Balfour Beatty Rail Limited

XiTRACK Polyurethane Ballast Reinforcement – Case Studies

Reference: BBR-2015/1515

Version 15

April 2015

Balfour Beatty Rail Limited a company registered in England under company no. 1982627 with its registered office at 130 WiltonRoad, London, SW1V 1LQ, an agent of Balfour Beatty Group Limited registered in England and Wales, with company registered no.101073, registered office Fourth Floor, 130 Wilton Road, London, SW1V 1LQ.

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Contents1 Introduction .......................................................................................................................... 1

1.1 Lateral Restraint ........................................................................................................... 21.2 Vertical Alignment ......................................................................................................... 21.3 Minimise Ballast Settlement .......................................................................................... 2

2 Applications ......................................................................................................................... 32.1 Business Case for XiTRACK installations ..................................................................... 3

3 Installations .......................................................................................................................... 43.1 Toadmoor Tunnel ......................................................................................................... 43.2 Canal Tunnels............................................................................................................... 43.3 Whiley Hill Masonry Arch Bridge XiSPAN Trial ............................................................. 53.4 University Station, MTR, Hong Kong ............................................................................. 63.5 Famagosta-Assago, Milan Metro, Italy .......................................................................... 63.6 Dalston West Curve transition, East London Line ......................................................... 63.7 Dalston West Curve Sewer, East London Line.............................................................. 73.8 Gravel Hole, West Coast Main Line (Up Line) ............................................................... 73.9 River Lea Under-bridge, North London Line .................................................................. 83.10 East London Line Extension ......................................................................................... 83.11 Kavanaghs Road Bridge Transitions, Brentwood .......................................................... 93.12 Clapham Junction, Windsor Ladder .............................................................................. 93.13 Bletchley Fixed Diamond .............................................................................................. 93.14 Newham Bog .............................................................................................................. 103.15 Peterborough Bridge 184 ............................................................................................ 103.16 Lock Lane Long Eaton, Bridge 3 ................................................................................. 103.17 Kentish Town PACT (Paved Concrete Track) System Transitions .............................. 113.18 Manningtree North Junction ........................................................................................ 113.19 Grove Hill Tunnel, Tunbridge Wells............................................................................. 113.20 Syston North Junction ................................................................................................. 123.21 Knighton Junction ....................................................................................................... 123.22 Keadby Bridge Abutment Reconstruction.................................................................... 123.23 Balavil Burn and Gynack Burn .................................................................................... 133.24 Falkirk Tunnel PACT System Transitions .................................................................... 133.25 Tottenham South Junction .......................................................................................... 133.26 Purfleet Deep Wharf Level Crossing ........................................................................... 143.27 Bletchley ..................................................................................................................... 143.28 Worplesdon Hop Garden ............................................................................................ 143.29 Norwich – Ely .............................................................................................................. 153.30 WCML Bridge Resonance Programme ....................................................................... 15

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1 IntroductionXiTRACK is a visco-elastic polymer which when poured onto ballast forms an in-situ polymer andballast geo-composite. The polymer cures as it penetrates up to a specified depth into the ballastto form a 3-dimensional matrix or ‘reinforcing cage’.

The polymer is applied in-situ by mixing two chemical components through a mixing lance. Thepolymer is poured on to and penetrates into the track ballast. The polymer typically cures within 10to 15 seconds. It achieves 50% of its designed strength within minutes and reaches 90% of itsstrength within 1 hour. The polymer satisfies the requirements of the UK Environment Agency.

Polymers of this type can typically develop strains in excess of 100% before failure in tension. Thebenefit of using the polymer as a reinforcing element, is the ability to design the polymers rheology,strength, stiffness, damping properties and cure rates. The ductility and damping properties of thepolymer make it an ideal material for railway environments where operating conditions can result insudden high dynamic loads (e.g. IRJs, wheel flats and discontinuities). Breakdown of the polymer,is unlikely, however if breakdown occurs it leads to a conventional ballasted ‘state’ and drainage isstill maintained.

Bonding of the polymer to the ballast will occur but this is not critical, as the primary function of thetreatment is to generate polymer-reinforcing elements at every level in the ballast matrix, bothvertically and horizontally, essentially encapsulating the ballast. Bonding of the polymer, to theballast, is not therefore required for the technique to work, which is the fundamental difference withballast gluing where the system’s inherent strength comes from the cohesive bond.

The primary objective of utilising this technology is to maintain track geometry within designedtolerances and reduce maintenance intervention. The design philosophy considers three separatecomponents, lateral and vertical restraint and ballast settlement.

