Numerical simulation of cyclic shear tests considering the fabric change and principal stress rotation effects

Abstract

Cyclic loadings could induce complicated soil responses, including the fabric change and principal stress rotation, both of which would reduce the effective confining pressure and accelerate the build‐up of excess pore water pressures, thus leading to sand liquefaction in undrained conditions. The principal stress rotation, even without the change of principal stress magnitudes, would further generate the accumulative plastic shear strains. However, most of the existing studies focus on their individual effect and the combined effect was seldom considered. In this paper, a numerical approach including an elastoplastic sand constitutive model is proposed to consider the combined effect of the fabric change and principal stress rotation. In this model, the fabric change is considered with the anisotropic critical state theory and the principal stress rotation is considered by splitting the plastic strain increment into the monotonic part and rotational part. By simulating a series of cyclic shear tests, results from the numerical solutions are found showing good agreements with the existing experimental results and the importance of considering the combined effect is demonstrated. The approach can be used to predict the stress‐strain response of sand and guide the design of foundations especially in undrained cyclic loading conditions, for example, earthquake loadings conditions.

Modified unified critical state model for soils considering over-consolidation and cyclic loading behaviours

“…First, soil behaviour is assumed to be isotropic in this paper for the sake of simplicity. If the inherent and induced anisotropy behaviours of soils need to be considered, CASM-kII may be extended to account for anisotropy by incorporating anisotropic mechanism such as rotational hardening behaviour 30 – 35 or soil fabric and its evolution rule 36 – 39 in the model. The extension work for the issue of anisotropy can be referred to the work of Gao et al 40 Second, the bold-faced characters are used to represent vectors and tensors and the italics are used to represent scalars.…”

Poroelastic response of unsaturated soils to cyclic loads with arbitrary waveforms

“…We emphasize that all settlements calculated in this example, by the assumption of poroelasticity, are elastic settlements and do not include inelastic settlements, see Refs. 55–59.…”