Undrained deformation behavior of marine clay under two-way cyclic loading

In offshore engineering, marine clays, which are widespread in the southeastern coastal areas of China, may be subjected to two-way cyclic stresses. To experimentally investigate the effects of the two-way cyclic stress with low-stress amplitude on the cyclic behavior of soft marine clay, a series of triaxial tests is performed on intact marine clay from Zhoushan covering various values of the cyclic stress ratio (CSR) and confining pressure (p′0). Several useful conclusions are inferred: First, the double-amplitude axial strain (εDA), dynamic axial modulus (E), and energy dissipation (W) increase with the CSR. Second, under the same CSR, the value of εDA is independent of p′0. The values of E and W increase with increasing p′0 during cyclic loadings, whereas the normalized modulus and normalized energy are independent of p′0. Third, an allowable CSR is proposed based on the strain behavior and energy concept. Based on the experimental results, two equations are established to predict the dynamic axial modulus and double-amplitude axial strain.