Experimental Study On Dynamic Behavior Of K₀ Consolidated Saturated Clay

The dynamic characteristics of saturated clay are nonlinear,hysteretic and cumulative,and are mainly affected by the cyclic stress history and the initial stress conditions,etc.In this paper,the development rules of cumulative shear strain,dynamic shear modulus and damping ratio are studied by a series of K₀ consolidated undrained cyclic triaxial compression tests of saturated clay.The octahedral shear stress of soil elements,when destroyed,are taking as normalized parameters,and the static deviatoric stress and cyclic shear stress acted on soil elements are expressed as octahedral static deviatoric stress ratio and octahedral cyclic shear stress ratio.the relationship of cumulative octahedral shear strain with static deviatoric stress ratio,cyclic shear stress ratio and cyclic number was established through K₀ consolidated cyclic triaxial test under one confining pressure.Using the cumulative octahedral shear strain as state parameters to capture the cyclic stress history,and the maximum dynamic shear modulus,G_max,of different state parameters can be obtained from experiments.The curves of normalized shear modulus,G/G_max,relation to octahedral cyclic shear strain was obtained in different static deviatoric stress and different cyclic shear stress under one confining pressure,compared to the results of normalized shear modulus with shear strain results under other two confining pressure,the relationship of dynamic shear modulus with cyclic shear strain can be obtained through cyclic triaxial tests of a confining pressure and multistage cyclic triaxial tests of three confining pressure under different cumulative strain,and the relationship of the maximum shear modulus with octahedral cumulative shear strain and the effective volume stress after consolidation of soil element is obtained.Therefore,if the the effective volume stress after consolidation of soil element and the octahedral cumulative strain are known,the maximum shear modulus can be determined,and then the relationship between shear modulus and cyclic shear strain is determined according to the normalized shear modulus and the cyclic shear strain curve.The relation curves between the damping ratio and the cyclic shear strain are obtained by fitting cyclic triaxial test results under a confining pressure,which are close to the?-?experimental results in different confining pressure,different static stress and different cumulative strain conditions.That is,though the relationship between the damping ratio and the cyclic strain obtained by cyclic triaxial test under a confining pressure,the unique relationship between the damping ratio and the cyclic strain is predicted under different confining pressure and the static deviatoric stress condition.