During earthquakes

the shear wave can be simulated by the horizontal bidirectional shear stresses mutually coupled in magnitude and direction. To investigate the influence of cyclic shear stress ratio (SSR) and phase difference on dynamic characteristics of soft clay under bidirectional loading

19 groups of undrained cyclic simple shear tests have been performed on typical Wenzhou soft clay by using multi-direction cyclic shear apparatus. The test results show that the threshold cyclic stress ratio SSRx

menkan for the typical Wenzhou soft clay under unidirection cyclic shear loading is 0.096 and the critical cyclic stress ratio SSRx

limit is 0.15. Under the bidirectional cyclic shear loading

the increase of cyclic number N and the improvement of SSR will promote the development of shear strain and pore pressure u. When SSR is slightly larger than SSRx

menkan

the increase of will decrease the development of and u. When SSR is between SSRx

menkan and SSRx

limit

shear strain and pore pressure u increase rapidly with the increase of . When SSR is larger than SSRx

limit

the effect of phase difference on the shear strain and pore pressure u can be ignored.