Compressive Strength of Ballast Tensile Strength of Polymer Inherent Geo-composite Strength

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1.1 Lateral RestraintThe XiTRACK system as a solution to maintain lateral alignment is well proven. It has had multipleapplications in similar scenarios to provide restraint on curves, at platforms and through switch andcrossing units.

1.2 Vertical AlignmentThe XiTRACK treated ballast will prevent ballast dilation and hence deterioration (loss of top,maintenance input increase) where interfaces exist such as a structure to ballasted track. It is theintention in this application to provide track restraint and manage track bed stiffness.

1.3 Minimise Ballast SettlementSettlement in ballast is well documented. The XiTRACK treated ballast will not consolidate undertraffic, unlike ballast which is left untreated. Any loss of top or development of twist faults or risk ofdifferential settlement of the superstructure is therefore minimised. In principle the XiTRACKtreated ballast will act as a ground slab reducing the stress concentrations.

The system has several key benefits:

· Very Quick Setting. Replacement of any ballast on top of the XiTRACK layer can occurimmediately after application of the polymer as it sets in seconds. Under normal conditionsXiTRACK can be loaded by site traffic, including vibro-plates, 15 minutes after polymerapplication and by rolling stock 30 minutes after polymer application.

· Long Service Life. The long life characteristics of polyurethanes are well documented. Thedesign is prepared such that the material operates within its yield strength.

· Free Draining. Approximately 30% of the void structure will be occupied by the XiTRACKpolyurethane in treated ballast, leaving the remainder open for drainage.

· Scheme Cost Benefits. XiTRACK is a value engineered solution that will produce life cyclecost benefits. Savings are possible through much reduced compensation payments to TrainOperating Companies and Freight Operating Companies as a direct result of its very rapidinstallation and curing time leading to smaller blockades and disruptive possessions. In additionas it is an engineered ‘solution’ to recurring defects it will help reduce spend on futuremaintenance.

· Can be applied at any time of the year.

· Is designed for the particular project and user requirements.

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2 ApplicationsXiTRACK has a range of designed applications:

· Transitions to and from ballasted track to other track-forms such as slab track and bridgestructures.

· Increasing vertical stiffness of track to reduce or eliminate maintenance problems, or allow anincrease in line speed.

· Removal of “ballast memory” locations

· Protection to structures from impact loads

· Providing a designed resistance to buckling

· Providing a designed resistance to lateral toe loads at Switches and Crossings

· Achieving high fixity for clearances or platform stepping distances

· Washout and flood damage mitigation

2.1 Business Case for XiTRACK installationsThere are broadly two sets of criteria which can be used to make a judgement on theattractiveness of the XiTRACK solution; these are:

· Financial Analysis of the known facts and figures for the asset. This leads to an objective viewof returns, which can be measured against risks to develop a go/no go recommendation.

· Subjective Analysis of the benefits less easy to quantify and the “gut feel” of engineeringmanagement.

Where XiTRACK has been installed the following benefits have been realised:

· Reduced or eliminated infrastructure maintenance

· General acceptance that good infrastructure reduces wear and tear on rolling stock

· Improved long-term track quality

· Improved ride quality

These benefits lead directly to reliability and safety improvements. Quantifying these benefits canbe more difficult than the former but they are generally agreed to exist.

The following examples illustrate how business cases for the installation of XiTRACK have beenarrived at across the full range of job types. The projects described in this paper have all beensubjected to a business case development by the client

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3 Installations3.1 Toadmoor Tunnel

As part of the Midland Mainline Line Speedimprovement Project the line speed throughToadmoor Tunnel was increased from 60 to80mph. Toadmoor has historically been adifficult site to maintain and it was feared aspeed increase would make it more so.XiTRACK was used to create a lowmaintenance high fixity track form was installedin the tunnel. The installation was undertakenin non-disruptive possessions.

3.2 Canal Tunnels

The XiTRACK design was required to providestabilisation to cater for anticipated groundmovement at the Canal Tunnels Sonnevilleslabtrack to ballast interface. Whilst alsoproviding lateral fixity to maintain trackalignment at this critical area.

The complex track geometry and location nextto the concrete slabtrack transition made itparticularly desirable to mitigate trackmaintenance input as far as practicable.

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3.3 Whiley Hill Masonry Arch Bridge XiSPAN TrialNetwork Rail owns and maintains the oldest masonry arch railway bridges in the world. Many arebeyond their design life and are suffering the effects of aging which is increasing the ongoingmaintenance burden.

