Tests with the static-dynamic dual purpose triaxial compression test apparatus which was manufactured by Hohai University and Japan Round Well Company have been completed. Through the dynamic torsional shear undrained tests on empty heart column body samples

the dynamic undrained response of the same relative density in different consolidation confining pressures is known. Effect of initial mean effective stress on the behavior is examined by tests under undrained cyclic loading at several initial confining stresses with the same stress rations. The results indicate that the stress path is not affected by changing the initial effective mean stress if the shear stress ratio remains the same.