Predicting compressive–shear fracture in rock masses containing complex flaw distributions remains a major challenge in rock engineering. We propose an improved non-ordinary state-based peridynamics (NOSB-PD) model to simulate rock fracture behavior in this work. A stabilized NOSB-PD formulation is developed by incorporating a bond-level deformation gradient strategy to effectively suppress the zero-energy mode inherent in conventional NOSB-PD formulations, thereby ensuring deformation compatibility and numerical robustness. More importantly, the triple-shear energy criterion is introduced into the PD framework for the first time, enabling a more accurate characterization of shear fracture in rocks under complex stress states. The proposed NOSB-PD model is validated using two examples, demonstrating its excellent capability in suppressing the zero-energy mode and capturing fracture behavior in rock under compressive–shear conditions. Subsequently, the proposed model is used to systematically investigate the influence of flaw distribution on crack propagation and failure modes in rocks. The results indicate that variations in flaw distribution alter the local stress field, leading to a change in the rock fracture mode. Consequently, the rock bridge failure mode transitions from shear-dominated direct coalescence to mixed tensile-shear failure, and finally to tension-dominated indirect failure. The overall rock specimen is more prone to tensile–shear-mixed failure under conditions of shorter rock bridges with larger inclinations, or longer rock bridges with smaller inclinations. These findings provide new insights into the role of flaw distribution on rock fracture behavior.
Rock-filled concrete (RFC) is a three-phase heterogeneous composite composed of large-size rockfill, self-compacting concrete (SCC), and the interfacial transition zone (ITZ) between them. Its mechanical performance is jointly affected by the rockfill skeleton effect and the properties of the ITZ. Existing studies still provide insufficient understanding of how interfacial properties and rockfill characteristics influence the splitting tensile performance and damage evolution mechanism of RFC. In this study, splitting tensile tests of RFC were conducted based on an actual engineering project, and an engineering-scale three-dimensional mesoscopic finite element model was established based on the experimental results. The effects of ITZ strength, rockfill strength, and rockfill particle size on the splitting tensile mechanical response, damage evolution process, and failure morphology of RFC were investigated. The results show that when σITZ ∕ σscc increased from 0.2 to 1.0, the splitting tensile strength of RFC increased by 36.75%; when σRock ∕ σscc increased from 1.0 to 5.0, the splitting tensile strength increased by 39.65%. The splitting tensile strength of RFC increased with increasing ITZ strength and rockfill strength and gradually approached saturation, with threshold values of σITZ ∕ σscc = 0.8 and σRock ∕ σscc = 4.0, respectively. The influence of rockfill particle size on splitting tensile strength showed a trend of first increasing and then decreasing. Compared with a single particle size distribution, a graded particle size distribution improved the rockfill skeleton structure and more effectively enhanced the splitting tensile performance of RFC. Overall, improving ITZ quality and adopting a properly graded rockfill particle size distribution are important approaches for enhancing the splitting tensile performance of RFC, and the findings provide a theoretical basis for RFC material design and engineering applications.