有砟轨道是国内外高速铁路的主要轨道形式之一，由级配碎石组成的道砟层在高速列车荷载下会产生比普通铁路更明显的道砟颗粒运动，易于引发过大的道床沉降，对列车安全运行产生不利影响。但由于缺乏有效测量手段和分析方法，道砟颗粒的运动行为研究仍不多见。本研究基于数码相机和图形识别方法，在全比尺模型试验中开发了道砟颗粒运动追踪技术，将1274 个道床层表层道砟染色并设定为追踪目标；在试验中以垂直向下的角度陆续拍摄道砟层照片，通过追踪目标显示的像素变化特征，对表层道砟颗粒运动进行追踪，定量地分析了不同列车速度和轴重工况下道砟颗粒的运动行为。试验结果表明：表层道砟颗粒运动在低速列车荷载作用下较微弱且主要集中于轨枕附近，但当列车时速提升至360 km时，道砟运动明显加剧并扩展至整个道床层；此外，经统计发现道砟颗粒位移和旋转的发展规律类似；轨道振动会诱发道砟颗粒运动，竖向加速度和水平加速度分别是轨道中心和轨道边缘附近道砟颗粒运动产生的主要原因。道砟颗粒运动和轨道沉降在长期加载中的发展趋势相似，两者同时达到稳定状态；轨道服役性能（如振动特性、累积沉降与轨枕支承刚度）在高速列车荷载的长期作用下会部分劣化，其与道砟颗粒流动的方向和分布密切相关。

As a core infrastructure of high-speed railways, ballast layers constituted by graded crushed stones feature noteworthy particle movement compared with normal railways, which may cause excessive settlement and have detrimental effects on train operation. However, the movement behavior remains ambiguous due to a lack of effective measurement approaches and analytical methods. In this study, an image-aided technique was developed in a full-scale model test using digital cameras and a color-based identification approach. A total of 1274 surface ballast particles were manually dyed by discernible colors to serve as tracers in the test. The movements of the surface ballast particles were tracked using the varied pixels displaying tracers in the photos that were intermittently taken during the test in the perpendicular direction. The movement behavior of ballast particles under different combinations of train speeds and axle loads was quantitatively evaluated. The obtained results indicated that the surface ballast particle movements were slight, mainly concentrated near sleepers under low-speed train loads and greatly amplified and extended to the whole surface when the train speed reached 360 km·h⁻¹. Additionally, the development of ballast particle displacement statistically resembled its rotation. Track vibration contributed to the movements of ballast particles, which specifically were driven by vertical acceleration near the track center and horizontal acceleration at the track edge. Furthermore, the development trends of ballast particle movements and track settlement under long-term train loading were similar, and both stabilized at nearly the same time. The track performance, including the vibration characteristics, accumulated settlement, and sleeper support stiffness, was determined to be closely related to the direction and distribution of ballast particle flow, which partly deteriorated under high-speed train loads.