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 Wilton Road, 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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Contents

1 Introduction .......................................................................................................................... 1

1.1 Lateral Restraint ........................................................................................................... 2

1.2 Vertical Alignment ......................................................................................................... 2

1.3 Minimise Ballast Settlement .......................................................................................... 2

2 Applications ......................................................................................................................... 3

2.1 Business Case for XiTRACK installations ..................................................................... 3

3 Installations .......................................................................................................................... 4

3.1 Toadmoor Tunnel ......................................................................................................... 4

3.2 Canal Tunnels .............................................................................................................. 4

3.3 Whiley Hill Masonry Arch Bridge XiSPAN Trial ............................................................. 5

3.4 University Station, MTR, Hong Kong ............................................................................. 6

3.5 Famagosta-Assago, Milan Metro, Italy .......................................................................... 6

3.6 Dalston West Curve transition, East London Line ......................................................... 6

3.7 Dalston West Curve Sewer, East London Line ............................................................. 7

3.8 Gravel Hole, West Coast Main Line (Up Line) ............................................................... 7

3.9 River Lea Under-bridge, North London Line .................................................................. 8

3.10 East London Line Extension ......................................................................................... 8

3.11 Kavanaghs Road Bridge Transitions, Brentwood .......................................................... 9

3.12 Clapham Junction, Windsor Ladder .............................................................................. 9

3.13 Bletchley Fixed Diamond .............................................................................................. 9

3.14 Newham Bog .............................................................................................................. 10

3.15 Peterborough Bridge 184 ............................................................................................ 10

3.16 Lock Lane Long Eaton, Bridge 3 ................................................................................. 10

3.17 Kentish Town PACT (Paved Concrete Track) System Transitions .............................. 11

3.18 Manningtree North Junction ........................................................................................ 11

3.19 Grove Hill Tunnel, Tunbridge Wells............................................................................. 11

3.20 Syston North Junction ................................................................................................. 12

3.21 Knighton Junction ....................................................................................................... 12

3.22 Keadby Bridge Abutment Reconstruction.................................................................... 12

3.23 Balavil Burn and Gynack Burn .................................................................................... 13

3.24 Falkirk Tunnel PACT System Transitions .................................................................... 13

3.25 Tottenham South Junction .......................................................................................... 13

3.26 Purfleet Deep Wharf Level Crossing ........................................................................... 14

3.27 Bletchley ..................................................................................................................... 14

3.28 Worplesdon Hop Garden ............................................................................................ 14

3.29 Norwich – Ely .............................................................................................................. 15

3.30 WCML Bridge Resonance Programme ....................................................................... 15

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Introduction 1

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

The polymer is applied in-situ by mixing two chemical components through a mixing lance. The polymer is poured on to and penetrates into the track ballast. The polymer typically cures within 10 to 15 seconds. It achieves 50% of its designed strength within minutes and reaches 90% of its strength 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. The benefit 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 the polymer make it an ideal material for railway environments where operating conditions can result in sudden 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 is still maintained.

Bonding of the polymer to the ballast will occur but this is not critical, as the primary function of the treatment is to generate polymer-reinforcing elements at every level in the ballast matrix, both vertically and horizontally, essentially encapsulating the ballast. Bonding of the polymer, to the ballast, is not therefore required for the technique to work, which is the fundamental difference with ballast 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 designed tolerances and reduce maintenance intervention. The design philosophy considers three separate components, lateral and vertical restraint and ballast settlement.

Compressive Strength of Ballast Tensile Strength of Polymer Inherent Geocomposite Strength

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1.1 Lateral Restraint

The XiTRACK system as a solution to maintain lateral alignment is well proven. It has had multiple applications in similar scenarios to provide restraint on curves, at platforms and through switch and crossing units.

1.2 Vertical Alignment

The 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 the intention in this application to provide track restraint and manage track bed stiffness.

1.3 Minimise Ballast Settlement

Settlement in ballast is well documented. The XiTRACK treated ballast will not consolidate under traffic, unlike ballast which is left untreated. Any loss of top or development of twist faults or risk of differential settlement of the superstructure is therefore minimised. In principle the XiTRACK treated 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 occur immediately after application of the polymer as it sets in seconds. Under normal conditions XiTRACK can be loaded by site traffic, including vibro-plates, 15 minutes after polymer application and by rolling stock 30 minutes after polymer application.

