Due to the excellent drainage performance of the ballast, existing studies mainly focus on the dynamic response of ballast under field capacity or saturation. Attention has rarely been paid to dynamic changes in moisture content and potential influences. In this article, we firstly conduct a model test to determine the variation of ballast moisture content under artificial rainfall. After that, a full-scale model test with cyclic loading is carried out to study the effect of moisture content variation on the macro-microscopic response of the ballast bed, where several wireless particle sensors are installed to obtain ballast motion characteristics at strategic locations. The results show that the moisture content increases gradually and stabilizes at a flat peak under rainfall, despite the excellent drainage performance of ballast bed. After halting rainfall, the moisture content drops back to field capacity, which indicates dynamic flowing surface water on ballast particles under rainfall. Such flowing surface water brings changes to the original dynamic equilibrium of ballast bed: macroscopically, the deformation rate of stabilized ballast bed increases significantly, reaching a local peak under field capacity; microscopically, the - and -angular accelerations of the ballast show positive correlation with rainfall intensity. The multiscale responses indicate that field capacity is a critical moisture content.

中文翻译：

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含水率变化引起的道碴床宏观微观动力特性

由于道碴具有优异的排水性能，现有的研究主要集中在现场容量或饱和状态下道碴的动态响应。很少有人关注水分含量的动态变化和潜在影响。在本文中，我们首先进行了模型试验，以确定人工降雨下道碴含水量的变化。之后，进行了循环加载的全尺寸模型试验，研究含水率变化对道碴床宏观微观响应的影响，其中安装了多个无线颗粒传感器以获得关键位置的道碴运动特征。结果表明，尽管道床排水性能良好，但在降雨条件下，含水率逐渐增加并稳定在平峰。降雨停止后，含水量回落至田间持水量，这表明降雨下道碴颗粒上的地表水动态流动。这种流动的地表水使道床原有的动态平衡发生了变化：宏观上，稳定道床的变形率显着增大，在现场能力下达到局部峰值；微观上，道碴的β和β角加速度与降雨强度呈正相关。多尺度响应表明田间持水量是一个关键的含水量。