Characteristics and predictions of accumulative deformation of structured soft soil under long-term cyclic loading

To address the long-term settlement of embankments over structured soft soil during the in-service stage, artificial structured soils with different interparticle bonding strengths and initial void ratios were prepared, and repeated triaxial loading tests were conducted to investigate the effects of bonding strength, initial void ratio, stress amplitude and cycle number on the accumulative deformation characteristics. The results show that the relationship between the accumulative plastic strain and cycle number can be classified into stable, critical and destructive types, and an empirical relationship between the stress sensitivity and dynamic stress ratio is established. Furthermore, two different empirical models for accumulative plastic strain are presented that incorporate soil structure. Reasonable agreement between the model predictions and the experimental results for different natural soft soils demonstrate that the proposed models can accurately capture the accumulative deformation behaviour of structured soils. In addition, considering the accumulated plastic deformation of soil subjected to cyclic loading as static creep, a simplified method for calculating three-dimensional cyclic accumulative deformation is proposed by implementing the proposed model in a finite-element simulation utilizing an implicit stress integration algorithm. Finally, the effects of the dynamic stress level and structural strength on the accumulative deformation are analyzed. This has important implications in controlling the long-term settlement of embankment in soft soil area.