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

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

• Scheme Cost Benefits. XiTRACK is a value engineered solution that will produce life cycle cost benefits. Savings are possible through much reduced compensation payments to Train Operating Companies and Freight Operating Companies as a direct result of its very rapid installation and curing time leading to smaller blockades and disruptive possessions. In addition as it is an engineered ‘solution’ to recurring defects it will help reduce spend on future maintenance.

• Can be applied at any time of the year.

• Is designed for the particular project and user requirements.

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Applications 2

XiTRACK has a range of designed applications:

• Transitions to and from ballasted track to other track-forms such as slab track and bridge structures.

• Increasing vertical stiffness of track to reduce or eliminate maintenance problems, or allow an increase 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 installations

There are broadly two sets of criteria which can be used to make a judgement on the attractiveness of the XiTRACK solution; these are:

• Financial Analysis of the known facts and figures for the asset. This leads to an objective view of 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 engineering management.

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 can be 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 been arrived at across the full range of job types. The projects described in this paper have all been subjected to a business case development by the client

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Installations 3

3.1 Toadmoor Tunnel

As part of the Midland Mainline Line Speed improvement Project the line speed through Toadmoor Tunnel was increased from 60 to 80mph. Toadmoor has historically been a difficult site to maintain and it was feared a speed increase would make it more so. XiTRACK was used to create a low maintenance high fixity track form was installed in the tunnel. The installation was undertaken in non-disruptive possessions.

3.2 Canal Tunnels

The XiTRACK design was required to provide stabilisation to cater for anticipated ground movement at the Canal Tunnels Sonneville slabtrack to ballast interface. Whilst also providing lateral fixity to maintain track alignment at this critical area.

The complex track geometry and location next to the concrete slabtrack transition made it particularly desirable to mitigate track maintenance input as far as practicable.

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3.3 Whiley Hill Masonry Arch Bridge XiSPAN Trial

Network Rail owns and maintains the oldest masonry arch railway bridges in the world. Many are beyond their design life and are suffering the effects of aging which is increasing the ongoing maintenance burden.

Balfour Beatty Rail and a team of industry experts worked with Network Rail to develop an innovative, cost effective strengthening solution to prolong the life of these critical assets and preserve their historical legacy.

Balfour Beatty Rail worked with Network Rail to identify a suitable structure to trial a polymer based solution on. The bridge in question is at Whiley Hill on the Stockton and Darlington line. Built by George Stephenson in 1824, it is possibly 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 geocomposite raft comprising of ballast and advanced polyurethane, positioned between the track and bridge would address these objectives.

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3.4 University Station, MTR, Hong Kong

XiTRACK was successfully installed between the sleeper end and the platform wall to provide lateral resistance to track movement.

In-situ testing on a test installation at Fo Tan depot showed displacements of 0.9mm for 100kN sleeper end load.

This installation was completed June 2012. Monitoring to May 2014, has showed a maximum sleeper displacement of 3mm at University station.

3.5 Famagosta-Assago, Milan Metro, Italy

A new extension to the Milan Metro incorporated a concrete slab track underbridge abutting conventional ballasted track. XiTRACK was used to combat voiding at the interface. The installation took the form of a ladder structure with edge beams, locking the ballasted track in position and controlling track settlement, resulting in a reduced potential for voiding at the site. The XiTRACK installation was completed in November 2010.

3.6 Dalston West Curve transition, East London Line

XiTRACK ballast reinforcement was used to reduce the occurrence of voiding at the interface between concrete slab track and ballasted track. The treated section comprised a ‘ladder type’ XiTRACK structure adjacent to the slab track to reduce voids and dynamic deflection of the ballasted track. Edge beams were also installed to give increased lateral resistance to the ballasted track to ensure horizontal alignment of the ballasted track with the slab track. These were installed over a longer length than the ladder structure, extending the reinforcement to a vehicle track crossing. The XiTRACK installation was

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

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3.7 Dalston West Curve Sewer, East London Line

A Victorian cast iron sewer runs under the East London Line at a very shallow depth beneath the track. XiTRACK was used here in April 2010 to transition the track formation over the sewer. The XiTRACK design protects the sewer and prevents the creation of track maintenance problems.

3.8 Gravel Hole, West Coast Main Line (Up Line)

A section of the West Coast Main Line in Lancashire runs over an area of very poor ground which had lead to the long-term imposition of a temporary speed restriction. The soft ground lead to critical track velocity and Rayleigh wave induced track maintenance problems

XiTRACK formation improvement works were undertaken in March 2010 with sub-ballast reinforcement provided by the XiTRACK system. Before and after Falling Weight Deflectometer measurements were taken in order to assess whether to reopen the line at 125mph line speed. Measurements confirmed that the XiTRACK treated track was working as designed and the line speed was lifted to 125mph.

