Experimental Study on Shear Strength Characteristics of Soft Soil on Wetland in Cold Regions

To solve the problem of stability of soft soil foundation of highway on wetland in cold regions under incremental loading during construction of subgrade or embankment and to provide necessary parameters for study on stability of soft soil foundation on wetland in cold regions by theoretical calculation method,undisturbed soil samples were collected and triaxial test and direct shear test were carried out for two-layer soft soil of wetland in cold regions to study the change of relation between the main stress difference and axial strain under five different consolidation pressures and three different degrees of consolidation as well as the change of shear strength indexes and shear strength under five different consolidation pressures and six different degrees of consolidation.The results of triaxial test show that(1)in undrained shear test,the relation between stress and strain of the first layer of soft soil appears in typical work hardening characteristic,while the relation between stress and strain of the second layer of soft soil is similar to perfect plasticity;(2)under a fixed strain,deviatoric stress increases gradually with increase of consolidation pressure and degree of consolidation.The results of direct shear test show that(1)shear strength increases with increase of consolidation pressure and degree of consolidation;(2)cohesive force c decreases with increase of degree of consolidation when degree of consolidation U is less than 20% but generally increases with increase of degree of consolidation when degree of consolidation U is larger than 20%;(3)the internal friction angle φ increases a little bit with increase of degree of consolidation,but the law of change is not obvious.