Weak-phase-dominated fracture characteristics and dynamic degradation modeling of coal gangue concrete under cyclic impact

Abstract

To support the safe and efficient utilization of coal gangue (CG) as aggregate in underground support structures, this study systematically investigates the dynamic fracture response and damage evolution of coal gangue concrete (CGC) under single and cyclic impact loading. Experimental results show that increasing the CG replacement ratio reduces dynamic strength and elastic modulus while raising peak strain. Under cyclic impact, the impact resistance life shortens significantly, and damage evolution follows a “weak-phase-dominated” mechanism driven by the low strength of CG aggregates and weak interfacial zones. As the replacement ratio increases, failure transitions toward a crushing-dominated mode governed by aggregate fracture and interfacial slip. Based on these findings, a dynamic strength degradation model coupling the replacement ratio and impact number is established to predict residual load-bearing capacity after cyclic impact. This work provides a theoretical basis for the design and safety assessment of CG concrete structures in dynamically disturbed underground environments.