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3.9 River Lea Under-bridge, North London Line

This site was historically a maintenance problem due to a sudden track stiffness change between this bridge and the adjacent embankment. XiTRACK was used to create a constant rate of change of stiffness between the bridge and the embankment.

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

3.10 East London Line Extension

Extensive XiTRACK work was undertaken on the East London Line in August 2009. The work included vertical track reinforcement on the Surrey Canal Road Line and on the New Cross Flyover and increasing track fixity through stations.

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

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

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3.11 Kavanaghs Road Bridge Transitions, Brentwood

In order to help prevent voiding at the interface between a longitudinal timber bridge and plain-line track, XiTRACK ballast reinforcement was used in a ‘ladder type’ structure near the bridge/ballast interface. The purpose of this treatment was to reduce voids close to the bridge through 3-dimensional ballast reinforcement and to provide a graduated ballast stiffness (within the geocomposite) to help reduce track deflection from the ballast dynamic response.

The XiTRACK installation was carried out in order to help reduce future track maintenance requirements by reinforcing and strengthening the ballast and giving transitional track stiffness characteristics. Work was completed in July 2009.

3.12 Clapham Junction, Windsor Ladder

Clapham junction is one of the busiest railway junctions in the world. Because of this, access for inspection, maintenance and repair is very limited. XiTRACK was chosen at this location to increase the Reliability, Availability, Maintainability (“RAMS”) requirements of the Windsor Ladder.

3.13 Bletchley Fixed Diamond

Following on from the continuous satisfactory performance of XiTRACK that was installed at some Switches and Crossings several years earlier, the Track Maintenance Engineer utilised XiTRACK to address voiding problems beneath a fixed diamond that had lead to a speed restriction and increased maintenance intervention. A pad was constructed to give uniform stiffness to a layer of ballast beneath the bottom ballast enabling tamping activities to be unaffected.

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

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3.14 Newham Bog

Here the East Coast Main Line rail route north of Newcastle runs across a section of very poor ground. A long history of problems had been encountered at the interface with a boulder clay formation and a line speed reduction was necessary owing to the low Critical Track Velocity at the site. XiTRACK Polyurethane Ballast Reinforcement was used to stiffen up the formation to provide a graded change from the boulder clay to the soft peat bog, replacing geocells which were installed in the 1980’s.

3.15 Peterborough Bridge 184

XiTRACK was specified as part of the plain line track renewal works as a means of managing track stiffness at the interface with a longitudinal timber bridge. XiTRACK was applied to the bottom ballast with the track in-situ as a means of preventing future track quality problems and voiding.

3.16 Lock Lane Long Eaton, Bridge 3

This was a maintenance scheme to prevent the return of ongoing track quality issues at this location. Along with the renewal of the longitudinal timbers on the bridge, XiTRACK was applied on the approaches and run offs with the existing track in-situ to prevent track voiding at the interface with the structure.

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3.17 Kentish Town PACT (Paved Concrete Track) System Transitions

At this location the existing concrete transition structures between the slab and ballasted track were beginning to fail and proving to be a maintenance problem. They were replaced with a XiTRACK design that enabled ordinary track components to be used right up to the interface with the slab thus considerably reducing the maintenance burden.

A design, project management and installation scheme was carried out successfully during the associated plain line track renewal.

3.18 Manningtree North Junction

Here the change in track stiffness from a structure to an embankment and then to an under bridge was causing track quality problems, particularly at the interface with Switches and Crossings at the junction. During the junction’s renewal the opportunity was taken to install a layer of XiTRACK sub ballast with a varying stiffness, designed to grade out the hard spots caused by the structures.

3.19 Grove Hill Tunnel, Tunbridge Wells

This major construction scheme saw the replacement of approximately 120m of failed slab track system which had originally been installed to maintain tight clearances through the tunnel but had failed owing to drainage issues. A bed of free draining XiTRACK treated ballast was used instead with a collector drain running along the centre. The track was laid on this and the clearances maintained by means of XiTRACK edge restraint beams.

This scheme has solved the drainage issues originally present on site and continues to perform well.

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3.20 Syston North Junction

Here lateral track stability problems are aggravated by the tight radius of the turnout which, although the line speed is relatively low, does lead to significant lateral forces.

End restraint plates had been used but failed to maintain the alignment and so an alternative was sought.

