Abstract: For gas storage in abandoned coal mine hard-rock tunnels, the bonding performance between concrete lining and surrounding rock is crucial for maintaining the bearing capacity and air-tightness of the containment structure. However, cyclic internal pressure variations can cause degradation of the interfacial bond. To study the fatigue deterioration characteristics of rock-lining interface strength under cyclic high pressure, direct shear tests were conducted on rock-concrete composite specimens with different interface roughnesses after fatigue loading under varying normal stresses. Strength characteristics were analyzed through interface morphology evolution, stress-displacement curves, peak strength and failure patterns. The results show that shear stress-strain curves can be divided into three stages: crack closure stage (plastic-elastic deformation), crack propagation stage (elastic deformation), and brittle fracture stage (failure). Higher interface roughness and normal stress facilitate more complete development of each stage. Concrete embedded in rock grooves and sandstone columns exhibit mutual extrusion and interlocking effects. Horizontal strain and principal strain display distinct zonal dislocation characteristics. Under cyclic loading, particle breakage occurs accompanied by microcrack propagation. Both rock debris and cracks increase with higher upper stress limits. This study demonstrates that the interface strength characteristics are closely related to fatigue degree, interface roughness and internal pressure magnitude. The findings can provide experimental basis for stability analysis of lined caverns in abandoned mines under compressed air energy storage conditions.

Key words: abandoned coal mines, compressed air energy storage, cyclic loading, strength characteristics, rock-concrete composite specimens