Nonlinear and Nonequilibrium Dynamics in Geomaterials

TL;DR

This paper investigates the transition from linear to nonlinear elastic behavior in rocks and sandstones, revealing how materials behave under increasing strain and the effects of nonequilibrium states.

Contribution

It provides experimental data and a simple macroscopic model describing the nonlinear transition in geomaterials under strain.

Findings

Linear behavior below a specific strain threshold

Nonlinear behavior accurately modeled by a macroscopic dynamical model

High strain effects involve driven nonequilibrium states

Abstract

The transition from linear to nonlinear dynamical elasticity in rocks is of considerable interest in seismic wave propagation as well as in understanding the basic dynamical processes in consolidated granular materials. We have carried out a careful experimental investigation of this transition for Berea and Fontainebleau sandstones. Below a well-characterized strain, the materials behave linearly, transitioning beyond that point to a nonlinear behavior which can be accurately captured by a simple macroscopic dynamical model. At even higher strains, effects due to a driven nonequilibrium state, and relaxation from it, complicate the characterization of the nonlinear behavior.