Undrained multi-dimensional deformation behavior and degradation of natural soft marine clay from HCA experiments

Abstract

In actual engineering, cyclic loading, such as wave loading, multi-directional seismic loading, and traffic loading, involves the continuous rotation of the principal stress axis in the ground. A series of consolidated-undrained torsional shear tests was performed on large, hollow cylindrical specimens, using a hollow cylinder apparatus (HCA), to investigate the undrained deformation behavior and degradation of natural soft marine clay from Wenzhou, China. The test results obtained from this study showed that the undrained response of saturated marine clay was strongly influenced by the cyclic stress ratio (CSR) and the effective confining pressure under continuous principal stress rotation, in terms of the axial strain, the axial and torsional stress–strain hysteretic loops, stiffness degradation, and the resilient moduli. In this study, the cyclic stress ratio was CSR = qcyc/p′, where cyclic stress qcyc is σz-σθ and p′ is the initial effective confining pressure. Axial and torsional degradation indexes were refined according to the tests. Empirical formulas for the axial and torsional resilient moduli under continuous principal stress rotation were presented.