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

科学背景在过去的30年里，在人口稠密的城市之间快速通勤的需求有所增加。这一点很明显地体现在高速铁路线的存在上，主要是在中欧，在那里在2小时内你可以行驶500-600公里。随着技术的进步和对汽车的环境优势以及所遇到的社会效益，对这类基础设施的需求也在上升。后者意味着，由于地形限制，连接(偏远)地区更快的铁路隧道数量也有所增加。列车(S)通过时产生的振动传播是铁路隧道，特别是高速线路上的关键考虑因素之一。尽管在调查和分析高速铁路线的地面振动方面已经取得了重大的科学进展(Connolly等人)。2013；2015；2016)，它通常集中在堤坝和土壤上。在隧道施工环境中，振动从隧道支架传播到围岩或地面，存在着科学知识的空白。拟议的项目旨在更好地了解由于高速铁路引起的振动的引发和传播而导致的隧道行为。更具体地说，这个项目的主要重点是研究振动如何从支撑系统传播到地面和该系统的界面，因为不同的岩石(岩体)和不同类型的地面在动态荷载作用下表现出不同的方式，特别是随着时间的推移。控制其力学行为的主要因素之一是地质，更具体地说是矿物学含量及其结构特征(Paraskevopoulou，2016，等人)。2017、2018)。在隧道施工过程中，隧道周围的应力重新分布，形成开挖损伤区(EDZ)，在EDZ中形成新的裂缝和裂缝，或者现有的裂缝和裂缝扩展和扩展，随着时间的推移可能导致渐进的破坏和破坏。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硬度上的不连续性(节理、断层等)、薄弱环节(剪切带、地质接触等)(Hildyard，2007)。高速铁路引起的振动引起的裂纹萌生可能会进一步恶化和破坏开发区。能够预测隧道系统在高速铁路运营期间的反应可能是至关重要的，特别是对于系统的寿命，因此它的弹性。该项目将涉及到对特定的HS2隧道站点进行样本采集的现场工作，对3-D物理模型进行实验测试，以在较小的尺度上模拟真实问题并使用传感器监测系统的响应，以及使用有限元、有限差分、离散元方法进行数值分析。试验结果将被用于数值分析，以建立能够描述隧道结构支撑单元与地面之间的界面响应的本构模型。这个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使用，而且在工业中也是至关重要的。目的和目的主要目的是为了更好地了解高速铁路引起的振动引起的隧道行为。目标包括：-发展描述高速铁路诱发振动期间隧道(地面-支架)系统的力学行为的本构关系-了解振动诱发的机制如何在一系列时间尺度上影响力学行为。-评估这些结果对诸如骨折的长期闭合(或不闭合)等问题的影响

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