01 - Increasing the efficiency of Railway Track Maintenance through Ballast Reinforcement
Submitting InstitutionsHeriot-Watt University,
University of Edinburgh
Unit of AssessmentGeneral Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Mathematical Sciences: Applied Mathematics
Engineering: Civil Engineering
Summary of the impact
ERPE, through the application of XiTRACK technology (using advanced
polyurethane polymers to reinforce the ballast matrix, enhancing strength,
stiffness and resilience) — has reduced track maintenance by a factor of
up to 40, increased maintenance intervals from 3-monthly to 10 years with
track speeds increased up to 125 mph in critical sections of the UK, Italy
and Hong Kong rail networks. Developments in Finite Element (FE)
geomechanics related to Rayleigh waves are used by HS2; and FE backed
artificial neural networks are informing US High Speed operators on ground
borne vibrations. The financial impact of XiTrack is estimated at least
£50M; and avoidance of Rayleigh wave problems and ground borne vibration
mitigation, in the region of £10M; plus benefits to millions of
The key researchers were: Prof Woodward, Prof Forde, Prof Laghrouche, Drs
Connolly (L/ECR/formerly PGR), Giannopoulos (SL) and Medero (L). All
researchers were active throughout the underpinning research period.
Overall, the three most important research activities from the ERPE
research which enabled the impacts in XiTRACK and Railway Engineering
- ERPE's (Woodward, Laghrouche and Medero) work in the numerical
modelling of granular soils, in particular large diameter aggregates and
their behaviour under cyclic loading (1993-2000) led to an examination
of techniques that could reinforce geo-materials to improve performance.
Woodward, aware of the use of polymer reinforced mortars for road
cobbles, made the connection through to railways; he then developed and
patented [P1] the XiTRACK technique using advanced polyurethane
polymers. The rigour of the research behind XiTrack is underlined by
Woodward's progression from a concept to authorship of a bespoke 3-D
track focused FE software, DART3-D, verified by large scale laboratory
experiments in GRAFT Rigs 1 and 2, and field proven on Network Rail
track in the UK and latterly with field trials in Italy and Hong Kong in
conjunction with Balfour Beatty Rail [S1]. This research to practice to
industry take-up has provided new understanding of the year round,
seasonal variations performance of polymer/XiTRACK stabilised ballast on
actual site operational live track. [1-4].
- Work on numerical analysis methods by ERPE (Woodward, Laghrouche,
Forde and Connolly) using DART3-D to examine the geodynamic behaviour of
high-speed trains developed the concept of the ground Mach Cone as the
train velocity approaches the Rayleigh wave velocity - thus generating
large vertical track displacements which disturb the train's ride
quality and stability. Further analysis shows the significance of the
rolling stock and power unit suspensions longitudinal location layouts
on the development of the mach cone as the train approaches the Rayleigh
wave velocity. It shows that there is not a unique soil-structure
"critical velocity", but rather a soil-structure-rolling stock
configuration interaction. This reinforces the need for a non-linear 3-D
FE analysis rather than a more simplistic 2-D analysis taking limited
account of suspension geometry. This work led to EPSRC funding [G1] on
high- speed track design and in turn led to consultancy for HS2 by
Woodward. Two TSB grants on Rail Innovation ([G2] and [G3]) have also
been funded. [3-4]
- ERPE research [G1] into high-speed rail has been used to reduce ground
vibrations. Forde, Giannopoulos and Connolly have focused on ground
borne vibrations emanating from high-speed trains and involved extensive
field monitoring trials in the UK (HS1) and Belgium funded by NERC [G4].
This work strengthened the international database and enabled Abaqus 3-D
FE models (run on a supercomputer) to be accurately calibrated. The work
demonstrated that the widely used (US) Federal Railroad Administration
(2005) software to predict ground borne vibrations is simplistic and
inaccurate. A more accurate, simple ground borne vibration demonstration
model using neural networks based on the Abaqus models and verified by
the UK/HS1 and Belgian data collection is now freely available
This work has been extended to provide design guidelines for vibration
mitigation using trenches backfilled with a low acoustic impedance
References to the research
References identified with * are those which best indicate the quality of
the underpinning research
*Woodward, P.K., Thompson, D. and Banimahd, M. "GeoComposite
Technology: Reducing The Railway Maintenance." Proceedings of the
Institution of Civil Engineers, Transport Journal, Vol. 122, Part 3, pp.
135-139 (2007). DOI: 10.1680/tran.2007.160.3.109
Won 2008 Institution of Civil Engineers Best Paper Award, Webb
Prize, Transport Journal. The paper describes application of the
technology to reducing ground vibration.
