MODELLING HIGH-SPEED RAILWAY-INDUCED VIBRATIONS AROUND TUNNELS (GROUND-SUPPORT)

科学背景在过去的30年里，人口密集的城市之间对快速通勤的需求有所增加。这一点很明显，高速铁路线主要在中欧，在那里你可以在2小时内旅行500 - 600公里。随着技术的进步和汽车的环境优势以及所遇到的社会效益，对这种基础设施的需求也在增加。后者意味着，由于地形限制，连接（偏远）地区的铁路隧道数量也在增加。铁路隧道特别是高速铁路的一个关键问题是列车通过时产生的振动的传播。尽管在调查和分析高速铁路线的地面振动方面取得了重大的科学进展（Connolly et al. 2013; 2015; 2016），但它通常集中在路堤和土壤上。在隧道环境中，振动从隧道支架传播到围岩或地面，这是科学知识的空白。拟议的项目旨在更好地了解高速铁路引起的振动的启动和传播对隧道行为的影响。更具体地说，这个项目的主要重点是研究振动是如何从支撑系统传播到地面的，以及不同岩石（岩体）和不同类型的地面在受到动态加载时，特别是随着时间的推移，以不同的方式表现出来的系统界面。控制其力学行为的主要因素之一是地质，更具体地说是矿物含量及其结构特征（Paraskevopoulou, 2016, et al. 2017,2018）。在隧道施工过程中，隧道附近的应力会重新分布，从而形成开挖破坏区（EDZ），在该区域内，新的裂缝和裂缝会形成，或者现有的裂缝和裂缝会扩展和扩大，随着时间的推移，这些裂缝和裂缝会导致逐渐的破坏和破坏。波的传播路径（振动）直接受到后者的影响，因为它取决于地质环境和断裂刚度上的不连续面（节理、断层等）、弱点要素（剪切带、地质接触等）。高速铁路引起的振动引起的断裂会进一步恶化和破坏EDZ。能够预测隧道系统在高速铁路运行期间的反应是至关重要的，特别是对系统的寿命和弹性而言。该项目将包括实地工作，在特定的HS2隧道现场收集样本，在3-D物理模型上进行实验测试，以在较小的范围内模拟实际问题，并使用传感器监测系统的反应，以及使用有限元、有限差分、不同元素方法进行数值分析。试验结果将用于数值分析，以建立能够描述隧道结构支撑单元与地面界面响应的本构模型。该项目的最终目标是开发实用的工具和模型，这些工具和模型不仅可以在研究领域中使用，而且在工业中也非常重要。目的和目标主要目的是为了更好地理解高速铁路引起的振动的产生和传播所导致的隧道行为。目标包括：-发展本构关系，以描述高速铁路诱发振动时隧道（地面支撑）系统的力学行为-了解振动诱发机制如何在一定时间尺度上影响力学行为。-评估这些结果对骨折闭合（或不闭合）等问题的长期影响

SCIENTIFIC BACKGROUNDThe demand for fast commuting between densely populated cities has increased over the last 30 years. This is evident with the existence of high-speed railway lines mainly in central Europe where within in 2 hours you can travel 500 - 600 km. The need of such infrastructures has risen along with the technological advancement and the environmental advantage to cars and social benefits that encounters. The latter implies that the number of railway tunnels connecting (remote) areas faster due to topographical limitations has also risen. One of the key considerations on railways tunnels especially high speed lines is the propagation of vibrations generated as the train(s) passes through. Although significant scientific progress has been made on investigating and analyzing on the ground vibrations from high speed rail lines (Connolly et al. 2013; 2015; 2016), it focuses commonly on embankments and soils. There is a gap of scientific knowledge in the tunneling environment where the vibrations propagate from the tunnel support to the surrounding rock or ground. The proposed project aims to develop a better understanding of the tunnel behaviour due to the initiation and propagation of vibrations induced in high speed railways. More specifically the main focus of this project is to investigate how the vibrations propagate from the support system to the ground and this system's interface as different rocks (rock masses) and different types of ground behave in different ways when subjected to dynamic loading, especially over time. One of the main factors controlling their mechanical behaviour is geology and more specifically the mineralogical content and its structural characteristics (Paraskevopoulou, 2016, et al. 2017, 2018). During tunnel construction there is re-distribution of stresses around the tunnel vicinity that creates the Excavation Damaged Zone (EDZ) in which new cracks and fractures are formed and or existing cracks and fractures propagate and dilate which can lead to progressive damage and failure over time. The wave propagation path (of vibrations) is directly influenced by the latter, as it depends on the discontinuities (joints, faults etc), elements of weaknesses (shear zones, geological contacts etc) on the geological setting and fracture stiffness (Hildyard, 2007). The EDZ can be deteriorated further and further damaged by fracture initiation due to the high-speed railway induced vibrations. Being able to predict the tunnel system's reaction during high-speed railway operations can be paramount of importance especially for the system's lifetime and therefore its resilience. The project will involve field work for sample collection to specific tunnel HS2 sites, experimental testing on 3-D physical models to simulate in a smaller scale the real problem and monitor the system's response using sensors and as well numerical analyses using finite-element, finite-difference, distinct-element methods. The results of the experimental testing will be used to numerical analyses in order to develop a constitutive model that can describe the response of the interface between the tunnel structural support elements and the ground. The ultimate goal of this project is to develop practical tools and models that can find use not only in the field of research but also in industry is of utmost importance. AIMS AND OBJECTIVESThe main aim is to develop a better understanding of the tunnel behaviour due to the initiation and propagation of vibrations induced in high speed railways. objectives include:-- Developing constitutive relationships to describe the mechanical behaviour of the tunnel (ground-support) system during high-speed railway induced vibrations- Gaining understanding of how the vibration-induced mechanisms can affect the mechanical behaviour on a range of time-scales.- Assessing the implications of these results for issues such as closure (or non-closure) of fractures, long-term