Detection of local instabilities caused by plastic deformations of cohesive soils in the substructure / subsoil of railway tracks (EPIB1.2)

该项目的目的是尽早可靠地检测由铁路轨道下部结构/地基中粘性土塑性变形引起的局部不稳定性。只要有可能识别关于轮轨力的典型动态附加刺激，其涉及频率和幅度作为局部不稳定性存在的指标，这可以以简单的方式用于实际应用，以分析轴箱加速度的连续记录，即使是常规列车，在早期阶段识别局部不稳定性，并将此方法纳入铁路维修管理中。为实现这一总体目标，应通过数值模拟评估地基/下部结构中局部不稳定性对轮轨力的影响，该数值模拟应使用由地基开发的经校准的地基-地基相互作用模型。项目EPIB 1.2特此申请。从轮轨力的动态分量中，可以在以后的实践中通过轴箱的加速度来评估，可以识别当前形式的局部不稳定性，并可以及早采取适当的措施。因此，作为拟定工作包EPIB 1.2的一部分，应通过使用动态连续体模型来模拟动态应力上部结构、下部结构和地基的典型系统响应，从而确定局部不稳定性的存在指标。在此基础上，评价基础的筛选指标的总体目标，这种局部不稳定性将提供。岩土工程精确的数值模拟这些问题是具有挑战性的，因为在这样的模拟模型中的动力特性和荷载分布在上部结构，在下部结构和在地基土，以及波在土层中的传播必须真实地表示。它的目的是在一个完整的三维模型中模拟整个系统，用于基础研究的实施。在动荷载和小应变条件下的土壤特性的描述是模拟的关键。物理模拟将通过应用亚塑性本构模型和超塑性本构模型来实现，对于非粘性土采用粒间应变，对于粘性土采用超塑性本构模型。为了校准模型，将对工作包EPIB 2进行的适当的现场调查（现场测量）进行反分析。由于动态轮轨力是由与刚度比和车辆侧参数相关的承载轨道的几何形状决定的，因此模型必须代表相应的长轨道截面。

The aim of the proposed project is to detect as early as possible and reliably local instabilities caused by plastic deformations of cohesive soils in the substructure / subsoil of railway tracks. As far as it becomes possible to identify typical dynamic additional stimulations regarding the wheel-rail forces concerning frequency and amplitude as indicators of the presence of local instabilities, this could be used in a simple manner for practical applications to analyze the continuous records of the acceleration of the axle-box, even with regular trains, to identify local instabilities in an early stage and to integrate this method into the railway maintenance management.To achieve this overall objective, the impact of local instabilities in the subsoil / substructure on the wheel-rail forces shall be evaluated by numerical simulations using a calibrated subrade-subsoil interaction model developed by the sub-project EPIB 1.2 applied for hereby. From the dynamic components of the wheel-rail forces, which can be evaluated in the later practice by the acceleration of the axle-box, the current form of a local instability can be identified and appropriate measures can be taken early. As part of the proposed work package EPIB 1.2 therefore indicators for the presence of local instabilities shall be identified by using a dynamic continuum model for the simulation of the typical system response of the dynamically stressed superstructure, substructure and subsoil. Based on this the valuation basis for the overall goal of a screening indicator for such local instabilities will be provided.The geotechnical accurate numerical simulation of these issues is challenging, since in such a simulation model the dynamic behavior and the load distribution in the superstructure, in the substructure and in the subsoil as well as the wave propagation in the soil layers must be represented realistically. It is intended to simulate the overall system in a complete three-dimensional model for the implementation of fundamental studies. The description of soil behavior under dynamic loads and at small strains is crucial for the simulation. The physical modeling will be realized by applying a hypoplastic constitutive model with intergranular strains for non-cohesive soils and a hyperplastic constitutive model for cohesive soils.To calibrate the model appropriate investigations in situ (field measurements) carried out by work package EPIB 2 will be back-analyzed. Since the dynamic wheel-rail forces are determined by the geometry of the loaded track correlated with the stiffness ratios and the vehicle-side parameters, the model must represent a correspondingly long track section.