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Experimental Study on the Mechanical Response and Damage Evolution Mechanism of Coal at Multiple Burial Depths Under True Triaxial Compensation Effect
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DOI：10.1007/s00603-026-05767-7.png)
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Abstract
En 中文
During the extraction of deep coal resources, roadway surrounding rock undergoes stress redistribution and re-equilibration during excavation and support. In this study, comparative tests of radial single-face unloading (XH) and radial support compensation after unloading (ZH) under true triaxial conditions were conducted on coal specimens at different burial depths. By combining mechanical responses with acoustic-emission (AE) evolution characteristics, the damage and failure mechanisms of the coal specimens under the two stress paths and their variation with burial depth were revealed. The results show that ZH enhances the bearing capacity and deformation accommodation capacity of unloaded coal specimens, but its strengthening effect decreases nonlinearly with increasing burial depth under a given compensation stress. Under the XH path, the failure mode of the coal specimens gradually changes from shear-dominated to tensile-dominated with increasing burial depth, whereas tensile cracks dominate under the ZH path. Although the failure morphology of the coal specimens remains relatively intact under the ZH path, the degree of internal crack coalescence is higher. The crack initiation stress $${\sigma}_{CI}$$ was determined using the cumulative ringing-count difference method, and the crack propagation process was divided into four stages. Under the two stress paths, the damage coefficient $${K}_{D}$$ exhibits opposite evolutionary trends with increasing burial depth. The brittleness index shows an S-shaped saturating increase with burial depth and remains consistently higher under the ZH path than under the XH path. Based on the experimental results, an excavation compensation equilibrium model for coal at different burial depths was developed, and a coordinated stress–energy regulation strategy was proposed for deep surrounding rock control. The results of this study provide an experimental basis and theoretical support for the safe exploitation of deep coal resources.
Keywords:
Support compensation
Single-face unloading
Different burial depths
True triaxial
Acoustic emission
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