An advanced constitutive model for silts and clays: a PLAXIS implementation of PM4Silt

Many constitutive models are nowadays available to simulate the mechanical behaviour of clays under different loading conditions. For geotechnical engineering applications in a soil dynamics context, the PM4Silt model, as proposed by Boulanger & Ziotopoulou (2018), can simulate the cyclic behaviour of low-plasticity silts and clays. Formulated in a bounding surface plasticity framework, this model adapts the capabilities of a previous model suited for sands and non-plastic silts, i.c. PM4Sand, and enables to simulate more clay-like soil behaviour. In this paper, published calibrations for silts with different plasticity properties are employed to simulate the experimental results of monotonic and cyclic undrained DSS test with the purpose to comment on the effect of some key parameters, including the initial stress ratio 𝐾 and the bounding surface parameter . Numerical simulations are performed with the finite element implementation of PM4Silt in PLAXIS. Besides the two original methods to define undrained shear strength (based on 𝑆􀯨 and 𝑆), a third method is proposed here based on the SHANSEP approach. The application of the model in view of the key parameters is demonstrated by means of a practical example.