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Experimental and Simulated Study on the Influence of Rock Separation on the Signal Response and Fracture Mechanism of Roof Strata
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DOI：10.1007/s00603-026-05622-9.png)
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Abstract
En 中文
Roof separation fractures constitute a principal causative mechanism underlying coal-rock dynamic disasters, yet their failure mechanics remain insufficiently understood. This study systematically elucidates the fracture behavior of sandstone subjected to various separation configurations through three-point bending tests (TPBT) integrated with discrete element method (DEM) simulations. The experimental framework incorporates a multifaceted monitoring approach, synergistically combining acoustic emission (AE), digital image correlation (DIC), and 3D profilometry to comprehensively characterize the progressive failure process. By systematically varying the precast crack length (b) and upper-to-lower layer thickness ratio (U/L), we quantitatively delineate the influence of separation geometry on strength characteristics, acoustic response patterns, and fracture evolution mechanisms. Experimental findings demonstrate that separation structures substantially attenuate fracture strength by up to 72.7%, with optimal mechanical stability manifested at U/L = 1. An enhanced AE b-value analytical methodology reveals distinct damage evolution stages: the b-value maintains a range between 0.8 and 2.83 throughout stable crack propagation, but exhibits a precipitous decline below 0.5 at peak load, thereby furnishing a reliable precursory indicator for fracture instability. Two dominant failure modalities emerge from our investigation: (1) progressive failure characterized by small-scale separation, adhering to a “bottom initiation-top penetration” evolutionary sequence, and (2) composite failure governed by large-scale separation mechanisms. Three-dimensional profilometry substantiates that fracture surface roughness escalates with increasing b while diminishing with elevated U/L ratios, reflecting distinct energy dissipation mechanisms. A fracture mechanics model predicated on simply supported beam theory establishes the quantitative relationship f ∝ b2/(U/L), where f represents the deflection magnitude of the overlying strata. Six characteristic fracture patterns are systematically identified and correlated with disparate mining-induced dynamic disaster typologies. Collectively, these findings advance fundamental understanding of roof separation fracture mechanics and furnish quantitative criteria for hazard assessment in underground coal mining operations.
Keywords:
Dynamic disasters
Roof separation
Fracture mechanism
Signal response
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