I am using plaxis2D to study the effect of downdrag on the pile capacity due to soil liquefaction.
The liquefied soil is about 20 ft below ground surface. I used Mohr-Coulomb model for the liquefied soil for first three phases (including initial phase, phase 1 and phase 2). In phase 4, i switched the Mohr-Coulomb model to the soft soil creep model for the same liquefied soil layer to perform the consolidation analysis. Is it correct?
Thanks,
Dear Wanxing Liu,
Mohr-Coulomb model (i.e. linear elastic model coupled with Mohr-Coulomb failure criterion) has limited ability to simulate the response of soil under cyclic loading, particularly when causing liquefaction. Among other aspects, Mohr-Coulomb model is not able to reproduce reduction in stiffness and the concurrent increase in hysteretic damping with strain amplitude, the occurrence of phase transformation and onset of liquefaction. Moreover, it has also limited ability to capture the effect of initial state on the response of soil.
In PLAXIS 2D, we have two standard constitutive models (UBC3D-PLM and PM4sand models) particularly developed to address the simulation of cyclic response of sand, including when subjected to liquefaction-related phenomena. In PLAXIS 3D, UBC3D-PLM model can be employed. For clay, a hypoplastic model can be employed. In principle, the aforementioned constitutive models are able to capture the post-shaking response of sand (in other words, can be employed to the simulation of consolidation phase).
Regarding Soft Soil Creep model, it has been particularly developed to simulate the response of normally-consolidated (or lightly overconsolidated) clay, particularly when it is important to account for a time-dependent response (i.e. creep effects).
For more case-specific questions, please submit a service request: https://apps.bentley.com/srmanager/ProductSupport.