Interface damage mechanisms and homogeneity-dependent effects in layered composite coal-rock: A new perspective for mining-induced roof disaster prevention

Abstract

Stress represents a critical determinant of dynamic hazards in underground coal mining operations. Heterogeneous geological features substantially influence stress distribution and magnitude throughout mining environments. To investigate the mechanical evolution and failure mechanisms of heterogeneous stratified composite coal-rock (CCR) under mining-induced stresses, three-point bending tests (TPBT) and numerical simulations are conducted on CCR specimens with varying homogeneity indices. Results show a significant positive correlation between CCR fracture strength and the homogeneity index (φ). Higher φ values are associated with more uniform displacement discontinuity zones during the fracturing process. Initial loading is observed to induce compressive strain at the upper coal-rock interface (UI), while tensile strain predominated at both the lower interface (LI) and boundary (LB). Interface strain magnitudes followed the pattern LB>LI>UI, with stability inversely proportional to strain intensity. As φ increases, interfacial stability is reduced, damage severity is amplified, and the critical strain energy release rate is elevated. These variations are primarily governed by the homogeneity-dependent redistribution of particle zones and the downward migration of resistant interfaces. These findings enhance our understanding of fracture propagation in heterogeneous CCR under mining stresses, thereby contributing to improved hazard forecasting and control strategies in coal mine composite roof systems.

Keywords

interface damage mechanisms / roof disaster / layered composite coal-rock / three-point bend tests / homogeneity

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