Balfour Beatty Rail and a team of industryexperts worked with Network Rail to developan innovative, cost effective strengtheningsolution to prolong the life of these criticalassets and preserve their historical legacy.

Balfour Beatty Rail worked with Network Rail toidentify a suitable structure to trial a polymerbased solution on. The bridge in question is atWhiley Hill on the Stockton and Darlington line.Built by George Stephenson in 1824, it ispossibly the oldest structure on the network.

To prolong the life of the structure the team needed to:

· Maintain or increase the capacity of the arch

· Stabilise or reduce the span deflection ratio

· Reduce or eliminate the causes of deterioration

To do this they needed to develop a solution that would:

· Be invisible to the track maintainer

· Have no visible or aesthetic effect on the bridge’s appearance

· Not alter the structural load paths or bridge failure modes

· Be capable of being implemented in short timescales with little or no disruption to traffic

Preliminary analysis and design work indicated that the creation of a geo-composite raft comprisingof ballast and advanced polyurethane, positioned between the track and bridge would addressthese objectives.

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3.4 University Station, MTR, Hong KongXiTRACK was successfully installed betweenthe sleeper end and the platform wall to providelateral resistance to track movement.

In-situ testing on a test installation at Fo Tandepot showed displacements of 0.9mm for100kN sleeper end load.

This installation was completed June 2012.Monitoring to May 2014, has showed amaximum sleeper displacement of 3mm atUniversity station.

3.5 Famagosta-Assago, Milan Metro,Italy

A new extension to the Milan Metro incorporateda concrete slab track underbridge abuttingconventional ballasted track. XiTRACK wasused to combat voiding at the interface. Theinstallation took the form of a ladder structurewith edge beams, locking the ballasted track inposition and controlling track settlement,resulting in a reduced potential for voiding at thesite. The XiTRACK installation was completed inNovember 2010.

3.6 Dalston West Curve transition, East London LineXiTRACK ballast reinforcement was used toreduce the occurrence of voiding at theinterface between concrete slab track andballasted track. The treated section compriseda ‘ladder type’ XiTRACK structure adjacent tothe slab track to reduce voids and dynamicdeflection of the ballasted track. Edge beamswere also installed to give increased lateralresistance to the ballasted track to ensurehorizontal alignment of the ballasted track withthe slab track. These were installed over alonger length than the ladder structure,extending the reinforcement to a vehicle trackcrossing. The XiTRACK installation was

carried out in order to help reduce future track maintenance requirements by reinforcing andstrengthening the ballast and giving transitional track stiffness characteristics. Work wascompleted in August 2010.

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3.7 Dalston West Curve Sewer, East London LineA Victorian cast iron sewer runs under the EastLondon Line at a very shallow depth beneaththe track. XiTRACK was used here in April2010 to transition the track formation over thesewer. The XiTRACK design protects thesewer and prevents the creation of trackmaintenance problems.

3.8 Gravel Hole, West Coast Main Line (Up Line)A section of the West Coast Main Line in Lancashireruns over an area of very poor ground which had leadto the long-term imposition of a temporary speedrestriction. The soft ground lead to critical track velocityand Rayleigh wave induced track maintenanceproblems

XiTRACK formation improvement works wereundertaken in March 2010 with sub-ballastreinforcement provided by the XiTRACK system.Before and after Falling Weight Deflectometermeasurements were taken in order to assess whetherto reopen the line at 125mph line speed.Measurements confirmed that the XiTRACK treatedtrack was working as designed and the line speed waslifted to 125mph.

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3.9 River Lea Under-bridge, North London LineThis site was historically a maintenance problem due to asudden track stiffness change between this bridge and theadjacent embankment. XiTRACK was used to create aconstant rate of change of stiffness between the bridgeand the embankment.

The work took place over Christmas 2009, and involvedapplication of XiTRACK in gradually higher concentrationsapproaching the bridge over a predetermined distance.This graded the stiffness of the track to match the bridgeby providing a varying degree of vertical reinforcement.The scheme left a layer of ballast between the bottom ofthe sleepers and top of the XiTRACK treated ballast inorder to allow the normal tamping regime to continue.

3.10 East London Line ExtensionExtensive XiTRACK work was undertaken on the East London Line in August 2009. The workincluded vertical track reinforcement on the Surrey Canal Road Line and on the New Cross Flyoverand increasing track fixity through stations.

