水位抬升对高铁路基动力响应与长期沉降的影响

基于Biot理论，建立了轨道-路基-多层饱和土地基耦合系统的2.5维有限元分析模型，提出了考虑实际列车循环荷载作用的路基累积沉降计算方法，分析了水位抬升、列车速度和列车轴重对路基动力响应与长期沉降的影响。研究结果表明：水位抬升对土体振动强度的放大作用并不是局限在水位变化的深度范围内，而是会导致整个路基和地基断面的振动增大，并且这种全断面式的振动放大效应随着列车速度的提高而增强；水位抬升至路基内部时，路基内部会出现显著的超静孔压，最大值达到27.52 kPa，导致有效应力大幅下降，路基内土单元的应力路径向破坏线靠近；当水位仅在地基内抬升时，路基在列车循环荷载作用下的累积变形较小，线路沉降主要来自于地基，当水位抬升至路基内部时，路基累积变形随加载次数的增加发展迅速，100万次加载后变形为19.54 mm，远超容许值，说明路基防水对于线路的长期累积沉降控制具有关键作用；路基和地基的累积变形受列车速度和列车轴重的影响，随着列车轴重的增加而显著增大，并且轴重的增加对路基累积变形的影响相较于地基更强烈，在设计时需要格外关注。

Influences of water level rise on dynamic responses and long-term settlement of high-speed railway subgrade

Based on the Biot theory, a 2.5-dimensional finite element analysis model of the track-subgrade-multilayered saturated soil foundation coupling system was established, and a calculation method for the cumulative settlement of the subgrade considering the actual train cyclic load was proposed. The influences of water level rise, train speed, and axle load on subgrade dynamic response and long-term settlement were discussed. Research results show that the amplification effect of water level rise on the soil vibration intensity is not limited to the depth of water level change, but will lead to the increase in the vibration of the entire subgrade and foundation section. This full-section vibration amplification effect increases with train speed. When the water level rises to the inside of the subgrade, significant excess pore pressure will generate inside the subgrade, and the maximum value can reach 27.52 kPa, resulting in a large drop in the effective stress. Then, the stress path of the soil element in the subgrade will approach the failure line. When the water level only rises within the foundation, the cumulative deformation of the subgrade under the train cyclic load is small, and the railway settlement mainly comes from the foundation. When the water level rises to the inside of the subgrade, the cumulative deformation of the subgrade develops rapidly with the loading cycles, which is 19.54 mm after one million times of loading and exceeds the allowable value largely, indicating that the subgrade waterproofing plays a key role in the long-term cumulative settlement control of the railway line. The train speed and axle load affect the cumulative deformation of the subgrade and foundation, and the increase significantly with the axle load of the train. The increase in the axle load has a stronger influence on the cumulative deformation of the subgrade than the foundation. Thus, the effect of axle load on the cumulative deformation should be well considered in the design.