Stress–dilatancy behavior of dense marine calcareous sand under high-cycle loading: An experimental investigation

Calcareous sand is an important filling material in marine engineering. The accurate interpretation of the calcareous sand's stress–dilatancy behavior under high-cycle loading can help improve the long-term stability of marine reclamation infrastructures. In this study, drained monotonic and high-cycle triaxial tests were conducted on calcareous sand and siliceous sand. Results show that the stress–dilatancy behavior of calcareous sand under high-cycle loading differed significantly from that under monotonic loading. Due to the continuous adjustment of the internal structure and state parameter (ψ) during cyclic loading, the number of loading cycles (N) has a considerable effect on the stress–dilatancy behavior of calcareous sands. As N increases, the stress–dilatancy of dense calcareous sand gradually transforms from loading-induced contraction and unloading-induced dilation to loading-induced dilation and unloading-induced contraction. A phase transition state line of calcareous sand under long-term cyclic loading is found in the e-(p/pa)0.7 plane, where its gradient is insignificantly influenced by the initial state, whereas its intercept depends on the initial pressure. Furthermore, a correlation between the number of loading cycles and the flow rule considering the state parameter (ψ) was proposed to describe the direction of strain accumulation for calcareous sand.