Predicting failure: acoustic emission of berlinite under compression

Area of Science:

• Materials Science
• Geophysics
• Solid Mechanics

Background:

• Porous materials like berlinite (AlPO4) are susceptible to stress-induced collapse.
• Understanding the mechanics of collapse is crucial for safety in mining and geological applications.

Purpose of the Study:

• To analyze acoustic emission (AE) signals during the stress-induced collapse of porous berlinite.
• To investigate the statistical characteristics of AE events and their relation to porosity and failure mechanisms.

Main Methods:

• Measurement of acoustic emission during stress-induced collapse of berlinite with varying porosity (up to 50%).
• Statistical analysis of AE avalanche energies, fitting to power-law distributions.
• Comparison of collapse behavior in highly porous versus less porous samples.

Main Results:

• AE avalanche energies follow a power law (p(E)dE = E(-ε)dE, ε ~ 1.8).
• Highly porous berlinite (40-50%) exhibits increased AE energy near failure.
• Less porous samples show a reduced energy exponent (~1.4) near failure, indicating critical behavior and a lack of reliable precursors.

Conclusions:

• The study identifies different collapse mechanisms based on material porosity.
• Highly porous materials may exhibit a critical avalanche regime, rendering precursor events unreliable for predicting imminent collapse.
• Pico-seismicity detection of foreshocks is only applicable to highly porous materials for mine collapse warnings.