*Woodward, P.K., Kennedy, J., Medero, G. and Banimahd, M. "Application
Of In-Situ Polyurethane GeoComposite Beams To Improve The Passive
Shoulder Resistance Of Railway Track." Proceedings of the
Institution of Mechanical Engineers, Part F, Journal of Rail and Rapid
Transit, Vol. 226, Issue 3, pp. 294-304 (2011). DOI: 10.1177/0954409711420521
The paper discusses application of the technology to reducing track
misalignments at switch and crossings.
 Woodward, P.K. El-Kacimi, A., Laghrouche, O., Medero. G. and
Banimahd, M."Application Of Polyurethane GeoComposites To Help Maintain
Track Geometry For Ballasted High-Speed Railway Tracks" Journal of
Zhejiang University-SCIENCE A (Applied Physics & Engineering), Vol.
226, Issue 3, pp. 257-271 (2012). DOI: 10.1631/jzus.A12ISGT3
Discusses application of the technology to high-speed issues, in
particular to bridge transitions.
 Kennedy, J., Woodward, P.K. and Medero, G. "Reducing Railway Track
Settlement Using Polyurethane Polymer Reinforcement of the Ballast."
International Journal for Construction and Building Materials, Vol. 44,,
pp. 615-625 (2013). DOI: 10.1016/j.conbuildmat.2013.03.002
The paper presents experimental data using GRAFT I to prove that the
technology reduces track settlement over soft soils.
 Connolly, D., Giannopoulos, A. and Forde, M.C. ".Numerical
modelling of ground borne vibrations from high speed rail lines on
embankments", Soil Dynamics and Earthquake Engineering, Vol. 48, pp.
13-19 (2013). DOI: 10.1016/j.soildyn.2012.12.003
3-D finite element analysis of high speed trains (HST) running on an
embankment, using Abaqus. was correlated with published data from HST in
*Connolly, D., Giannopoulos, A., Fan, W., Woodward, P.K. and Forde,
M.C, "Optimising low acoustic impedance back-fill material wave
barrier dimensions to shield structures from ground borne high speed
rail vibrations", Construction and Building Materials, Vol. 44, pp.
557 - 564, DOI: 10.1016/j.conbuildmat.2013.03.034
First paper to consider the acoustic impedance of back-filled wave
barriers to interrupt ground borne vibrations from High Speed Trains (HST)
— it would enable the UK project HS2 to reduce vibrations in sensitive
[G1] EPSRC, EP/H027262/1 & EP/H029397/1, £479k, Woodward, Forde,
Lagrouche, Medero, Giannopoulos, "Development of Design Guidelines for
High-speed Railway Track Including Critical Track Velocities and Track
Mitigation Strategies", 2010-2013.
[G2] TSB, #101204, £230k, ERPE, University of Sheffield, Balfour Beatty
Rail Technologies Ltd., "XiSPAN Bridge Strengthening and Life
[G3] TSB, #101199, £297k, ERPE, Balfour Beatty Rail Technologies Ltd., "Formation
Stiffness Measurement", 2012-2013.
[G4] NERC, Geophysical Equipment Facility Loan, 971, Forde, "Seismic
Vibration Measurements near High Speed Railway lines, to validate
University of Edinburgh developed software", 2012.
[P1] PCT/GB01/03679 Woodward, P.K. and Moss, R.M. `Method of
Stabilising Particulates' International Patent Number WO 02/16695 Al
Details of the impact
The invention and patenting of the XiTRACK technique led to the
development of new innovative technologies to solve long-standing railway
track problems, such as transitions, switch & crossing faults, track
tolerance issues etc. In 2001, 2Ei Ltd, which is a spin out company from
ERPE, formed a joint venture company (XiTRACK Ltd) with Hyperlast Ltd. In
2003, XiTRACK appointed Balfour Beatty Rail Ltd as the preferred
Implementation of XiTRACK across the UK railway network (and now
overseas) demonstrates the application of new technology in engineering
practice, from theory through to actual site application. It led to patent
[P1] being filed in 2001 which resulted in the technology being adopted
into the Network Rail (UK) procedures for the solution of ballasted track
problems (Network Rail Approval Certificate No. PA05/01995) [S2]. XiTRACK
allows accurate control of track forces, settlements and transient
deflections. What this means is that the track is enhanced in terms of
engineering performance and designability. XiTRACK is not applied across
long stretches of track, as it resolves site specific problems, where
stability and issues of track downtime are critical.
The Technique has been applied at many strategically important sites
across the UK including tunnels, switch and crossings. Some examples of
application are listed below:-
- Newham Bog: XiTRACK was used to stabilise the trackbed at Newham Bog
on the East Coast Main Line in 2008 to prevent excessive track
maintenance and hence improve track usage. The cost of installation of
the XiTRACK element of the track work was £250,000 and to date
performance has been very good [S1].
