EFFECTS OF DEGREE OF CONSOLIDATION AND ANISOTROPIC CONSOLIDATION STRESSES ON SHEAR MODULUS AND DAMPING RATIO OF COHESIVE SOILS AT LOW STRAIN

During consolidation process of saturated cohesive soil the soil stiffness increases. Increase of the effective stress due to dissipation of excess pore pressure causes additional stiffness of soil mass. This phenomenon has a very important effect on the behavior of saturated cohesive soils during dynamic loading. In the current investigation the changes in maximum shear modulus. Gmax and damping ratio, D (as two important properties that affect on the dynamic behavior of saturated cohesive soils) at low shear strain are studied. Considering the properties of some typical soils which were used as a core of an embankment dam, a mixture of two different types of soil (SP + CL) was selected. A new resonant column system in shear mode was used in the shear strain range between? l0-6% to l0-3 %. Then the mentioned soil properties were found in two different degrees of consolidation and three different confining stresses. It is concluded that increase in the degree of consolidation causes increase in Gmax and decrease in D. These changes completely depend on the consolidation stress. The results of this study can be used to determine the dynamic behavior of the core of embankment dams during dynamic loading based on its degree of consolidation in actual cases.