Post-cyclic undrained shear behavior of marine silty clay under various loading conditions

The post-cyclic undrained shear characteristics of marine silty clay was investigated by conducting a series of cyclic triaxial tests on undisturbed specimens. The effects of confining pressure, initial undrained shear stress ratio (qs/p0), cyclic stress ratio (qcy/p0) and number of cycles (N) on the post-cyclic undrained shear behavior were investigated. Results show that the post-cyclic shear strength decreases with the increase in qs/p0, qcy/p0 and N. The confining pressure has no apparent effect on the normalized post-cyclic monotonic undrained shear strength for the silty clay. During the post-cyclic shear, the specimens with small qs/p0 and qcy/p0 contract, while the cases with large qs/p0 and qcy/p0 dilate. Also, the terminal value of normalized post-cyclic shear-induced excess pore pressure decreases with qs/p0 or qcy/p0 increasing. The Equivalent Hvorslev Line (EHL) was proposed to form a failure envelop for the post-cyclic silty clay and the slope of EHL increases with the increase in qcy/p0 or qs/p0, regardless of the number of cycles. Moreover, a post-cyclic strength model, which could consider the influence of initial shear stress and previous cyclic loading history was proposed on the basis of Yasuhara model. This model demonstrates a good agreement with the test results.