initial water content to the liquid limit is less than the critical value, the particle migration of dredged clays does not occur under vacuum pressure. But in the case that the ratio of the initial water content to the liquid limit is larger than the critical value, the particles of dredged clays migrate to the drainage surface, resulting in the enrichment of clay particles in the vicinity of the drainages. The level of clay particles enrichment increases with the increase in the ratio of the initial water content to the liquid limit.