A Discrete Numerical Study Of The Effect Of Loading Conditions On Granular Material Response
It is well-known that all three principal stresses play a role in the stress-strain-strength response of solids and granular materials, yet axisymmetric compression tests and direct shear tests are typically used for the determination of design parameters, even when field conditions may be plane strain (e.g., behind a long retaining wall). The effects of loading conditions on the macroscale response of granular materials have been studied extensively using experimental methods and it is relatively straightforward to quantify the variations in material macroresponse using continuum constitutive equations. However, these methods provide relatively little insight into the driving micromechanics that govern macroscale behavior, particularly in soils that fail in a non-constitutive manner (e.g., via regions of high localized strain). A series of numerical experiments has been performed to assess the effects of loading (i.e., boundary) conditions on particulate material response. Three-dimensional numerical specimens of approximately 15,000 particles each were assembled to similar void ratios and confining stresses and then subjected to plane strain and axisymmetric compression. Simulated material response is generally in good agreement with previously published experimental results. In the future, it may be possible to exploit the discrete nature of the simulations to observe changes in material microstructure under different boundary conditions.
Keywords: Discrete Element Method, Plane Strain, Conventional Triaxial Compression