Modelling of Train Induced Vibration (MOTIV)

In spite of the global financial and economic crisis, a large number of plans for new railway networks is being proposed to meet the demand for both passengers and freight rail services. For example, construction has commenced on the £15.9 billion Crossrail project to provide an East-West rail link under London with 22 km of tunnels under the city. In January 2012 phase 1 of High Speed 2 (HS2) project was given government approval. The project will connect between London and Birmingham with future extensions to Leeds and Manchester. The overall cost of the line connecting between London and Birmingham is estimated between £15.8-17.4 billon. This will include substantial tunnelled sections through urban areas. Plans for light rail lines in urban areas are also progressing. In December 2011, plans to extend the Nottingham tram line where given green light by the government. The project involves 2 new tram lines with overall cost of £570m. In February 2012, Centro was given the green light to go ahead with the extension of Birmingham's Midland Metro tram service in a project worth £128 million.

The introduction of surface and underground railways provides substantial reduction of pollution resulting from the use of trains powered by electricity and the reduction of number of cars on streets. The use of underground railways helps significantly with congestion problems in urban areas. One of the main environmental issues linked with railway transportation in urban areas is ground-borne vibration transmitting to nearby buildings. Ground-borne vibration from railways is generated at the wheel-rail interface due to the passage of individual wheels on tracks (quasi-static loading) and due to irregularities of wheels and tracks (dynamic loading). Vibration propagates to nearby buildings where it causes annoyance to people and malfunctioning of sensitive equipment. Inhabitants of buildings perceive vibration either directly, due to motion of floors and walls, or indirectly as re-radiated noise. Vibration can also cause disturbance due to movement of household objects, especially mirrors or due to rattling of windowpanes and glassware. The problem can be more serious in some circumstances, such as when an underground tunnel passes below sensitive buildings such as a concert hall.

This project aims to develop a better understanding about key issues regarding the generation and propagation of railway vibration, namely the non-linear behaviour of tracks' elements and the dynamic soil-tunnel-pile interaction for a single as well as a twin tunnels. This will lead to improved models for the prediction of ground-borne vibration and noise from railways in order to reduce prediction uncertainty. To achieve the aim of the project, three objectives are set. The first is to investigate the effect of pre-load and non-linear behaviour of resilient elements of tracks will be investigated using excitation models (i.e. tracks on elastic foundations). The second is to develop a detailed Periodic Boundary Element model and couple that to the relevant structural elements to account for the interaction between twin-tunnels, soil and pile foundations. The third is to develop a fast running tool for calculating vibration transmitted to buildings on pile-foundation from surface tracks and from tracks in tunnels embedded in multi-layered ground. The model will be built in friendly-user software that will be made available for engineers responsible for designing of railway infrastructure and for engineers responsible for designing of measures to reduce vibration from railways.

Note that the project does not aim specifically to address the issue of vibration from high speed trains running on soft soil but is focused rather on vibration and noise from trains in urban settings, principally in tunnels.

For new railway projects, such as Crossrail and HS2, the mitigation of ground-borne noise and vibration is a major concern and can form a significant part of the project costs. Reducing uncertainty in the predictions can lead to significant savings due to a reduction in the need for special trackforms or building isolation. Reducing ground-borne noise and vibration is one of the main priorities for local government bodies responsible for transport systems in the UK. This is exemplified by the strategies of the Mayor of London 2000-2008 for the Transport for London to develop cost-effective plans to minimise noise and vibration through improvements in the design, operation, monitoring and maintenance of transport infrastructure. In 2011, the European Rail Research Advisory Council (ERRAC) issued a roadmap fact sheet entitled Greening of Surface Transport that states "The European railways will strive towards noise and vibrations no longer being considered a problem for the railways and its neighbours - meaning that noise and vibration levels are socially and economically acceptable and allow for 24-hour passenger and freight operation by 2050". One of the objectives defined in the Strategic Rail Research Agenda (SRRA) 2020 issued by ERRAC points out the urgent need to better understand the propagation and attenuation of vibrations transmitted from subway tunnels.
This project will deliver both knowledge and numerical tools that will lead to significantly greater understanding and improved accuracy for predictions of ground-borne vibration from railways. Those more accurate tools are also needed for the assessment of existing railways and for the design of mitigation methods before these are implemented. The right choice of mitigation method and its specification is crucial because of the high financial cost and the difficulty of retrospective replacement. The research proposed will also provide scientific input to allow the preparation of International Standards and will help prepare good practice guides for the design of surface and underground railway operation to maintain minimum vibrations for the lifetime of operation. This will have a significant impact on quality of life for people who live near railway lines.
The project will be strongly supported by a stakeholders group with keen interest in the project and its deliverables as evidenced by the letters of support. The stakeholders group involves representatives from metro operators; infrastructure owners; track component manufacturers; consultants and contractors; and world-class academics. The stakeholders group will provide inputs to the work, advise on technical issues and identify ways to maximize the impact.