Using the electro-dynamic type shaking table, we carried out eight series of test on dry sand layers under different conditions made in the box on the shaking table with 5m long, 1.5m wide and 1.5m high.
　The sand layers used in the experiment are following : horizontal sand layers with 80, 60, 40 cm thick, respectively, in the loose state and 75 cm thick in the dense state, and truncated wedge-type sand layers with 125cm high in the loose state and in the dense state, respectively.
　The sand is fine grained sand called Onahama sand with the effective size of 0.13mm, the uniformity coefficient of 1.31 and the angle of repose of 32.5゜.
　In any constant acceleration level of the table, the frequency was changed from 0.2 cps to 100cps and a table acceleration and the accelerations in some places of the sand layer were measured by the unbonded type wire strain gage accelerometers.
　Acceleration responses of dry sand layers were obtained from recorded data.
　The obtained acceleration responses of dry sand layers show that the vibrations of sand layers consist of many vibration systems and have some characteristics depending upon the non-linear stress-strain relation-ship of sand layers.
　As the first approximation, we assumed that the vibrations of sand layers could be represented by the shear vibration at any constant accleration level of the table. By applying the theory of shear vibration to the obtained acceleration responses, we estimated the shear wave velocities and damping constants of dry sand layers.
　From a result of the experiment on dry sand layers, the following facts were made clear.
　Firstly, in the very small deformation (strain range within about the shear wave velocity of dry sand layers is about 170 m/sec in the dense state and about 100 m/sec in the loose state.
　Secondly, as the deformation of the sand layer increases, apparently, the shear wave velocitie of the sand layer decreases and the damping constant of the sand layer increases.
　Thirdly, the vibrations of sand layers are less influenced by the walls in the direction of the table motion, but in the transverse direction, they are much influenced.