Failure mechanism analysis and tensile constitutive model of basalt fiber concrete-rock interface based on fiber surface modification

This study investigates the tensile failure mechanism at the concrete-rock interface and proposes a concrete-rock interface tensile mechanical constitutive model considering the degree of rock surface indentation and surface morphology. The Brazilian disc splitting test results demonstrate that the depth and width of rock surface indentations collectively characterize the indentation angle θ, thereby influencing the tensile strength of the interface. Specifically, when 0° ≤ θ < 45°, the concrete-rock interface exhibits a tension-shear stress state, where cracks propagate along the interface leading to the debonding of the rock and concrete. When 45° ≤ θ ≤ 90°, the concrete-rock interface adopts a compression-shear state, with cracks gradually transitioning from the interface to the concrete interior. The latter scenario enables the higher tensile performance of the concrete-rock interface compared to interface fracture. Excessive indentation depth compromises the tensile strength of the interface by inducing bending moments. A mechanical model for the tensile behaviour of the concrete-rock interface is proposed, which effectively predicts the tensile strength of the interface and its evolutionary process.