Anisotropy-based failure criterion for interphase systems

This paper presents a methodology for estimating the shear strength of interphase systems composed of granular materials and planar inclusions having various degrees of roughness. Existing empirical and semiempirical relationships between strength and surface roughness do not appear to be general and are unable to account for surface-particle interactions at the appropriate scales. The proposed method is based on the contact force anisotropy of those particles that touch the inclusion surface. It was developed using two-dimensional discrete element method simulations of interphase systems constructed within a direct interface shear test device. Particles consist of polydisperse and monodisperse spheres of constant median grain diameter. Surface roughness was varied by using profiles with regular and random asperities, and profiles of manufactured surfaces. Results indicate that the magnitude and direction of average contact total force at the interface controls strength. A bilinear relationship, independent of particle to surface friction coefficient, exists between the principal direction of contact total force anisotropy and strength. Results using the proposed criterion are in good agreement with laboratory results using spheres and subrounded sand. © 2007 ASCE.