GRAFT II Test Rail Rig

The Railway Research team have been involved in rail track development for over a decade. We investigate the issues facing modern rail networks as they have to cope with more traffic, heavier loads and higher speeds.

Academics at the Institute for Infrastructure and Environment are at the forefront of research into solving these problems.

Using our test facilities and software developed at Heriot-Watt we can offer numerical and experimental analyses of rail track under many different simulated conditions.

Our software looks primarily at the behaviour of rail track when it is under high speed conditions and compares a number of variables including track composition. It predicts where likely displacements and faults in the track will occur and allows users to simulate numerous conditions which would affect the track's performance. It can model dynamic ground wave propagation.


Railway track settlement is a serious problem in modern day railway engineering and has considerable cost and time implications to the rail industry through maintenance operations, track reconstructions and line speed restrictions. The main cause of track deterioration is settlement of the substructure and a point is eventually reached where track geometry has to be improved before differential track settlements give rise to faults. The Geo-pavement and Railways Accelerated Fatigue Testing facility (GRAFT) is one of only two academic facilities of its kind in the UK. It has a hydraulic capacity of 200 tonnes (150 tonnes cyclically) which enables accelerated testing of existing and new railway products in realistic railway conditions. It is important for all proposed solutions to railway track settlement to be researched thoroughly to understand the implications of placing them within the harsh substructure environment of railway tracks. The GRAFT facility at Heriot-Watt University has been developed to enable the performance of these solutions to be quantified and compared with confidence.

Track Geometry

The patented polymer technology, XiTRACK, which was developed at Heriot-Watt has been widely used by industry across a number of high profile sites. The polymers are used to reinforce ballast and they form an interconnected, energy absorbing network which continues to allow drainage. Due to the commercial nature of the polymer, the technology was ‘spun-out' to an external partner who have continued to work successfully with the team to develop the product.

The technology was developed in 2000 and was first used in March of that year at Bletchley to reinforce a switch and crossing which had been regularly going out of alignment every three months. The polymers were installed at the site for ten years and did not require any further maintenance. It was such a success that there have been two further installations on nearby track. After five years of test installations, Network Rail approved the technology which is now used across the country. It has been used to stabilise bridges and tunnels; turnouts; slab-track transitions; level crossings; poor track formations; expansion joints; and to alleviate issues with tolerance between trains and tunnels.

There have been over 50 installations since its development including a high profile project at Clapham Junction. A major benefit of the polymers is that they are fast setting so cause minimal disruption to traffic; they achieve 90% stiffness within the first hour of application.

The site installation equipment is compact and can easily be transported to and from the site of application. Another example of a successful installation of the polymers was at Newham Bog on the East Coast Mainline. This track was constructed over peat bogs which created severe track deflections and significant track issues. The line is part of the High Speed network which carries transport travelling up to 125 miles per hour. Since the application of the technology, there has been a significant improvement in track quality.

The technology has proven to be extremely successful in solving a multitude of railway track problems, and it has significantly reduced maintenance at many sites that have been reinforced over the last decade. The large range of application profiles for the technology and the fact that it can be used on all ballasted track at low temperatures means that it will continue to play an important part in the upgrading of Britain's rail network. The technology is installed by Balfour Beatty Rail.

Contributing staff

The group is made up of several academics, researchers and students at the School as well as being part of a collaborative partnership with Edinburgh University.

Members from the School of Energy, Geoscience, Infrastructure and Society are:

  • Dr Gabi Medero
  • Professor Omar Laghrouche
  • Dr David Connolly
  • Dr Benny Suryanto
  • Dr João Pombo