Rupture by damage accumulation in rocks

TL;DR

This paper reviews damage accumulation in rocks, linking microcrack development to macro-scale failure, and introduces a numerical model that simulates observed damage patterns across scales.

Contribution

It provides a comprehensive review of damage processes in rocks and presents a numerical model that captures complex damage patterns observed from laboratory to geological scales.

Findings

Damage exhibits fractal spatial properties.

Damage clustering increases near failure.

Power-law energy distributions characterize acoustic emissions.

Abstract

The deformation of rocks is associated with microcracks nucleation and propagation, i.e. damage. The accumulation of damage and its spatial localization lead to the creation of a macroscale discontinuity, so-called "fault" in geological terms, and to the failure of the material, i.e. a dramatic decrease of the mechanical properties as strength and modulus. The damage process can be studied both statically by direct observation of thin sections and dynamically by recording acoustic waves emitted by crack propagation (acoustic emission). Here we first review such observations concerning geological objects over scales ranging from the laboratory sample scale (dm) to seismically active faults (km), including cliffs and rock masses (Dm, hm). These observations reveal complex patterns in both space (fractal properties of damage structures as roughness and gouge), time (clustering, particular trends when the failure approaches) and energy domains (power-law distributions of energy release bursts). We use a numerical model based on progressive damage within an elastic interaction framework which allows us to simulate these observations. This study shows that the failure in rocks can be the result of damage accumulation.