Identification Method of Deformation Localization in DEM-Simulated Granular Geomaterials Based on Contact Deformations

Abstract

Deformation localization of granular geomaterials is critical in analyzing the stability of earth structures. This paper presents a new and simple method for quantitatively identifying deformation localization in the granular geomaterials simulated by the discrete element method (DEM) from a new perspective of the microscale. The method involves a contact-deformation-based indicator, ξ, to describe the deformation field and a corresponding threshold, ξthr, to highlight the localized deformation from the surrounding zone. The indicator ξ is determined by dividing the relative translation of the two contact points in a contact by the sum of the radii of the two contacted particles. On the basis of this determination, the ξ can always be computed whether the two particles stay in contact or subsequently separate (it can be understood as the disturbance degree of an initial contact). The threshold ξthr is quantitatively determined according to the inflection point on the Nξ'/Ntot−ξ curve (where Nξ' is the number of contacts with ξ larger than a specified value ξ', and Ntot is the total initial contact number). The zone of ξ > ξthr was proved as the explicit shear band via a series of biaxial tests on sands. The modeling results indicate that a smaller ξthr corresponds to a more concentrated or narrower localized deformation zone. The proposed method was also extended to search the failure surface of a granular slope and to recognize crack growth and coalescence in a sandstone. The good agreement of the simulated and experimental results suggests the capability of the method in further research of granular system deformation and failure problems.