Measuring and upscaling micromechanical interactions in a cohesive granular material

Abstract

The mechanical properties of a disordered heterogeneous medium depend, in general, on a complex interplay between multiple length scales. Connecting local interactions to macroscopic observables, such as stiffness or fracture,...

Failure processes of cemented granular materials

“…We will now explore how the failure of the cohesive granular material under compression is affected by its initial packing fraction, focusing on simulations between φ = 0.350 and 0.580. In a related study incorporating experimental findings [47], we also describe how changing bond stiffness affects the elastic response of this type of material. The presentation and discussion of results will progress from the elastic response of the system at low strains, through to the statistical features of the micro-crack assembly as yielding begins, and finally to the modes of failure seen at different φ.…”

“…Therefore, we have designed DEM simulations where the various elastic responses of the components (e.g. spring constants) are constrained by the measurements of micro-mechanical experiments involving two glass beads connected by an isolated polymer bridge [47]. Although we focus on information from one particular set of experiments (see Table I), this modeling method can be extended to any similar cohesive granular material by suitably choosing these material constants.…”

“…To simplify the simulation parameters, we also nondimensionalize our model using this particular set of experimental parameters [2,3,47]. Specifically, we scale the system such that the average mass (m) and diameter (D) of the particles, along with the spring constant for normal glass-glass contact (k glass n ) take on unit values.…”

“…For this we use an average particle diameter of 200.9 µm and an average particle mass of 10.8 µg. The k glass n is set ten times higher than the normal spring constant of a polymer bridge, where the latter is estimated as 5.76 kN/m [47]. This ratio is low enough to prevent numerical instabilities, yet high enough to capture the difference of stiffness between the glass beads and their softer bonds.…”

“…From such microscopic experiments, the effective spring constants of the polymer bonds are extracted. Based on these information, one can model a cohesive granular media through a DEM [46] simulation and reproduce the macroscopic experimental results primarily in the elastic regime, including the effects of bond stiffness [47].…”