Cyclic response of natural soft marine clay under principal stress rotation as induced by wave loads

- Continuous principal stress rotation is used to simulate wave loads by HCAs.
- The influence of CSRs and confining pressures on pore water pressure, cyclic strain and dynamic modulus etc. are discussed.
- A new critical value is suggested under principal stress rotation.

In order to investigate the cyclic deformation behavior of natural soft marine clay under the general stress condition, which is due to travelling waves involved principal stress rotation, a series of undrained tests were carried out by using GDS hollow cylinder apparatus (HCA). The principal stress axis rotates continuously while holding the deviator stress (difference between the vertical normal stress and horizontal normal stress) at a constant level. The tests results show that, the pore water pressure, stress-strain hysteretic loop, dynamic modulus of the tested samples are significantly dependent on CSRs and confining pressures. Furthermore, pore water pressure generates slightly during the first 30 cycles, and accumulates with the increase of cycles. The tensile axial strain occurs in the initial loading cycles and the development styles are various with different CSRs and confining pressures. With the larger CSRs and confining pressures, higher strain degradation occurs. A new critical value between 0.16 and 0.18 is suggested for CSR under continuous principal stress rotation.