A micromechanics based model for cemented granular materials

Cemented Granular Materials (CGMs) consist of a particle skeleton and a solid matrix partially filling the interstitial space. In this broad class we encounter a number of typical geotechnical materials such as sedimentary rocks (Sandstones, Conglomerates and Breccia) as well as naturally and artificially cemented sands. These materials, while showing a brittle behavior under shearing at low confining pressures, are ductile at high confinements. The micro mechanisms involved, that are cement disaggregation, grain crushing and fragment rearrangement, are known to be different in these two cases. Several constitutive models based on the elasto-plastic framework have been developed to describe the behavior of CGMs. However lack of correlations between the underlying failure mechanisms and the only internal variable (plastic strain), results in the use of parameters that are hard to physically identify, let alone to calibrate. In this paper, we tackle the constitutive modeling of CGMs from a more physical angle, which starts from a micro mechanical observation of grain and cement failure, to a statistical homogenization of grain scale quantities for the constitution of their continuum counterparts. In particular, while the established Continuum Breakage Mechanics approach lends itself to the description of grain crushing process, a novel definition of damage for the cement phase is introduced and shown to be measurable. The whole formulation of the new constitutive model is confined in a thermo-mechanical framework, with explicit links between the internal variables (breakage, damage and plastic strain) and the evolving microstructure of the material. As a consequence, the model possesses only a few physically identifiable and experimentally measurable parameters. The behavior of the model is assessed against experimental observations and its novel features are highlighted.Arghya Das, Alessandro Tengattini, Giang Nguyen, and Itai Eina

High spread and limited circulation of Pestivirus in wild ruminants in Spain, 2000-2017

Trabajo presentado al: . First Iberian Congress of Applied Science on Game Resources (CICARC), Abstract book pp. 76. Ciudad Real, 1-4 julio 2019