MEDIGRA · Mechanics of Energy Dissipation in Dense Granular Materials

Granular materials are of interest to different fields of the physical sciences and engineering. To model their behaviour, either a solid- or fluid mechanics approach is used. Rather than deforming uniformly, granular fluids develop thin shear-bands, which mark areas of flow, material failure and energy dissipation. The MEDIGRA project proposes a thorough experimental, theoretical and numerical study of the Mechanics of Energy DIssipation in dense GRAnular materials. The fundamental challenge faced by the project is to quantify the various energy dissipation mechanisms in dense granular materials using innovative thermo-poromechanical experiments. The measured characteristics are expected to lead to the formulation of appropriate analytical and numerical tools aimed to describe the mechanical behaviour of granular materials from the rigorous angle of energetics. In particular, the project proposes to: 1) Design, develop, install and exploit a novel Thermographic High Speed Cylinder Shear Apparatus (THSCSA) to study the properties of the mechanical and thermal boundary layer that is forming at the inner rotating-drum material interface, as well as determining the required thermographic properties of granular materials. 2) Convincingly quantify the way the total energy dissipation is split into heat production, grain breakage and other mechanisms, using the project-developed THSCSA apparatus and other advanced experimental apparatuses. 3) Develop physical models and robust numerical tools capable of incorporating the experimentally obtained dissipation characteristics. 4) Test the knowledge acquired within the project in two applications (shear segregation and landslide modelling). The project aims to advance our knowledge on the basic physics behind long-standing open problems such as the “heat-flow paradox” in earthquake mechanics, the lifetime prediction of imminent catastrophic landslides and the applicability of continuum approximations to segregation phenomena.