Research on the Stability of Arc-Fractured Rock–Concrete Composites: Mechanical Response and Energy Evolution

Abstract To mitigate the violent movement of overlying strata in goaf areas, rock–concrete composite support systems are widely utilized. However, the mechanical behavior of such systems under the influence of complex pre-existing defects, such as arc-shaped fractures, remains insufficiently understood. This study aims to clarify the failure mechanisms and the evolution of stability in these composites by evaluating the influence of fracture inclination angles. A synergistic methodology was adopted, combining laboratory uniaxial compression tests with discrete-element method simulations. Based on energy dissipation theory and the strain equivalence hypothesis, a statistical damage constitutive model was established to bridge the gap between microscopic damage and macroscopic mechanical response. The results demonstrate that fracture inclination significantly dictates the energy partitioning and crack propagation patterns within the composite. The established constitutive model, validated by numerical results ( R 2 > 0.999), effectively quantifies how increasing inclination angles enhance energy absorption efficiency and retard structural damage progression. Due to the high toughness of the concrete component, the composite maintains substantial residual bearing capacity, preventing instantaneous failure. These findings provide a robust theoretical framework and practical guidance for optimizing support designs in deep underground excavations with intricate geological defects.