The Surrey Canal Road Bridge had presented the project with a problem as switches andcrossings were to be positioned spanning the interface between a bridge and an embankment. Itwas therefore necessary to have a solution that protected the switches and crossing from thermalmovement of the bridge and varying track support stiffness. These objectives were achieved bycreating a XiTRACK raft of reinforced ballast under the switches and crossings.

The XiTRACK technique was also used successfully to reinforce and stabilise the ballast betweenthe sleeper end and the platform wall at stations on the East London Line, increasing the trackfixity at these locations.

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3.11 Kavanaghs Road Bridge Transitions, BrentwoodIn order to help prevent voiding at the interfacebetween a longitudinal timber bridge and plain-linetrack, XiTRACK ballast reinforcement was used ina ‘ladder type’ structure near the bridge/ballastinterface. The purpose of this treatment was toreduce voids close to the bridge through 3-dimensional ballast reinforcement and to provide agraduated ballast stiffness (within thegeocomposite) to help reduce track deflection fromthe ballast dynamic response.

The XiTRACK installation was carried out in orderto help reduce future track maintenancerequirements by reinforcing and strengthening theballast and giving transitional track stiffnesscharacteristics. Work was completed in July 2009.

3.12 Clapham Junction, Windsor LadderClapham junction is one of the busiest railwayjunctions in the world. Because of this, access forinspection, maintenance and repair is very limited.XiTRACK was chosen at this location to increasethe Reliability, Availability, Maintainability(“RAMS”) requirements of the Windsor Ladder.

3.13 Bletchley Fixed DiamondFollowing on from the continuous satisfactoryperformance of XiTRACK that was installed atsome Switches and Crossings several yearsearlier, the Track Maintenance Engineer utilisedXiTRACK to address voiding problems beneath afixed diamond that had lead to a speed restrictionand increased maintenance intervention. A padwas constructed to give uniform stiffness to alayer of ballast beneath the bottom ballastenabling tamping activities to be unaffected.

The work was carried out in time for the temporaryspeed restriction in place to be removed, ready foran increased service frequency.

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3.14 Newham BogHere the East Coast Main Line rail route north ofNewcastle runs across a section of very poorground. A long history of problems had beenencountered at the interface with a boulder clayformation and a line speed reduction wasnecessary owing to the low Critical TrackVelocity at the site. XiTRACK PolyurethaneBallast Reinforcement was used to stiffen up theformation to provide a graded change from theboulder clay to the soft peat bog, replacinggeocells which were installed in the 1980’s.

3.15 Peterborough Bridge 184XiTRACK was specified as part of the plain linetrack renewal works as a means of managingtrack stiffness at the interface with a longitudinaltimber bridge. XiTRACK was applied to thebottom ballast with the track in-situ as a meansof preventing future track quality problems andvoiding.

3.16 Lock Lane Long Eaton, Bridge 3This was a maintenance scheme to prevent thereturn of ongoing track quality issues at thislocation. Along with the renewal of thelongitudinal timbers on the bridge, XiTRACKwas applied on the approaches and run offs withthe existing track in-situ to prevent track voidingat the interface with the structure.

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3.17 Kentish Town PACT (Paved Concrete Track) System TransitionsAt this location the existing concrete transitionstructures between the slab and ballastedtrack were beginning to fail and proving to be amaintenance problem. They were replacedwith a XiTRACK design that enabled ordinarytrack components to be used right up to theinterface with the slab thus considerablyreducing the maintenance burden.

A design, project management and installationscheme was carried out successfully duringthe associated plain line track renewal.

3.18 Manningtree North JunctionHere the change in track stiffness from astructure to an embankment and then to anunder bridge was causing track qualityproblems, particularly at the interface withSwitches and Crossings at the junction. Duringthe junction’s renewal the opportunity wastaken to install a layer of XiTRACK sub ballastwith a varying stiffness, designed to grade outthe hard spots caused by the structures.

3.19 Grove Hill Tunnel, Tunbridge WellsThis major construction scheme saw thereplacement of approximately 120m of failedslab track system which had originally beeninstalled to maintain tight clearances throughthe tunnel but had failed owing to drainageissues. A bed of free draining XiTRACKtreated ballast was used instead with acollector drain running along the centre. Thetrack was laid on this and the clearancesmaintained by means of XiTRACK edgerestraint beams.

This scheme has solved the drainage issuesoriginally present on site and continues toperform well.

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3.20 Syston North JunctionHere lateral track stability problems areaggravated by the tight radius of the turnoutwhich, although the line speed is relatively low,does lead to significant lateral forces.

End restraint plates had been used but failed tomaintain the alignment and so an alternative wassought.

