The shear behavior of infilled rock joints remains challenging to predict due to complex interactions between joint roughness coefficient (JRC) and infilling ratio. This study examines how joint roughness (JRC 2.8–16.76), infilling ratios (0–2), and normal stresses (0.5–8 MPa) affect shear behavior. Specimens were sheared at 0.6 mm/min while monitoring acoustic emissions to track strength changes and failure patterns under four normal stress levels. Results demonstrate that increasing infilling ratio significantly reduces peak shear strength, residual strength, dilatancy, and shear modulus, with the weakening effect intensified by higher roughness. While roughness enhances shear resistance, its mechanical contribution is counteracted by elevated infilling ratios. A novel tripartite framework reveals the synergistic interplay of three components governing shear strength: roughness-dependent asperity degradation, infill material strength, and rock-fill interface bonding. The dominance of these components shifts dynamically with infilling ratio—roughness effects diminish as infilling dominates, whereas infill and interface contributions rise but are constrained by asperity interactions. Normal stress further modulates this balance by promoting infill compaction while suppressing interface effects. AE analysis corroborates the transition from asperity-driven to infill-controlled failure, marked by reduced shear-induced energy release and altered crack mode dominance. These findings establish a mechanistic basis for evaluating shear behavior in rock masses with heterogeneous infilling, offering theoretical insights for stability assessment and reinforcement design under complex geological conditions.

中文翻译：

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竞争性粗糙度-填充相互作用导致岩石节理中的剪切退化：破坏过渡框架

由于节理粗糙度系数 （JRC） 和填充率之间的复杂相互作用，填充岩石节理的剪切行为仍然难以预测。本研究研究了节理粗糙度 （JRC 2.8-16.76）、填充率 （0-2） 和法向应力 （0.5-8 MPa） 如何影响剪切行为。以 0.6 mm/min 的速度剪切试样，同时监测声发射，以跟踪四个正常应力水平下的强度变化和失效模式。结果表明，提高填充率显著降低了峰值剪切强度、残余强度、剪胀性和剪切模量，较高的粗糙度加剧了这种减弱效应。虽然粗糙度增强了抗剪切性，但其机械贡献被较高的填充率所抵消。一种新的三方框架揭示了控制剪切强度的三个组成部分的协同相互作用：粗糙度依赖性的凹凸度退化、填充材料强度和岩石-填充界面粘合。这些组件的优势随填充率动态变化——粗糙度效应随着填充占主导地位而减弱，而填充和界面贡献增加，但受到凹凸相互作用的限制。法向应力通过促进填充压实同时抑制界面效应来进一步调节这种平衡。声发射分析证实了从凹凸驱动到填充控制失效的转变，其特点是剪切诱导能量释放减少和裂缝模式主导地位改变。这些发现为评价非均质充填岩体的剪切行为奠定了机理基础，为复杂地质条件下的稳定性评估和加固设计提供了理论依据。