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

拟议项目的目的是尽早和可靠地检测由于铁轨底座/底土中粘性土的塑性变形而引起的局部不稳定。只要能够识别与轮轨力有关的典型的与频率和幅值有关的动态附加刺激作为局部不稳定存在的指标，这可以简单地用于实际应用，以分析轴箱加速度的连续记录，即使是常规列车，以便在早期阶段识别局部不稳定，并将该方法集成到铁路维护管理中。为了实现这一总体目标，应使用由此申请的子项目EPIB 1.2开发的校准的地基-地基相互作用模型，通过数值模拟来评估地基/基础结构中的局部不稳定对轮轨力的影响。从轮轨力的动态分量可以在以后的实践中通过轴箱的加速度来评估轮轨力，可以识别局部失稳的当前形式，以便及早采取适当的措施。因此，作为拟议工作包EPIB 1.2的一部分，应使用动态连续模型来识别存在局部不稳定性的指标，以模拟动应力上部结构、下部结构和地基的典型系统响应。这些问题的岩土工程精确的数值模拟是具有挑战性的，因为在这样的模拟模型中，上部结构、下部结构和地基土中的动力行为和荷载分布以及土层中的波的传播必须真实地表现出来。它的目的是在一个完整的三维模型中模拟整个系统，以便实施基础性研究。描述土体在动态荷载和小应变下的特性对于模拟是至关重要的。物理模拟将采用无粘性土的亚塑性本构模型和粘性土的超塑性本构模型。为了标定模型，将对EPIB 2工作包进行的现场调查(现场测量)进行适当的反分析。由于轮轨力是由与刚度比和车辆侧参数相关的受载轨道的几何形状决定的，因此模型必须表示相应长的轨道区段。

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.