XiTRACK application was completed withinschedule and subsequent monitoring hasconfirmed that the treated areas have performedas expected.

3.21 Knighton JunctionXiTRACK treatment was designed to give apolymer loading leading to a maintainable,improved alternative to end-plates for improvingthe lateral stability of the junction.

XiTRACK polymer application was completedwithin schedule and subsequent track recordingtrain runs show the alignment to be satisfactorilyretained.

3.22 Keadby Bridge Abutment ReconstructionKeadby was another major construction schemewhere XiTRACK was utilised. The bridge wasreplaced in 2003 and since construction therehad been alignment problems due to movementswithin the abutments and substructure arisingfrom train loading and bridge movements. Duringthe planned renewal of the abutments during ablockade over Christmas 2006, XiTRACKtreatment was applied to produce geo-compositereinforcement of the transitions on both the Eastand West abutments at this important structure.

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3.23 Balavil Burn and Gynack BurnTwo bridges on the Highland Main Line atGynack and Balavil near Kingussie are prone toflooding causing heavy ballast contamination andpotential wash-out, leading to track defects,disruption and subsequent delays.

A XiTRACK scheme was devised for each of thebridge transitions to help prevent ballast beingwashed out under the sleepers during suchperiods of flooding. This gives protection to theballast under the sleepers permitting any waterto pass through the geocomposite but allows allforms of conventional maintenance to occur.

The jobs were completed on time and each site now has proven enhanced protection againstballast wash-out.

3.24 Falkirk Tunnel PACT System TransitionsIn order to reduce the dynamic load on the run-on to the concrete slab-track, a stiffenedtransition was necessary. It was known that theconcrete track transition structure haddeteriorated and in addition the site sufferedfrom water ingress problems and the XiTRACKdesign had to accommodate these effects.

A suitable XiTRACK design was installed andperforms as expected.

3.25 Tottenham South JunctionA complex scheme of vertical and lateralXiTRACK reinforcement of the transition areawas designed to improve the performance underlocal heavy passenger and freight loading andparticular attention was paid to the ballast on thebridge deck itself near to the toes of theSwitches and Crossings.

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3.26 Purfleet Deep Wharf Level CrossingThe level crossing was showing signs of bearingfailure, pocketing and rutting due to the weakformation and the very soft Alluvium claysknown to exist in the sub grade. In view of thecurrent and anticipated future loadingconditions, along with needing to minimise lineclosure time, a XiTRACK treatment wasconsidered desirable in order to provide a long-term cost effective solution.

A XiTRACK design was prepared for the siteand polymer applied in the specified loadingpattern and, including all groundworks, the sitewas returned to full rail and road traffic after atotal closure time of only three days.

3.27 BletchleySwitches and Crossings at Bletchley weretreated to correct vertical and lateral stabilityproblems on this high-speed section of the WestCoast Main Line. The site had been a majormaintenance headache for some time withimposed speed restrictions until XiTRACK wasapplied.

This site continues to perform and led toadditional schemes being implemented in thesurrounding area.

3.28 Worplesdon Hop GardenThe XiTRACK technique was used to reinforceand stabilise the vertical bridge transitions forthe Hop Garden Bridge on the Up Guildford linenear Worplesdon Station. XiTRACK was used tostabilise the transition in its current configurationto help prevent further deterioration of the trackgeometry. The site was treated to allow fullmaintenance if required using manualtechniques.

No vertical re-alignment has been required sincetreatment.

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3.29 Norwich – ElyXiTRACK treatment removed the persistentlateral track faults around these transitionswhere tamping is difficult or impossible and nolateral re-alignment has been needed since theapplication.

The treatment area was adjacent to a river andall requirements of the Environmental Agencywere met.

3.30 WCML Bridge Resonance ProgrammeXiTRACK Polymer was applied to ballast on aseries of bridges on the West Coast Main Linein Network Rail’s Test Site A, in the TrentValley and in Scotland.

The bridges in the series were usually basedon a steel plate decking and had been found tobe subject to pre-resonance problems atnormal passenger train speed. They had beenshown to be susceptible to ballast movementdue to induced excitement with consequentloss of track alignment. This problem had beendemonstrated to be likely to get worse withPendolino increased line speeds.

This was an effective temporary solution until the XiTRACK was broken out during the renewal ofthe bridges during the upgrade of the route.

Contact Details

Dermot Kelly

Balfour Beatty Rail Limited

Telephone: +44 (0) 7967 668 929

Email: Dermot.Kelly@bbrail.com

www.bbrail.co.uk

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