This paper presents a practical method for identifying the fundamental design parameters of a multilayered earth structure in ballastless tracks at an operational speed of 400 km/h. The properties of subgrade materials and layer thickness are determined based on vehicle–track coupled dynamic numerical analysis and integrated empirical models incorporating a threshold cyclic strain approach. The principle of the proposed method is to limit train-induced strain and deformation in the foundations in order to achieve satisfactory long-term track performance. Firstly, the critical velocity effect is introduced and briefly assessed for design purposes. Dynamic amplification factor (DAF) is obtained from the statistical analysis of simulated results of vertical vehicle–track coupled dynamic models. A trapezoidal stress pattern is used to characterize the mobilized stress distribution on the subgrade surface under two-axle moving loads of a vehicle on a slab track. The attenuation law of excess vertical soil stress in a substructure under traffic loads is consequently reproduced using Boussinesq’s equation. Next, two threshold strains are defined in accordance with the accumulation rate of residual subgrade settlement, predicted by empirical models as a function of the $K_{30}$ value (modulus of subgrade reaction) and plasticity index of the subgrade aggregate. Following this, the abovementioned results are synthesized into design criteria that can be readily utilized. The application of the proposed method is illustrated by an example of earthwork design. Field observations are finally presented for the validation of the developed approach. The design methodology will improve knowledge of slab track substructure design and is expected to extend the applicability of the current railway code to higher train speed conditions.

本文提出了一种实用方法，用于以400 km / h的运行速度识别无ball轨道中多层土结构的基本设计参数。路基材料的性质和层厚是根据车辆-轨道耦合动态数值分析和结合阈值循环应变方法的综合经验模型确定的。所提出方法的原理是限制地基中列车引起的应变和变形，以获得令人满意的长期轨道性能。首先，引入临界速度效应并对其进行简要评估以达到设计目的。动态放大因子（DAF）是通过对垂直车轨耦合动态模型的模拟结果进行统计分析而获得的。梯形应力模式用于表征在平板轨道上车辆的两轴移动载荷下路基表面上的动应力分布。因此，使用Boussinesq方程可得出交通荷载作用下子结构中垂直竖向土壤应力过大的衰减规律。接下来，根据残余路基沉降的累积速率定义两个阈值应变，通过经验模型预测该阈值应变是该函数的函数。${ķ}_{30}$值（路基反应模量）和路基骨料的可塑性指数。然后，将上述结果综合为易于使用的设计标准。土方工程实例说明了该方法的应用。最后提出现场观察，以验​​证所开发方法的有效性。该设计方法将提高对板式轨道下部结构设计的了解，并有望将当前铁路法规的适用性扩展至更高的列车速度条件。