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Cracking Behavior and Failure Characteristics of Rock–Coal–Rock Composites with Varying Thickness
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DOI：10.1007/s00603-026-05688-5.png)
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Abstract
En 中文
This study addresses common issues in coal mining, such as uneven deformation in coal-rock composite roadways, by investigating the mechanical behavior and failure mechanisms of rock-coal-rock composite samples with varying coal thickness ratios under uniaxial compression. The primary aim is to enhance the understanding of these behaviors to improve the safety in thin coal seam mining. Eight groups of specimens were prepared with different coal-to-rock thickness ratios. Acoustic emission event locations correlate well with the evolution of digital image correlation strain fields, both concentrating near the coal-rock interfaces. Computed tomography scans provided three-dimensional visualizations of internal fractures. The results show that greater coal-layer thickness reduces the composite’s peak strength and stiffness but enhances its deformability before failure. DIC data reveal that lateral deformation in the coal layer is smaller near the interface than at the specimen center, while the opposite holds for the rock layers. At the same time, the increase in coal thickness also led to an increase in the lateral deformation of the assembly, with the maximum deformation increasing from 4.48 mm to 6.27 mm. Fractures typically initiate in the coal layer and propagate into the rock layers. In specimens with thinner coal, cracks align nearly parallel to the loading axis, whereas those with thicker coal show greater deviation. Finally, a discussion is proposed to explain interface and thickness effects offering new insights into the mechanical behavior of thin coal seam roadways.
Keywords:
Rock-coal-rock composites
Interface and thickness-ratio effects
Monitoring
Crack propagation
Failure mode
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