Mechanical Behavior of Coal-Rock Composite Systems

Coal-rock composite systems, prevalent in deep mining and underground engineering, exhibit complex interactions between soft coal seams and stiffer rock layers. Their mechanical behaviour under load involves multiple failure stages, including initial elastic deformation, progressive microcracking and ultimate brittle or ductile collapse. Key factors influencing this response are loading rate, confining pressure, structural inhomogeneity and stress path. Energy storage and release during deformation govern phenomena such as rockburst and acoustic emission. Understanding composite mechanics is essential for safe mine design, roof support strategies and mitigation of dynamic geological hazards worldwide.

Research from Nature Portfolio

Recent studies have explored the burst tendency of composite rock-coal-bolt systems under varied stress states. Laboratory tests combining thermal imaging with uniaxial and triaxial loading reveal that inclined interfaces amplify energy accumulation and drive multiple stress-strain peaks. A stiffness coefficient and burst energy index have been formulated to predict dynamic failure under deep-seam conditions, highlighting angles around 15° as most critical for sudden collapse.

Further investigation into brittle failure mechanisms of coal-rock composites employed high-speed imaging and numerical simulation to capture sliding-induced tensile fractures. Results show differential lateral deformation leads to stable crack propagation in rock followed by violent coal fragmentation, driven by rapid strain energy release. These findings clarify how energy feedback between materials governs seismic hazard at mining scales.

Mechanical Behavior of Coal-Rock Composite Systems publication trend

The graph below shows the total number of articles in mechanical behavior of coal-rock composite systems across all publications each year (not limited to Nature Index journals).

Technical terms

Uniaxial compression: Loading of a specimen along a single axis until failure, used to characterise basic strength and deformation.

Triaxial compression: Testing under controlled axial stress and lateral confining pressure to simulate in situ stress conditions.

Confining pressure: Lateral stress applied to a sample in triaxial tests, influencing ductility and energy absorption.

Elastic modulus: Ratio of stress to elastic (recoverable) strain, indicating stiffness of coal, rock or composites.

Acoustic emission (AE): High-frequency stress waves released by rapid crack growth, used to monitor damage evolution.

Rockburst: Sudden, violent failure of rock or composite that can release stored elastic energy and pose major safety risks.

References

1. Experimental investigation on rockburst behavior of the rock-coal-bolt specimen under different stress conditions. Scientific Reports (2020).
2. Experimental and numerical investigations on the failure processes and mechanisms of composite coal–rock specimens. Scientific Reports (2020).
3. The Effect of High Loading Rate on the Behaviour and Mechanical Properties of Coal‐Rock Combined Body. Shock and Vibration (2018).
4. Study on Failure Modes and Energy Evolution of Coal‐Rock Combination under Cyclic Loading. Shock and Vibration (2020).
5. Experimental and numerical study of coal-rock bimaterial composite bodies under triaxial compression. International Journal of Coal Science & Technology (2021).