XiTRACK application was completed within schedule and subsequent monitoring has confirmed that the treated areas have performed as expected.

3.21 Knighton Junction

XiTRACK treatment was designed to give a polymer loading leading to a maintainable, improved alternative to end-plates for improving the lateral stability of the junction.

XiTRACK polymer application was completed within schedule and subsequent track recording train runs show the alignment to be satisfactorily retained.

3.22 Keadby Bridge Abutment Reconstruction

Keadby was another major construction scheme where XiTRACK was utilised. The bridge was replaced in 2003 and since construction there had been alignment problems due to movements within the abutments and substructure arising from train loading and bridge movements. During the planned renewal of the abutments during a blockade over Christmas 2006, XiTRACK treatment was applied to produce geocomposite reinforcement of the transitions on both the East and West abutments at this important structure.

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3.23 Balavil Burn and Gynack Burn

Two bridges on the Highland Main Line at Gynack and Balavil near Kingussie are prone to flooding causing heavy ballast contamination and potential wash-out, leading to track defects, disruption and subsequent delays.

A XiTRACK scheme was devised for each of the bridge transitions to help prevent ballast being washed out under the sleepers during such periods of flooding. This gives protection to the ballast under the sleepers permitting any water to pass through the geocomposite but allows all forms of conventional maintenance to occur.

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

3.24 Falkirk Tunnel PACT System Transitions

In order to reduce the dynamic load on the run-on to the concrete slab-track, a stiffened transition was necessary. It was known that the concrete track transition structure had deteriorated and in addition the site suffered from water ingress problems and the XiTRACK design had to accommodate these effects.

A suitable XiTRACK design was installed and performs as expected.

3.25 Tottenham South Junction

A complex scheme of vertical and lateral XiTRACK reinforcement of the transition area was designed to improve the performance under local heavy passenger and freight loading and particular attention was paid to the ballast on the bridge deck itself near to the toes of the Switches and Crossings.

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3.26 Purfleet Deep Wharf Level Crossing

The level crossing was showing signs of bearing failure, pocketing and rutting due to the weak formation and the very soft Alluvium clays known to exist in the sub grade. In view of the current and anticipated future loading conditions, along with needing to minimise line closure time, a XiTRACK treatment was considered desirable in order to provide a long-term cost effective solution.

A XiTRACK design was prepared for the site and polymer applied in the specified loading pattern and, including all groundworks, the site was returned to full rail and road traffic after a total closure time of only three days.

3.27 Bletchley

Switches and Crossings at Bletchley were treated to correct vertical and lateral stability problems on this high-speed section of the West Coast Main Line. The site had been a major maintenance headache for some time with imposed speed restrictions until XiTRACK was applied.

This site continues to perform and led to additional schemes being implemented in the surrounding area.

3.28 Worplesdon Hop Garden

The XiTRACK technique was used to reinforce and stabilise the vertical bridge transitions for the Hop Garden Bridge on the Up Guildford line near Worplesdon Station. XiTRACK was used to stabilise the transition in its current configuration to help prevent further deterioration of the track geometry. The site was treated to allow full maintenance if required using manual techniques.

No vertical re-alignment has been required since treatment.

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3.29 Norwich – Ely

XiTRACK treatment removed the persistent lateral track faults around these transitions where tamping is difficult or impossible and no lateral re-alignment has been needed since the application.

The treatment area was adjacent to a river and all requirements of the Environmental Agency were met.

3.30 WCML Bridge Resonance Programme

XiTRACK Polymer was applied to ballast on a series of bridges on the West Coast Main Line in Network Rail’s Test Site A, in the Trent Valley and in Scotland.

The bridges in the series were usually based on a steel plate decking and had been found to be subject to pre-resonance problems at normal passenger train speed. They had been shown to be susceptible to ballast movement due to induced excitement with consequent loss of track alignment. This problem had been demonstrated to be likely to get worse with Pendolino increased line speeds.

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

Contact Details

Dermot Kelly Balfour Beatty Rail Ltd Fitology House Smedley Street East Matlock Derbyshire DE4 3GH Telephone: +44 (0)1629 761 441 Mobile: +44 (0)7967 668 929 Fax: +44 (0)1629 760 751 Email: Dermot.Kelly@bbrail.com Matt Hunt Balfour Beatty Rail Ltd Fitology House Smedley Street East Matlock Derbyshire DE4 3GH Telephone: +44 (0)1629 761 449 Mobile: +44 (0)7765 407 695 Fax: +44 (0)1629 760 751 Email: Matt.Hunt2@bbrail.com

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