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The dynamic interaction between granular flowing masses and obstacles is a very complex phenomenon involving large displacements and high strain rates. To simulate the event in a continuum-based framework both advanced numerical tools and constitutive relationships are required. In this work, the impact of a dry granular mass against a rigid wall is numerically simulated using the open-source Material Point Method code ANURA3D, while the constitutive model proposed by Marveggio et al., 2021 is adopted for the granular mass. The model accounts for rate and grain packing dependence, which have been shown to be crucial to reproduce the propagation of compression and rarefaction waves inside the mass. The model is capable of reproducing “solidification” and “liquefaction” phenomena observed in the DEM impact tests results already available in the literature.

The use of numerical codes for simulating the propagation phase of fast landslides requires the definition of constitutive relationships suitable for the description of the mechanical behaviour of granular soils, under both solid and fluid conditions. In this paper, the authors briefly illustrate a constitutive modelling approach interpreting the material as a bi-phasic continuum, according to which the solid phase may behave like a solid, under quasi-static conditions, and a fluid, under collisional/dynamic conditions. The model presented seems to satisfactorily reproduce a series of results obtained by using a discrete element numerical code on mono and polydisperse granular specimens. The constitutive model has been implemented in a Material Point Method code to solve boundary value problems, in which strain rate large values are expected to influence the material response.