Quantifying deviation of elasticity in the quasi-elastic domain of granular soils

Abstract

The absence of purely elastic properties in granular soil is attributed to the reversible sliding that occurs between particles during the loading–unloading cycle, leading to the dissipation of energy through friction. Instead of the strictly elastic domain, we opt for a quasi-elastic domain to examine elastic behavior within the confines of elastic theory. Within this quasi-elastic realm, the response deviates to some extent from the idealized pure elastic behavior posited by the elastic theory. As a result, the elastic constitutive relations applied to granular materials are no longer strictly accurate and may exhibit deviations. With the aim of exploring the deviation of the elasticity of granular materials from idealized pure elasticity, this paper proposes a quantitative approach to assess deviation of elasticity. Specific metrics are formulated to gauge the proximity to pure elasticity. Cyclic triaxial numerical simulation tests, utilizing the discrete element method and accounting for both spherical and non-spherical particles, are conducted to examine the progression of sliding friction energy dissipation and sliding contacts under shear stress within the quasi-elastic domain. The findings indicate that, both at the micro and macroscales, the evolution of quasi-elasticity can be consistently quantified. The threshold for intrinsic slip rate or energy dissipation rate, which corresponds to the termination of initial elasticity, can serve as a quantifiable measure for determining the effective applicability of elastic theory in soil mechanics.