The soil static and dynamic universal triaxial and torsional shear apparatus recently facilized in Dalian University of Technology is employed to perform experimental tests on flyash with relative density of Dr = 60 % under three-directional anisotropic consolidation subjected to cyclic torsional shear loading. Through a series of soil tests

the effects of initial intermediate principal stress coefficient on dynamic shear modulus and damping ratio of medium-dense fly ash are investigated systematically. Based on the specialty of the apparatus

not only the precision of experiment can be improved by using the small angle displacement sensors and large angle displacement sensor installed in the triaxial cell

but also the whole changes of dynamic modulus and damping ratio with amplitude of dynamic shear strain can be obtained continuously.