Degradation of stiffness will occur in sand under cyclic loading. Organic matter-disseminated sand (OMDS) is a special sand in the northeast and western coastal region of Hainan Island. Through the stress-controlled dynamic triaxial test, the natural moisture content, vibration amplitude and consolidation ratio of OMDS under three types of cyclic loads (sine wave, triangular wave and rectangular wave) were studied. The results showed that the soil stiffness decreases with the increase in vibration times. The increase in natural moisture content and vibration amplitude, and the reduction in the consolidation ratio accelerate the softening of soil stiffness. Furthermore, based on the test results, an empirical formula was derived to reflect the rule of soil stiffness softening.

This study aimed to examine the aseismic performance of the pile-raft systems with various connection forms. The related shaking table test and numerical simulation were performed for in-depth investigation. The acceleration response spectra on the top of the soil layer and raft were obtained and plotted for contrastive analysis based on the model test at a reduced scale of 1 : 30 and finite element numerical simulation. Accordingly, the working mechanisms of the pile-raft systems in conventional connections with the embedment of the compressible blocks and cushion layers under cyclic loading were explored. The results showed that the embedment of the cushion layer on the pile top could most significantly mobilize the potential of the foundation soil, effectively reduce the bending moment peak of the pile, and reduce the acceleration amplification effect on the top of the soil layer and raft. The embedment of the compressible block on the pile top most markedly reduced the bending moment peak of the pile and effectively mobilized the potential of the foundation soil, which was most favorable for lowering the amplification effect of acceleration on the top of the soil layer and raft.