- Manningtree North Junction: XiTRACK was used to stabilise the track
over an embankment containing switch and crossings situated on the
Colchester to Ipswich line in 2008. The solution has significantly
reduced track maintenance at the site [S1].
- XiTRACK was used to stabilise two adjacent high-speed switch and
crossings (2000 and 2008) at Bletchley South on the West Coast Main
Line. At the first site 10 years of maintenance free operation (normal
maintenance period was every 3 months ) was observed and at the
second site the system was installed to prevent the repeated failure of
the switch and crossing, i.e. to stop the formation of rail cracking.
The West Coast Mainline carries 75 million passengers per annum and 48%
of all UK freight traffic (trains) [S1].
- The technology was used to stabilise the track bed at Clapham Junction
in December 2008. It is one of the most important and highly used
railway junctions in Europe with over 2,500 trains passing through
Clapham Junction every day  [S1].
- In 2009, it was applied at Hoxton Station on the East London Line to
provide a high fixity solution (within 0.06in [1.5mm] movement) to
ensure that gauge clearances are maintained and hence track safety
assured. This track forms part of the line that was used to support the
2012 London Olympics  [S1].
The sites listed above are critical sites to the operation of the UK rail
network and the final site was critical to the transport of passengers for
the London 2012 Olympics.
The technology is being developed by one of the world's largest chemical
companies, The Dow Chemical Company, and by one of Europe's largest
railway (and construction) companies Balfour Beatty. It has led to new
staff appointments at these companies: in Dow Chemicals, polymer chemists
and marketing; in Balfour Beatty Rail sales, technical and track
installation teams [S1]. The technique has therefore gone full course,
i.e. it was developed at ERPE as a new technology, patented by ERPE,
spun-out of ERPE into industry, trialled for a period of 6 years through a
licensing agreement, obtained approval certificate by Network Rail and is
now used to solve real track problems, including critical sites to the
operation of the UK's rail and transportation infrastructure. Since 2011
the design process has been formally adopted by Balfour Beatty Rail Ltd to
design XiTRACK track treatments for polyurethane treated sites both in the
UK and overseas, specifically in Italy (Milan Metro slab-track to ballast
transitions 2011) and Hong Kong MTR Station for lateral clearance issues
(University Station May 2012)[S1]. The Hong Kong MTR operates over 1.5
billion passenger journeys per year.
This research has significant impact in the development of ballasted
high-speed networks. This pioneering work is of particular interest to the
development of the UK High Speed 2 line and hence Woodward has been
appointed as a high-speed track consultant to HS2. Strong industry
interest is demonstrated by ERPE consultancy from HS2 [S5] and the
Transport Select Committee discussing ERPE research [S6].
The advanced geomechanics numerical modelling work demonstrated that the
widely used (US) Federal Railroad Administration (2005) software to
predict ground borne vibrations is simplistic and inaccurate. The key
output creating international impact was a more accurate, simple ground
borne vibration demonstration model using neural networks based on the
Abaqus models and verified by the UK/HS1 and Belgian data collection which
is now freely available
"The numerical analyses and ground borne vibration predictions from
High Speed Trains (HST) are particularly important to geotechnical
engineers involved in HST track design in the USA. The creation of the
freely available through a weblink to predict these vibrations has had a
substantial impact." [S7].
ERPE has established a Centre of Excellence in High Speed Railways in
partnership with Atkins Global Plc. (one of the world's largest
engineering consultancies) [S4]. Atkins Global is working closely with
ERPE and Woodward has been appointed to the Atkins Chair of High Speed
Railways and has built the UK's largest laboratory railway test track
[S3], which complements the largest full scale outdoor railway test track
at a UK university at the Kings Buildings campus.
Sources to corroborate the impact
[S1] Head of Systems and Technology, Balfour Beatty Rail will confirm
that Balfour Beatty Rail works with ERPE in the field of railway
which outlines how Balfour Beatty Rail apply XiTRACK technology and
confirms full Network Rail Product Acceptance.
[S3] Business Development Manager, Atkins Global who will outline how
Atkins Global view the research and its application in a High Speed rail
which confirms Atkins Global Plc.'s establishment of a Centre for
Excellence with ERPE.
confirms Woodward's HS2 consultancy
confirms discussion of ERPE research relating to HS2 at the Transport
Parliamentary Select Committee, item 26.
Numerical Geomechanics — Ground Borne Vibrations:
[S7] Senior Consultant, GEI Consultants, Inc -. See comments in section 4