Abstract: Mechanism of Stress relaxation differs from creep in their mechanism, and they can not be simply exchanged. Consolidated undrained triaxial shear test(CU) can simulate many operating conditions containing a certain degree of stress relaxation. Engineering accidents caused by stress relaxation sometimes occur. Tianjin Binhai soft dredger fill has significant rheological properties. In this study, soft dredger fill was tested by triaxial-shear tests to examine the stress relaxation behavior of the soil samples under consolidated and undrained conditions. The results show that the stress relaxation process can be divided into rapid stage, slow stage and stable stage. Within a certain range, the stress relaxation rate increases with the increasing of initial deviator strain relaxation. there exists an approximate linear relationship between deviatoric stress and logarithmic time. Stress relaxation has little effect on the total shear strength index while decreases the effective cohesion and increases the effective angle of internal friction . Finally, a model for stress-strain-time relationship reflecting the stress relaxation characteristics of dredger soft fill is deduced and validated through fitting and normalizing the test data. This research has supplemented the rheological properties of Tianjin Binhai dredger soft fill, and can provide a theoretical reference for the prevention of related engineering accidents.

Key words: soft dredger fill, triaxial shear, stress relaxation, relaxation rate, empirical model