Energy dissipation in granular materials in triaxial tests

Abstract

The triaxial test is used in a laboratory to investigate the behaviour of geotechnical materials (e.g. clays and sands). The difficulty in measuring some properties of granular media such as energy changes throughout the test have motivated the current numerical simulations of this test. This paper presents a description of a series of triaxial tests using LIGGGHTS open source Discrete Element Modelling software in a study of how energy is dissipated in granular media. The simulated triaxial tests are being carried out on cube shaped samples with six mesh walls enclosing the particles. Three of the walls (i.e. bottom, left and back walls) are fixed in position while the other three walls are allowed to move. Energy dissipation will be investigated by tracing changes of the energy terms at various time steps and applying the principle of energy conservation. The relationship between confining pressure, particle size distribution, friction coefficient and the voids ratio with energy dissipation will be investigated during the analysis of the results from the simulations. It is hoped that understanding the relationship between grain scale parameters and energy dissipation will help in the formulation of constitutive relationships within, for instance, the hyperplasticity framework. It is envisioned that relating grain scale parameters to constitutive models will allow the formulation of models that are purely based on the micro mechanics of granular media.