Modeling of Shakedown Accumulation of Secondary Deformation of Granular Soils Subjected to Low-Amplitude High-Cycle Loading

The progressive accumulation of secondary deformation, occurring incrementally under lowamplitude, high-cycle loading in soils, can lead to significant displacement of foundations. This study has developed a novel phenomenological model to describe the shakedown accumulation behavior of secondary deformation in granular soils subjected to low-amplitude, high-cycle loading. Firstly, gradual densification of granular packing yields an average volume strain that obeys a logarithmic law as the cyclic loading persists. A log-hyperbolic function, constrained by a limit, is reasonable, considering that the strain will reach a steady state of finite value as the cycle number approaches infinity. Secondly, cyclic loadings with average stress induce the accumulation of strain in the direction of average stress as the cycle number increases. This has been incorporated into the well-known modified Cam-clay model. Lastly, the proposed model has been calibrated using data obtained from undrained and drained cyclic triaxial tests conducted on uniformly fine-grained sands. The results suggest that the model effectively exhibits important features of the accumulation of both volumetric and deviatoric deformation induced by drained cyclic loading over a large number of cycles.