土质路基在高速列车的长期循环荷载下不可避免会发生沉降变形，列车运行速度与路基的沉降有着直接的关联性。随着列车运行速度的不断提高，对不均匀沉降变形的控制要求也越来越严格；同时，路基的不均匀沉降也制约着列车运行速度的提升，故有必要研究无砟轨道路基不均匀沉降对列车运行特性和线路冲击的影响。在既有的列车-轨道垂向耦合动力学理论模型基础上进一步考虑了轨道板下方的CA砂浆层和混凝土垫层的共同作用，建立了更符合实际线路特征的车轨耦合分析模型，并通过与现场测试结果的对比验证了该模型的合理性。基于此模型考察了不同路基沉降分布特征、不同列车运行速度条件下车辆和轨道振动特性，从车辆运行安全性和乘客舒适性两方面的指标总结了沉降的控制要求。计算发现短波长的路基沉降易于引起轮轴较大的加速度响应，线路的沉降幅值控制标准主要由安全性指标(轮轴减载率)决定；而在发生大波长的路基沉降时，主要导致车体加速度响应明显增大，路基沉降控制标准主要由列车车体舒适性指标(车体加速度)所决定，并给出具体的控制参数。

Settlement will occur at subgrade of high-speed railroad caused by repeated loadings from train traffic. Train’s operation speed has a direct correlation with the settlement of railroad subgrade. As train’s running speed increases, the criteria for controlling differential settlement of railroad subgrade becomes higher. Meanwhile, the further increase of train velocity is limited by the subgrade’s differential settlement. It is therefore necessary to investigate the influence of subgrade settlement on the vibration of train and track structure. An updated numerical model is developed based on traditional vertical train-track coupling theory, in which the CA mortar and concrete base beneath slab track are both taken into account. The calculated and in-situ tested results are compared to validate the model and the computation program. Using the program, the amplifications of train-track interaction under different conditions of roadbed settlement and train velocities were analysed. It is concluded that while short-range roadbed settlement result in higher axle acceleration, car body vibration does not increase obviously due to the high frequency of vibration. Therefore, amplitude of settlement should be controlled under the safety standard (axle load reduction rate). In the case of long-range roadbed settlement, however, car body vibration increases obviously. Amplitude of settlement should therefore be controlled under the comfort standard (car body acceleration). The specific control parameters are given at the end.