Constitutive modeling the undrained behaviors of sands with non-plastic fines under monotonic and cyclic loading: Fid-Bau Portal

Constitutive modeling the undrained behaviors of sands with non-plastic fines under monotonic and cyclic loading

Xu, Ling-Yu / Zhang, Jing-Zhe / Cai, Fei / Chen, Wei-Yun / Xue, Ying-Ying

Abstract In recent years, some unified critical state compatible (UCSC) frameworks have been established for constitutive modeling of both clean sand and sand with various quantities of fines. In existing UCSC frameworks, the equivalent granular void ratio e ^* and equivalent granular state parameter ψ ^* are used instead of the void ratio e and state parameter ψ to define the soil state and density state, respectively; this enables existing UCSC frameworks with the capability of constitutive modeling of sands with various quantities of non-plastic or low-plasticity fines using a unique set of model parameters. However, existing UCSC frameworks cannot be applied to cyclic loading. This study proposes a UCSC framework by merely substituting e ^* and ψ ^* for e and ψ into the equations of a stress-ratio controlled state-dependent plasticity model that includes cyclic loading simulation capabilities. The proposed UCSC framework is implemented in a fully coupled dynamic effective-stress finite element procedure. The simulative capability of the proposed UCSC framework is evaluated by comparison of the model predictions with existing experimental data of triaxial tests under monotonic and cyclic loading. Moreover, the effects of the fines content on the cyclic resistance ratio and the characterization of liquefaction susceptibility of sandy soils are investigated.

Highlights • A UCSC framework is proposed to model the undrained behaviors of sand with non-plastic fines under both monotonic and cyclic loading. • The cyclic resistance ratio of sandy soils CRR 15 can be well correlated with the equivalent granular state parameter of sandy soils ψ ^* . • ψ ^* could provide a more reasonable characterization of liquefaction susceptibility of sandy soils than the equivalent granular void ratio of sandy soils e ^* . • Different bases used for the comparison of clean sands and fines-containing sands is proved to result in conflicting conclusions for the effect of the fines content on liquefaction resistance. • The effects of b values on the cyclic liquefaction strength and the data points in $e^{*} - \log p^{'}$ space and on the number of cycles to reach liquefaction are clarified.