Acoustic Emission Monitoring in Geological Materials

Acoustic emission (AE) monitoring identifies and records transient elastic waves generated by rapid stress redistributions in geological materials. These microseismic signals arise from phenomena such as crack initiation, frictional sliding along grain boundaries or faults, and phase transformations under varying stress regimes. Modern AE systems employ piezoelectric sensors with bandwidths spanning kilohertz to megahertz, enabling detection of source dimensions from millimetre-scale microfractures to metre-scale rupture processes. In laboratory settings, controlled uniaxial or cyclic loading experiments reveal four characteristic AE stages—quiet, transition, active and decay—corresponding to compaction, elastic deformation, crack propagation and post-peak failure. In the field, dense sensor arrays deployed in mines, tunnels and boreholes allow real-time mapping of event locations and magnitudes, providing insight into evolving stress fields, fault activity and geotechnical stability. AE monitoring has global significance for assessing rock-mass integrity in underground repositories, forecasting slope instabilities in mountainous terrain and evaluating induced seismicity during hydraulic fracturing or CO₂ sequestration. Integration of AE data with complementary techniques—such as microseismic tomography, borehole extensometry and numerical modelling—enhances predictive capabilities and informs risk-mitigation strategies in civil, mining and energy sectors.

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Acoustic Emission Monitoring in Geological Materials publication trend

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Technical terms

Acoustic emission (AE): Elastic waves generated by rapid stress changes within a solid, used to detect and characterise microfractures and other deformation events.

Kaiser effect: The phenomenon by which a material emits no significant AE until a previously applied maximum stress is exceeded, reflecting the rock’s stress ‘memory’.

Felicity ratio: The ratio of stress at first AE onset during reloading to the previous maximum stress, indicating cumulative damage.

In situ stress measurement: Techniques for determining the magnitudes and orientations of stresses within rock masses at depth, often inferred from AE-based memory effects.

References

1. Review on In Situ Acoustic Emission Monitoring in the Context of Structural Health Monitoring in Mines. Applied Sciences (2018).
2. Acoustic Emission Characteristics and Energy Evolution of Red Sandstone Samples under Cyclic Loading and Unloading. Shock and Vibration (2021).
3. Assessment of Appropriate Experimental Parameters for Studying the Kaiser Effect of Rock. Applied Sciences (2020).
4. Mechanical Properties of Metasandstone under Uniaxial Graded Cyclic Loading and Unloading. Applied Sciences (2022).