Influences of cyclic stress paths on deformation behavior of saturated marine coral sand: An experimental study

The deformation of foundations in saturated marine coral sand induced by dynamic loading such as that from waves, earthquakes, tsunamis, and hurricanes is a key factor endangering the safety of marine engineering. However, the deformation characteristics of coral sand in the marine environment are complex and have rarely been studied. A number of undrained cyclic shear tests are performed with saturated coral sand under various consolidation conditions and cyclic stress paths. The results show that the medium-dense coral sand specimens exhibit two deformation failure modes: plastic strain accumulation and cyclic mobility. A novel method for cyclic strain path is presented to characterize the progressive development of cyclic deformation, and an important finding is that the difference between the cumulative plastic component and cyclic component at 5% deviator strain can be used to distinguish between the deformation failure modes. Another finding is that the parameter lambda related to deviator strain rate and cyclic loading frequency can be used to distinguish the deformation failure modes. A relationship between complex stress conditions and deformation failure modes is established based on analyzing the major and minor principal stress. The proposed method provides new insights into the mechanics of deformation failures in saturated coral sand.