Abstract: The nonlinear consolidation settlement of soft clay was mainly estimated by numerical method till now, by which the engineering application of nonlinear consolidation theory was greatly constrained. The classical nonlinear relationships, both e-lg?' and e-lgkv, were adopted in this paper, and the approximate analytical solutions with consideration of constant self-weight stress were obtained by the transformation of variables and iteration methods under case that the ratio of compressibility index Cc to permeability index Ck was not equal to 1. When the ratio of Cc to Ck approaches 1, there is little difference between the results by this solutions and that by analytical solutions with case of Cc /Ck=1. The deviation of approximate solutions from numerical solutions slightly increases with the deviation of Cc/Ck from 1 and increase in external load. When an usual external load in an actual project is considered, if the value of Cc /Ck varies from 0.9 to 1.1, the maximum deviation of this solution from the finite differential solutions varies within 2%. If the value of Cc /Ck varies from 0.75 to 1.25, the maximum deviation varies within 5%. If the value of Cc /Ck varies from 0.5 to 1.5, the maximum deviation varies within 10%. The consolidation rate decreases with an increase in the ratio of Cc /Ck in case of constant load. When Cc /Ck1, however, the consolidation rate decreases with increasing the external load.

Key words: soft soil, nonlinear consolidation, analytical solution, approximate solution, uniform distribution of self-weight