由大粒径堆石和自密实混凝土(SCC)构成的堆石混凝土(RFC),其抗拉性能不仅决定了坝体的变形程度,同时也影响了坝体的耐久性。开展边长600 mm的RFC劈裂抗拉试验,并采用多视角三维重建技术构建基于真实堆石形态的三维RFC离散元模型,分析不同应力水平下RFC劈拉破坏细观结构演化规律。结果表明:RFC劈裂抗拉强度为2.06 MPa,存在SCC劈裂、堆石劈裂、堆石剥落3类破坏形态;劈拉破坏过程中不同应力水平下裂纹数量逐步增多,其中,σ_100%时界面过渡区(ITZ)裂纹占比达59%(2 408条),为破坏主导裂纹,并且全程破坏为拉伸破坏,拉伸裂纹占比达69%(2 816条);力链呈“局部集中—三维扩展—堆石承载”分阶段演化特征,σ_100%时呈椭圆形贯通分布,堆石成为主要承载体;颗粒呈上下端向中部移动并伴随左右偏转的移动轨迹,σ_70%时出现分层现象。研究明确了真实堆石形态下RFC劈拉破坏的细观特征与定量演化机制,可为RFC工程抗拉性能数值模拟提供理论参考。

[Objective] Rock-filled concrete (RFC), formed by large-size rockfill and self-compacting concrete (SCC), possesses tensile properties that not only determine the deformation of dam structures but also affect their durability. Laboratory test studies on large-scale RFC specimens have yielded relatively limited splitting tensile test data; meanwhile, numerical models predominantly adopt randomly generated rockfill configurations, and studies on the mesoscopic failure mechanisms of large-scale RFC based on realistic rockfill morphologies remain scarce. This study aims to address this gap. [Methods] Splitting tensile tests were performed on RFC specimens with a side length of 600 mm. A three-dimensional discrete element model of RFC with realistic rockfill geometries was established using multi-view 3D reconstruction technology. The mesostructural evolution of RFC during splitting tensile failure at various stress levels was analyzed. [Results] The splitting tensile strength of RFC is 2.06 MPa, and three failure modes are identified, namely SCC splitting, rockfill splitting, and rockfill spalling. The number of cracks increases progressively with rising stress levels during the failure process. At σ_100%, cracks in the interfacial transition zone (ITZ) account for 59% (2408 cracks) of the total cracks and act as the dominant failure cracks. While tensile cracks dominate the entire failure process, reaching 69% (2 816 cracks) at σ_100%. The evolution of force chains presents a staged distribution characteristic from local concentration to three-dimensional expansion, and then to rockfill bearing, and present an elliptical through-distribution at σ_100%, with rockfill becoming the primary load-bearing component. Particles move from the upper and lower ends toward the middle with lateral deflection, and stratification occurs at σ_70%. [Conclusion] This research reveals the mesoscopic characteristics and quantitative evolution mechanism of splitting tensile failure in RFC with realistic rockfill morphologies, and provides a theoretical reference for numerical simulations of the tensile performance in RFC engineering.