Discrete particle simulation of particulate systems: A review of major applications and findings

Adequacy of approximation of ellipsoidal particles composed of a set of sub-spheres for numerical Discrete Element Method (DEM) simulations is examined. The algorithm of adaptive hierarchical multi-sphere (MS) model is suggested for composing elliptical particles. Numerical simulation of the piling problem is used as a test problem for evaluating the adequacy of MS model approximation in comparison to the model of smooth ellipses for multiparticle system. The accuracy of MS approximation with the increasing number of sub-spheres is examined in detail by comparison of macroscopic and microscopic parameters of granular dynamics. It was determined that the data on macroscopic parameters yielded by the MS model tend to converge to those of the smooth ellipsoid with the increasing number of the constituent sub-spheres, and the MS model approximates the smooth perfect ellipsoid with a reasonable number of sub-spheres within the limits of the appropriate tolerance. It can be concluded that a multi-sphere model remains a realistic and relatively simple particle model applicable to DEM simulations of the behaviour of the real smooth and rough elliptically shaped particles.

Investigation of adequacy of multi-sphere approximation of elliptical particles for DEM simulations

The rheological behavior of non-cohesive soils results from the arrangement and complex geometry of the grains. Numerical models based on discrete element modeling provides an opportunity to understand these phenomena while considering the discrete elements with a similar shape to that of the grains the soil is composed of. However, dealing with realistic shapes would lead to a prohibitive calculation cost. In a macroscopic modeling approach, simplification of the discrete elements’ shape can be done as long as the model can predict experimental results. Since the intrinsic non-convex geometry property of real grains seems to play a major role on the response of the granular medium, it is thus possible to keep this geometrical feature by using cluster of spherical discrete elements, which has the advantage to reduce dramatically the computation cost. Since the porosities found experimentally could not always be obtained with the numerical model—owing to the huge difference in shape, the notion of relative density, which requires a search for minimum and maximum porosities for the model, was chosen to compare the experimental and numerical results. Comparing the numerical simulations with the experimental triaxial tests conducted with relative densities and different confining pressures shows that the model is able to predict the experimental results.

Influence of relative density on granular materials behavior: DEM simulations of triaxial tests

Simulation of railway ballast using crushable polyhedral particles

Enhancement of the structural efficiency and performance of concrete pipes through fiber reinforcement

As a consequence of unequal loading or variable soil conditions, longitudinal bending of buried gravity pipes leads to circumferential pipe cracking or joint opening, which results in groundwater infiltration or leakage. Since joints considerably affect longitudinal pipe behavior, an advanced investigation of this aspect requires knowledge of the joint mechanical properties and particularly of its stiffness. An experimental apparatus has been developed in order to determine the joint behavior under various loading conditions. Results of compression, shear, and bending tests are given in terms of force-displacement plots. A simple rheological bilinear model of the joint is elaborated from compression and shear tests and then validated on the experimental bending results. In general a good agreement is found between model and experimental output. This simple model will be implemented in numerical simulations of buried pipe behavior.

Full-Scale Experimental Determination of Concrete Pipe Joint Behavior and Its Modeling

Statistical homogenization for assemblies of elliptical grains: effect of the aspect ratio and particle orientation

/pdf/movements-induced-by-tunneling-with-an-epb-machine-in-over-4x0p6k81e5.pdf

Fabrice Emeriault

Papers

Full-Scale Experimental Determination of Concrete Pipe Joint Behavior and Its Modeling

Statistical homogenization for assemblies of elliptical grains: effect of the aspect ratio and particle orientation

Movements Induced by Tunneling With an Epb Machine in over Consolidated Soils: Compans Monitoring Section of Toulouse Subway Line B