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PhD Studentship: Investigating the geomechanics of railway ballast reinforced with micro-geogrids

Infrastructure Group

Location:  Highfield Campus
Closing Date:  Monday 31 December 2018
Reference:  984818AT

Project Reference: CDT-SIS-493

Railway transportation of both freight and people is key to reduce CO2 emissions significantly. There are several advantages of railway transportation; however, minimising track maintenance costs, and finding alternative materials and approaches to improve the performance of railway track is essential. Ballasted railway tracks have generally provided adequate resistance to movement while allowing adjustments in line and level to be made as required (primarily by or during tamping). As the intensity and volume of traffic on railways have increased, more and more maintenance of ballasted tracks has been required. This is disruptive and expensive; hence, more robust ballast and sub-base solutions are being sought.  

Geogrids have been used successfully to reinforce and/or stabilise ballast, as they provide confinement and limit lateral movement of particles, which in turn reduces vertical settlements. Nevertheless, geogrids cannot be used within the tamping area, as they would not survive the tamping process. Recent studies have focused on using polymeric fibres (narrow strips) for reinforcing railway ballast. Full-scale laboratory tests have shown that ballast reinforced with randomly distributed fibres exhibits reduced plastic settlement and greater resistance to irrecoverable settlement than unreinforced solutions. The results also indicate that using fibre reinforced ballast can provide more uniform stiffness and stress distributions across the length of the sleepers.  

This project will focus on studying and designing alternative forms of polymeric reinforcement to extend the track life. In particular, types of inclusions herein designated as micro-geogrids will be investigated. The micro-geogrids will be formed by pieces of geogrid randomly distributed within the ballast. Such solution will take advantage of the reinforcement and stabilising mechanisms of geogrids, while being able to withstand tamping.  

The aim of the project is to investigate the reinforcement and stabilising mechanics of micro-geogrids randomly distributed within ballast. For that purpose, the research will utilise a variety of novel, state of the art techniques (e.g., imaging and sensors, element testing using full field image (DIC) analysis during shearing, full scale cyclic loading tests). During the project, different types of micro-geogrids (optimised form and dimensions) will be produced. The project will also include the development of models to represent the response of ballast reinforced with micro-geogrids, which can inform future guidelines for their optimal design and application.  
The ideal candidate will have background in Civil Engineering, in particular geotechnics and/or soil reinforcement with geosynthetics.  

If you wish to discuss any details of the project informally, please contact Margarida Fernandes de Pinho Lopes, Infrastructure research group, Email: M.Pinho-Lopes@soton.ac.uk, Tel: +44 (0) 2380 59 2383.  

UK students: Full funding is available  

EU students: Full funding may be available or a small top up from the student may be required, depending on the calibre of the student. Funding is competition based and the student must have at least a 2.1 degree or equivalent.  

International students: A small amount of funding is available but the student must be largely self-funded. Funding is competition based and the student must have at least a 2.1 degree or equivalent.

This project is being run in participation with the EPSRC Centre for Doctoral Training in Sustainable Infrastructure Systems: cdt-sis.soton.ac.uk  

For details of our 4 Year PhD programme and further projects, please see http://www.cdt-sis.soton.ac.uk/

To apply, please use the following website: http://www.southampton.ac.uk/engineering/postgraduate/research_degrees/apply.page

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