The ballastless track has been a widely-used track form in high-speed railway (HSR), however, its application is seriously hampered by the railway heave, which is mainly caused by subgrade swelling. In order to identify the mechanism of HSR subgrade swelling and the rules of swelling-induced railway heave response, long-term longitudinal-continuous deformation monitoring and layered deformation monitoring over a heaving-affected site have been carried out. Furthermore, a coarse-grained soil oedometer was applied to explore the correlations between swelling pressure and swelling ratio of the subgrade filler and mudstone foundation to the on-site water content. With the aid of FLAC^3D-PFC^3D coupled numerical simulation, the influence of different swelling ratios for subgrade filler and mudstone foundation on the railway heave response of a double-block ballastless track under was analyzed. According to the field monitoring results, swelling deformation occurred in both the filler layer and subgrade layer of the heave section, and this combined action within the two layers resulted in railway heave displacement. Laboratory tests indicated that the swelling ratios of the subgrade filler and mudstone foundation under in-situ water content reached 0.205% and 3.325%, respectively. The swelling pressure and swelling ratio in the subgrade filler and mudstone foundation both followed a logistic function relationship with the water content. Numerical results showed that the railway heave amount followed Expassoc and Nelder distribution relationships with the swelling ratios of the subgrade filler and mudstone foundation, respectively. The research results could provide some reference value for the study on the swelling potential of expansive soils and the prediction of railway deformation in railway engineering.

无轨道是高速铁路（HSR）中一种广泛使用的轨道形式，但是，它的应用受到铁路起伏的严重阻碍，这主要是由路基膨胀引起的。为了确定高铁路基胀大的机理和胀大引起的铁路沉陷响应的规律，对沉沉场地进行了长期的纵向连续变形监测和分层变形监测。此外，采用了粗粒土壤饱和度计，探讨了膨胀压力和路基填料和泥岩基础膨胀比与现场含水量之间的关系。借助FLAC ^3D - PFC ^3D耦合数值模拟，分析了不同膨胀比对路基填料和泥石基础对双块式无ball轨道下沉轨道响应的影响。根据现场监测结果，隆起段的填料层和路基层均发生膨胀变形，并且这两层内的这种联合作用导致铁路隆起位移。室内试验表明，在原位含水量下，路基填料和泥岩地基的溶胀率分别达到0.205％和3.325％。路基填料和泥岩地基中的溶胀压力和溶胀率均与水含量呈逻辑函数关系。数值结果表明，铁路起伏量遵循Expassoc和Nelder分布关系分别与路基填料和泥岩地基的膨胀率有关。研究结果可为膨胀土的溶胀潜力研究和铁路工程中铁路变形的预测提供参考。