The composite structure consisting of the coal pillar and backfill material is the critical component for the room-and-pillar mining system, the stability of which is mainly relevant to the interface in between. To eliminate the premature instability and potential disasters attributed to the breakage of the weak interface, the innovative strengthening technique incorporating the carbon fiber-reinforced polymer (CFRP) jacket was recently developed and the comprehensive studies including the uni-axial compression tests and the numerical investigation were carried out. In the present study, the digital interface of the coal-backfill composite was initially reconstructed with the 3D laser scanning and then imported into the mesoscopic continuum-discontinuity coupling model via the PFC-FLAC coupling method. Based on the analysis of the deformation characteristics and damage patterns of the coal -backfill composite, the strengthening mechanism of the exterior CFRP jacket was discussed. The results showed that both the load-bearing performance and the stability of the coal-backfill composite interface have been well enhanced mainly attributed to the effective lateral confinement provided by the exterior CFRP jacket. Moreover, the application of the CFRP jacket enhances the energy dissipation capacity of the coal-backfill composite as suggested by laboratory tests. It is also suggested that both the peak strength and elastic modulus of the coal-backfill composite exhibited the initial decrease and then rising as the interface angle increases. As demonstrated by the systematic research, the CFRP strengthening technique is effective in maintaining the stability of the coal-backfill composites for underground mines.
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