Experimental study on stress relaxation characteristics of soft dredger fill under UU triaxial shear

Stress relaxation often occurs in the saturated soft clay with poor water permeability under the actual working condition at fast construction speed (fast loading rate), which brings huge hidden dangers to the safe operation of engineering practice. Herein, the unconsolidated undrained triaxial shear test was performed based on the soft dredger fill in Tianjin Binhai using the WF stress path triaxial instrument, and the influence law of such factors as the different initial strain, confining pressure, shear rate, sampling depth and structural properties of the soft dredger fill on its stress relaxation characteristics was analyzed accordingly. According to the test results, the stress relaxation process of soft dredger fill in coastal region of Tianjin under different test conditions can be divided into the fast, slow and stable stages. The rate of stress relaxation increases with the increasing initial strain and sampling depth, but slightly affected by the confining pressure and shear rate. Besides, the enhancement of soil structure will significantly increase the rate of stress relaxation, thus exacerbating the stress relaxation. Moreover, it is determined through comparative analysis that the power function model is more suitable to describe the change law of stress relaxation of soft dredger fill under different test conditions. Generally, the research results have important practical significance for the safe construction and operation of soft dredger fill site in coastal region of Tianjin.