With the Discrete Element method it is possible to model materialsthat consists of individual particles where a particle may rollor slide on other particles. This is interesting because mostof the deformation of granular materials is due to rolling orsliding rather than compression of the grains. This is true evenof the resilient (or reversible) deformations. It is also interestingbecause the Discrete Element method models resilient and plasticdeformations as well as failure in a single process.

The paper describes two types of calculations. One on a smallsample of angular elements subjected to a pulsating (repeated)biaxial loading and another of a larger sample of circular elementssubjected to a plate load. Both cases are two dimensional i.e.plane strain.

The repeated biaxial loading showed a large increase in plasticstrain for the first load pulse at a given load level. Additionalload pulses at the same load level gave decreasing plastic strainrate, in agreement with what is normally observed on granularmaterials. The resilient modulus was much lower than the stiffnessof the elements and was decreasing with increasing deviator stress.At high deviator stresses the stiffness of the assembly of elementswas less than one percent of the stiffness of the elements. Thisis also in good agreement with observations on granular materials.

Plate loading showed a distribution of vertical stress thatwas close to the stress in an elastic continuum. Very little stressconcentration was observed, but this might change if angular elementswere used. The horizontal stresses on the other hand were quitedifferent from the horizontal stresses in an elastic continuum.Modulus and Poisson's ratio calculated at different points ofthe particulate medium, from the stresses and strains, showedlarge variations. Dilation of the material was frequent.