Abstract: Analysis on triaxial creep test data of coastal soft soil reveals that viscosity coefficient is not only related to time, but also to the deviatoric pressure and confining pressure of soil. The relation between strain rate and time is of perfect double logarithmic linear characteristics. Hence, viscosity coefficient is a power function of time. Sensitivity analysis of deviatoric pressure unveils that viscosity coefficient is linearly dependent on deviatoric pressure and exponentially on confining pressure. Last but not the least, the nonlinear relations between viscosity coefficient with time, deviatoric stress and confining pressure are established and applied to the direct shear creep test of coastal soft soil. The proposed expression is applicable to describe the variation of viscosity coefficient of soft soil with apparent nonlinear characteristics and high stress level along with time and stress. In addition, factors affecting the relevant parameters are also put forward. The research findings lay a foundation for building the nonlinear rheological model coastal soft soil

Key words: coastal soft clay, viscosity coefficient, triaxial creep, direct shear creep, nonlinear rheological model