Abstract: The time-rate of swelling is investigated. The variation of the consolidation coefficient in swelling process and the similarity between absorbing water and absorbing air during the process are studied through experiments. The test results show that the coefficient of consolidation keeps changing in both processes of the consolidation and swelling, ranging up to 3 orders of magnitude. The coefficient of consolidation is not a fixed parameter but a process factor which repeats in each loading and unloading. The feasibility of applying the nonlinear consolidation theory in swelling process is studied. The time-varying C_v method for consolidation and swelling is proposed, and the parameters can be obtained by fitting the experimental results. The settlement and swelling deformation obtained by the proposed method are in good agreement with the experimental results in both loading and unloading processes.