DYNAMIC EFFECTIVE SHEAR STRENGTH OF SATURATED SAND

The dynamic effective shear strength of saturated sand under cyclicloading is discussed in this paper.The discussion includes the transient time depen-dency behaviors based on the analysis of the results obtained in conventional cyclictriaxial tests and cyclic torsional shear triaxial tests.It has been found that the dy-namic effective shear strength is composed of effective frictional resistance and viscousresistance,which are characterized by the strain rate dependent feature of strengthmagnitude,the coupling of consolidation stress with cyclic stress and the dependencyof time needed to make the soil strength sufficiently mobilized,and can also be ex-pressed by the extended Mohr-Coulomb’s law.The two strength parameters of thedynamic effective internal frictional angle φd and the dynamic viscosity coefficient ηare determined.The former is unvaried for different number of cyclic loading,dy-namic stress form and consolidation stress ratio.And the later is unvaried for thedifferent dynamic shear strain rate γt developed during the sand liquefaction,butincreases with the increase of initial density of sand.The generalization of dynamiceffective stress strength criterion in the 3-dimensional effective stress space is studiedin detail for the purpose of its practical use.