Cyclic behavior of saturated soil: a new 3D model

The role of pore pressure cannot be neglected for saturated soils in a strong earthquake, which is characterised by a large amplitude and duration. Indeed, pore water pressure controls phenomena such as cyclic mobility and liquefaction due to the loss of soil strength and stiffness. This can lead to a fast decrease of effective stresses and permanent deformations in the soil causing severe damage to structures. Motivated by experimental observations, a plasticity model is developed for capturing the main characteristics of cyclic mobility. This model extends an existing multi-surface plasticity formulation and is based on the relationship between the pore pressure and the shear work. The three-dimensional stress state of the material is considered. The proposed model allows to model the effect of cyclic loadings on saturated soils and to assess the multidirectional effect. Comparison between the modelling results and the experimental ones from triaxial and torsion tests are made to show the validation and the capacity of the current model.