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

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，主要在中欧存在高速铁路线，2小时内即可行驶500 - 600公里。这种基础设施的需求沿着着技术的进步和对汽车的环保优势以及所遇到的社会效益而上升。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有所增加。铁路隧道尤其是高速铁路隧道的关键考虑因素之一是列车通过时产生的振动的传播。虽然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），但它通常集中在填料和土壤上。在隧道环境中，振动从隧道支架传播到周围岩石或地面，这是一个科学知识的空白。拟议项目旨在更好地了解由于高速铁路引起的振动的启动和传播而导致的隧道行为。更具体地说，该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承受动态载荷时，特别是随着时间的推移，会以不同的方式表现出来。控制其力学行为的主要因素之一是地质学，更具体地说是矿物学含量及其结构特征（Paraskevopoulou，2016，等2017，2018）。在隧道施工过程中，隧道附近的应力会重新分布，从而产生开挖损伤区（EDZ），在该区域中会形成新的裂缝和断裂，或者现有的裂缝和断裂会扩展和扩张，这会导致随着时间的推移逐渐损坏和失效。（振动的）波传播路径直接受后者的影响，因为它取决于不连续性（节理、断层等）、地质背景上的薄弱环节（剪切带、地质接触面等）和断裂刚度（Hildyard，2007）。由于高速铁路引起的振动，EDZ可以进一步恶化和进一步损伤的断裂引发。能够预测高速铁路运营期间隧道系统的反应可能至关重要，特别是对于系统的寿命及其弹性。该项目将包括在特定隧道HS2现场进行样品收集的实地工作，在三维物理模型上进行实验测试，以在较小的尺度上模拟真实的问题，并使用传感器监测系统的响应，以及使用有限元、有限差分和离散元方法进行数值分析。实验测试的结果将被用于数值分析，以开发一个本构模型，可以描述隧道结构支撑元件和地面之间的接口的响应。该项目的最终目标是开发实用的工具和模型，不仅可以在研究领域使用，而且在工业中也是至关重要的。目的和注意事项主要目的是更好地了解隧道行为，由于在高速铁路引起的振动的启动和传播。目标包括：--开发本构关系，以描述高速铁路诱发振动期间隧道（地面支撑）系统的力学行为--了解振动诱发机制如何在一系列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）、长期

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