Seismic velocity and shear-wave splitting under cyclic loading

To study the change law of seismic velocity and shear- wave splitting with cyclic loading, used Autolab 2000 petrophysical testing system which was introduced from USA, experiment measured seismic velocity of quartz sandstone sample from Yangzhuang, Jixian, under the confining pressure (5-150MPa) of different cycles. Got the change law of compressional wave velocity and shear wave velocity with the changing confining pressure, and then analyzed the shear-wave splitting. Preliminary results showed that seismic velocity of unload is higher than the seismic velocity of load. P wave velocity of the second cycle is lower than the corresponding P wave velocity of the first cycle when the confining pressure is lower than 50MPa and S wave velocity of the second cycle is higher than the corresponding S wave velocity of the first cycle. When the confining pressure is under 60MPa, shear-wave splitting of unload is lower than the corresponding shear-wave splitting of load and shear-wave splitting of the second cycle is lower than the corresponding value of the first cycle.