<p>The arc floor, located at the lower end of the fully mechanized caving face within the inclined coal seam’s staggered layers, causes gangue to slip and accumulate in the goaf as the face moves forward. The accumulated gangue, in combination with the arc floor, forms a new surrounding rock structure. Under in-situ stress, it interacts with the coal seam below, creating a new force system. As the interaction progresses, the coal is compressed, causing natural damage that destabilizes the arc floor. Studying the mechanical behavior and failure mechanisms of the gangue–coal composite (GCC) is essential for assessing structural safety and understanding similar mining conditions. Confined uniaxial compression tests were conducted on GCC specimens to analyze their strength, deformation, acoustic emission (AE) features, and failure processes with different interface heights and slopes. A discrete element model (DEM) was developed using PFC^3D software to simulate the contact force-microcrack evolution and AE characteristics with moment tensor theory. The results show that GCC failure occurs in distinct stages, with AE responses, <i>b</i>-value changes, and microcrack evolution closely matching the loading and failure process. A decrease in the <i>b</i>-value during coal briquette failure is a key precursor to the coal’s failure and instability in the composite. The interface slope influences the loading state of the coal briquette, changing the position of crack initiation and failure mode. These findings offer valuable insights into the mechanical behavior and failure characteristics of GCCs, providing theoretical support for similar mining conditions.</p>