Abstract: Viscosity coefficient is a very important physical and mechanical index of soft soils. The accurate determination of the viscosity coefficient of the soft soil plays an important role in describing the creep and rheological properties of the soft soil and establishing the corresponding constitutive model. The previous methods had either limitations or disputes on their applicability, therefore, a new method to determine the viscosity coefficient is proposed by using the direct shear test according to the definition of viscosity coefficient, and the study on the influence of the shear displacement, vertical stress, consolidation, and the moisture content for the viscosity coefficient of the soft soil was investigated. The results show that the viscosity coefficient of the soft soil increases with the increase of the shear displacement and presents a logarithmic correlation; increases with the increase of the vertical stress, and presents a linear correlation; and decreases with the increase of moisture content, consolidation makes the viscosity coefficient of the soft soil larger.

Key words: soft soil, viscosity coefficient, direct shear test, moisture content, vertical stress, shear displacement, consolidation