Ratcheting of granular materials

TL;DR

This study models the cyclic loading response of granular soils, revealing a ratchet-like grain contact behavior that causes permanent deformation without elastic recovery, highlighting friction's role in soil mechanics.

Contribution

It introduces a discrete polygonal model to analyze cyclic soil response, uncovering ratchet-like contact behavior and the absence of elastic regimes in granular materials.

Findings

Plastic deformation accumulates linearly with cycles

Grain contacts exhibit quasi-periodic ratchet behavior

Friction influences permanent deformation

Abstract

We investigate the quasi-static mechanical response of soils under cyclic loading using a discrete model of randomly generated convex polygons. This response exhibits a sequence of regimes, each one characterized by a linear accumulation of plastic deformation with the number of cycles. At the grain level, a quasi-periodic ratchet-like behavior is observed at the contacts, which excludes the existence of an elastic regime. The study of this slow dynamics allows to explore the role of friction in the permanent deformation of unbound granular materials supporting railroads and streets.