Determination of Micro-parameters in DEM Through the Whole Surface Deformation Measurement in the Tri-axial Test

Abstract

The discrete element method (DEM) is becoming increasingly popular for modeling the granular material. The determination of particle micro-parameters is an essential prerequisite for DEM simulations. Laboratory tri-axial compression test has often been used to calibrate particle micro-parameters for DEM simulations. However, the effect of end restraint in the conventional tri-axial test will bring about difficulty in calibrating the parameters accurately. To this end, a new computer-aided measurement method for tri-axial test, so called the whole surface deformation measurement (WSDM), is used to facilitate the parameter determination for DEM simulations. This method allows one to obtain the stress-strain and volumetric strain-strain responses of the central part of the specimen where the strain is proved to be uniform. The inter-particle sliding and rolling friction have been found to exhibit a cross effect on the macro responses of the specimen. This will cause much confusion in the calibration of the sliding and rolling friction coefficient. So a method based on contour graphs is proposed to determine the reasonable combination of the sliding and rolling friction coefficient. Keywords: DEM, micro-parameters, calibration, whole surface deformation measurement, cross effect