针对大仓面堆石混凝土浇筑过程中自密实混凝土流动隐蔽、难以观测的问题,采用计算流体力学方法,基于Herschel-Bulkley宾汉姆流体模型表征自密实混凝土的流变特性,开展大仓面浇筑过程的数值模拟研究。基于三维堆石体自由堆积模型提取典型二维截面,构建长10.0 m、高1.5 m、堆石率为55.0%的二维不规则真实堆石模型,系统分析了大仓面浇筑过程中自密实混凝土的流动演化过程、自由液面上升规律及水平推进距离的时空演化特征。结果表明:自密实混凝土在堆石骨架内流动呈现不规则锯齿状形态,局部因倒扣结构、流动分离及壁面摩擦等因素形成瞬时空腔;纵向液面抬升在浇筑点附近表现为上下双向推进特征,远离浇筑点区域呈现自下而上的抬升模式,整体抬升具有显著的空间滞后性,上升速度逐渐减缓;水平流动距离随时间呈非线性衰减,前期快速推进,后期受屈服应力与壁面摩擦影响转为缓慢推进。研究成果可为堆石混凝土坝现场填充程度判断与浇筑点控制提供理论依据。

[Objective] To elucidate the inherently concealed flow trajectories and evaluate the structural compactness in large-lift rock-filled concrete (RFC) dam construction, this study systematically quantifies the internal flow evolution, vertical free surface lifting behaviors, and horizontal propagation dynamics of self-compacting concrete (SCC). Specifically, we aim to identify the mesoscopic mechanical mechanisms governing localized void formation within highly irregular rockfill skeletons. The ultimate objective is to provide a robust, quantitative theoretical foundation for optimizing pouring point switching strategies, determining maximum allowable flow distances, and mitigating the risk of structural defects in field engineering applications. [Methods] A high-fidelity numerical framework was developed by coupling Computational Fluid Dynamics (CFD) with the Volume of Fluid (VOF) multiphase model to dynamically track the transient air-concrete interface. To accurately represent the rheological behavior of the mixture, self-compacting mortar (SCM) was treated as an equivalent continuous fluid governed by the Herschel-Bulkley non-Newtonian model, with the rheological index precisely set to m=1 to capture Bingham fluid characteristics. A fundamental methodological approach of this study was the generation of a highly realistic macroscopic rockfill geometric model. Diverging from traditional approximations using simplified spherical particles or regularized porous arrays, an Xtended Position-Based Dynamics (XPBD) rigid-body physics engine was employed. This engine simulated the natural, gravity-driven free-fall and mechanical accumulation of over 2 100 high-resolution, 3D-scanned physical rock blocks. From this large-scale 3D granular assembly, a representative 2D computational domain measuring 10.0 m in length and 1.5 m in height, with a precise 55.0% rockfill volume fraction, was extracted. This specific boundary condition critically bridges the discrepancy between idealized laboratory setups and the highly chaotic topological environments encountered at actual dam construction sites. [Results] Numerical simulations yielded high-resolution spatiotemporal data characterizing the SCC flow through the realistic rockfill skeleton. Regarding mesoscopic flow kinematics, the SCC advancement front demonstrated a highly tortuous, zigzag trajectory induced by continuous geometric blockages and flow bifurcations around massive aggregates. The transient formation of internal cavities was accurately captured, revealing a three-fold micromechanical void-formation paradigm: (1) semi-enclosed "undercut" topologies at the basal surfaces of the rocks mechanically trap upward-escaping air; (2) severe flow separation at acute rock corners induces localized stagnation zones where the local driving pressure is insufficient to overcome the fluid’s yield stress; and (3) continuous surface friction generated by rough aggregate textures dissipates kinetic energy, suppressing fluid advancement along boundary edges. Second, the vertical free-surface lifting behaviors exhibited pronounced spatial heterogeneity. Regions directly beneath the pouring point exhibited bidirectional expansion, whereas distal regions strictly followed a delayed, bottom-up filling mode. A critical inflection point was identified in the mid-range lifting curves, marking a severe degradation in local volumetric filling efficiency following an initial rapid elevation phase. Third, horizontal propagation dynamics demonstrated a distinct nonlinear temporal attenuation. Initially, high kinetic energy drove a rapid, linear horizontal advancement. Subsequently, the accumulation of frictional and rheological resistance shifted the flow into a viscosity-dominated squeezing regime, characterized mathematically by a quadratic, downward-opening decay function. Finally, integrating these flow coordinates into a novel 3D spatiotemporal surface explicitly quantified the severe deceleration effects imposed by the complex porous media over extended distances. [Conclusions] This study represents a significant methodological innovation in computational civil engineering by pioneering the simulation of complex SCC pouring processes utilizing an ultra-realistic, XPBD-generated rockfill topological model. Based on the extracted flow kinematics, it is concluded that localized structural voids are mechanically deterministic phenomena driven primarily by undercut air-trapping, low-shear fluid stagnation, and boundary friction. Furthermore, the identification of spatial hysteresis in vertical lifting and the quadratic deceleration of horizontal propagation quantitatively proves the strict physical limitations inherent to single-point pouring operations. The derived nonlinear decay functions and efficiency inflection points provide field engineers with a rigorous quantitative framework to mathematically formulate optimal pouring point switching intervals and rationally restrict maximum allowable flow distances. Moving forward, it is recommended that engineering practices leverage these predictive thresholds to design dynamically adaptive pouring systems, thereby effectively mitigating internal void defects and ensuring the macroscopic structural integrity and ultimate compactness of rock-filled concrete dams.