Underground railways can be a particularly significant source of ground-borne vibration. Vibration is generated at the wheel-rail interface, from where it propagates through the trackbed, into the ground and on and up into nearby buildings. Although it is unlikely to cause structural damage, the disturbance caused to building occupants and the disruption caused in specialist buildings, such as hospitals and research facilities, can have significant social and economic consequences.
It has become apparent that some locations suffering from unacceptable increases in vibration levels are associated with areas of the railway network where rail roughness- the primary cause of vibration- is known to have remained unchanged. This has led to speculation over what may be causing the increased levels. Recent work has concluded that subterranean property developments, such as building foundations, water/sewage tunnels and underground basements, have significant potential to modify the existing ground vibration field, redirecting vibration energy to previously undisturbed buildings. As a result, the potential of such developments to exacerbate ground-borne vibration is to be reflected in the forthcoming revision of the London Plan, to encourage a more responsible approach to development; in particular, to create an expectation that future developments are accompanied by environmental impact assessments that explicitly consider the effects on the ground-borne vibration environment. To help facilitate the required assessments, as well as informing potential revisions to the planning process, there is a clear and urgent need for new guidance.
This research project will apply fundamental engineering science, underpinned by site measurements, to develop a full understanding of the problem, as well as investigate potential mitigation measures. The project has three broad objectives.
A theoretical study will be undertaken to understand fully the nature of the problem; in particular, to quantify the changes in ground-borne vibration levels associated with the construction of a range of typical subterranean structures in the vicinity of an underground railway tunnel. A range of semi-analytical and numerical models will be used, beginning with highly idealised models and gradually adding complexity to build up an understanding of the fundamental dynamic behaviour. The research will build upon the well-established PiP model, as a computationally-efficient tool for calculating the vibration field from an underground railway, as well as recent work in the area of soil-structure interaction and boundary-element modelling to model the dynamic response of structures coupled to the ground. The research will be designed to enable the development of practicable guidance, together with the analysis tools that are anticipated as being necessary for practitioners to assess/develop proposed designs.
In addition to developing the necessary analysis tools, the research will investigate potential mitigation methods for the particular problem of new basement structures. Conventional techniques used in the vibration isolation of buildings will be used as the basis for investigating ways in which the impact of new basements may be mitigated. This includes the potential incorporation of elastomeric material within the outer walls of basement structures to minimise wave reflections.
Site measurements are seen as an essential component of the research, to assist with model validation and to help quantify the 'added-basement' effect. It is anticipated that measurements will be done in collaboration with Transport for London, and other existing industrial partners, and take advantage of current work in the Department that is developing novel, low-cost instrumentation for the widespread monitoring of ground-borne vibration in the field.
The project is funded by EPSRC and Farrat Isolevel Ltd, a leading designer and manufacturer of vibration isolation solutions for buildings. The research will be conducted in close collaboration with Farrat and associated partners, to ensure that the project leads to practical implementation wherever possible.
Applicants should have (or expect to obtain) the equivalent of a UK first class honours degree (and preferably a Masters degree) in Mechanical or Structural Engineering. Preference will be given to those with experience in Structural Dynamics.
EPSRC DTP studentships are fully-funded (fees and maintenance) for UK students or provide fees only for EU students from outside the UK. Further details about eligibility can be found at: https://epsrc.ukri.org/skills/students/help/eligibility/.
Expressions of interest, indicating nationality and funding status, together with a CV and the names and contact details for two referees, should be sent to Dr James Talbot (firstname.lastname@example.org). Provisional closing date: 28th June 2019, but earlier application is advised.
Please note that any offer of funding will be conditional on securing a place as a PhD student. Thus, selected Candidates will need to apply separately for admission through the University's Graduate Admissions application portal; this can be done before or after applying for this funding opportunity. Note that there is a £60 fee for PhD applications. The applicant portal can be accessed via: www.graduate.study.cam.ac.uk/courses/directory/egegpdpeg.
The University actively supports equality, diversity and inclusion and encourages applications from all sections of society.