Validation of a new soil constitutive model for cyclic loading by FEM analysis

Nowadays, there is an increasing need to understand the behaviour of geotechnical structures during earthquakes. The damage caused by the recent earthquakes has shown that the local geology and the geotechnical characteristics of the foundation soil can influence significantly the seismic response of structures. So, in order to correctly predict the behaviour of a structure subjected to an earthquake, it is necessary to focus attention on the dynamic soil behaviour. In general, very simple soil constitutive models are implemented in commercial codes. Several studies have shown that when shear strains in the soil are small, it is possible to use the elastic-linear model; for medium strains it is convenient to use equivalent linear or nonlinear models. Elastic-plastic models, incrementally nonlinear models or hypoplastic models can more accurately capture response for sites that experience higher strains. A recent elasto-plastic constitutive model including both isotropic and kinematic hardening has been implemented in a FEM code. The numerical results achieved by the new version of the FEM code, are discussed and validated by means of the comparison with laboratory experimental results involving sands of different relative densities. An interesting parametric analysis is also presented, in order to investigate the effects of the implemented constitutive model parameter variation in the soil cyclic behaviour.