Predicting Failure: Acoustic Emission of Berlinite under Compression

TL;DR

This study analyzes acoustic emission signals during the stress-induced failure of porous berlinite, revealing different collapse mechanisms and a potential early warning method for mine collapse detection in highly porous materials.

Contribution

It provides new insights into AE avalanche behavior in porous berlinite and proposes a method for early failure warning based on pico-seismicity detection.

Findings

AE avalanche energies follow a power law distribution.

Highly porous berlinite shows increased energy emission near failure.

Less porous samples exhibit critical behavior with precursor events.

Abstract

Acoustic emission has been measured and statistical characteristics have been analyzed during the stress-induced collapse of porous berlinite, AlPO4, containing up to 50 vol% porosity. Stress collapse occurs in a series of individual events (avalanches), and each avalanche leads to a jerk in sample compression with corresponding acoustic emission (AE) signals. The distribution of AE avalanche energies can be approximately described by a power law over a large stress interval. We observed several collapse mechanisms whereby less porous minerals show the superposition of independent jerks, which were not related to the major collapse at the failure stress. In highly porous berlinite (40% and 50%) an increase of the energy emission occurred near the failure point. In contrast, the less porous samples did not show such an increase in energy emission. Instead, in the near vicinity of the main failure point they showed a reduction in the energy exponent to ~ 1.4, which is consistent with the value reported for compressed porous systems displaying critical behavior. This indicated that a critical avalanche regime with a lack of precursor events occurs. In this case, all preceding large events were false alarms and unrelated to the main failure event. Our results identify a method to use pico-seismicity detection of foreshocks to warn of mine collapse before the main failure collapse occurs, which can be applied for highly porous materials only.