Revisiting the GJK and shape erosion method for contact resolution in DEM

Abstract

This work revisits the Gilbert–Johnson–Keerthi (GJK) and the radial direction-based shape erosion method for the contact resolution of non-spherical particles in discrete element method (DEM). Tests on single contact indicate that the shape erosion would frequently lead to an overestimation on contact overlap, but has a minor effect on contact normal and contact point. The undesired effect of shape erosion on contact overlap is more pronounced for small overlaps and elongated particles. Further study based on random packing and triaxial compression tests suggests that the shape erosion has a dominant effect on the weak contacts within the packing. The overestimation of contact overlaps due to shape erosion may tend to push particles away, thereby dismiss the weak contacts and result in an overall smaller coordination number. Nonetheless, as the contribution of weak contacts to particle shear resistance is relatively small, the shape erosion exhibits negligible effects on the packing fabric and the stress–strain behaviors. In practice, it is suggested that the erosion ratio should be carefully set such that it is compatible (e.g., in a similar order of magnitude) to the overlaps of strong contacts.