Acton Diveunder – West of England section PWI presentation – 25th March 2020
Acton Diveunder (and Yard)
Part of the works to support the Network Rail Crossrail On-Network works
Presentation to West of England PWI section, 25th March 2020 Philip Holbourn, Track Engineer, Holbourn Engineering Ltd
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Me: Philip Holbourn
Then: Project Engineer (Track), Acton Diveunder, Sept 2013 until May 2016
Currently: Senior Project Engineer (Track), South Wales Electrification
Also: Part-time lecturer, Coventry University, Sept 2007 to present day
Previously: Project Engineer (Track) & DPE, Crossrail ONW West Outer – Track Lowering, August 2010 until September 2013
Track Design Engineer, Scott Wilson Railways, Birmingham September 2003 until August 2010
[email protected] https://www.linkedin.com/in/philip-holbourn-6577812b/
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Acton Diveunder (and Yard)
Things I’ll cover:
The project itself Design of the slab track Design of the transitions Other linked elements Construction of the diveunder structure Construction of the Slab track Some interesting issues along the journey…
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Acton yard: Final Layout
Diveunder is a diversionary route. No timetabled services initially. To be used to avoid train delays due to conflicts between Up Relief passenger trains and freight traffic entering and leaving Acton Yard.
Acton freight yard
--> NLL (Acton Wells Jn) Diveunder Diveunder
--> London Pad
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Before and After
75mph
90mph
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Site congestion / Access
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Site congestion / Access / Features
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Plenty of room to work in…
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Write the buffer stop risk assessment…
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Marjorie!
/ 10 Acton Diveunder – West of England section PWI presentation – 25th March 2020 East headshunt buffer – ‘Easy’ early job.
But history got in the way…
/ 11 11 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Entrance Alignment
Horizontal Radius (m) E (mm) Length (m) Vertical -2797 0 118 Element Length (m) Value Trans 50 Grade 205 1 in 1471 down -5000 -25 88 Trans 60 VC 82 3400m ⌢ 5000 25 62 Grade 172 1 in 40 down Trans 30 VC 161 3600m ⌣ 0 0 158
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Exit Alignment
Horizontal Vertical Radius (m) E (mm) Length (m) Element Length (m) Value 0 0 158 VC 161 3600m ⌣ Trans 60 Grade 239 1 in 50 up -2500 -60 63 VC 72 3400m ⌢ Trans 30 -4125 -40 272 Grade 87 1 in 787 up
/ 13 Acton Diveunder – West of England section PWI presentation – 25th March 2020 The Acton Roller Coaster!
/ 14 Acton Diveunder – West of England section PWI presentation – 25th March 2020 The Acton Roller Coaster!
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Ballasted vs Slab Track
► Geometry • 90mph, 75mph for exit S&C. • 1:40 down, 3600m 4.58%g VC, 1:50 up • Horizontal reverse curves, some RoCD near maximum. • Horizontal transitions coincident with vertical curves - → High track accuracy and high track fixity required!
► Construction depth • Deep ballast required • Concrete → Shallower → Less dig
► Ballast degradation • High forces → High ballast attrition on concrete base
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Issues Assessed for Slab Track Constructability
► Top down vs. bottom up construction – accuracy of different sections.
► Braking/creep/thermal force resistance and load distribution
► Installation methods
Maintainability Systems Considered ► Type of fastening – Vossloh vs. fastclip. ► Embedded Rail
► Welding & managing defects – Ref HeX tunnels… ► Resilient Baseplate ► Booted Sleeper ► Settlement of transition zones ► Cast-in Sleeper ► Floating Slab Performance
► Rail creep
► Rail wear and RCF susceptibility
► Pad stiffness over time
► Signal in diveunder on 1 in 50 gradient
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Rheda 2000 (standard configuration)
/ 18 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Rheda 2000 – Extreme Gradient
/ 19 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Slab Track System - Key points Constructability • 1:40 down and 1:50 up • Construction accuracy: - +/- 2mm. Maintainability • Rheda system with Vossloh 300 fastenings used in Paddington station • 70mm clearance bottom of rail → top of slab • Fastenings can be replaced easily in case of failure. Track Slab → Base slab integrity • Dowels provided between slabs Drainage system – Water flow path • Fall on top of slab will ensure water falls to side gullies and not run along the 4ft.
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Form B - Typical cross sections at depth
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The Diveunder : Separate structures
► Slabtrack length: 730m 1. Track Transition ballasted box 2. 99m RC Trough - raft 3. 475m Base slab - piled 4. 156m RC Trough - raft 5. Track Transition ballasted box
/ 22 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Some interesting features
/ 23 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Some interesting features
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Transition Slabs – NR Draft Standard (June 2014)
NR Draft Standard - The Investigation, Design and Installation of Trackbed NR/L2/TRK/4239
/ 25 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Slab→ Ballast transition design
► Transition steps: 1. Slab track 2. Ballasted trough with ballast mat 3. Ballasted trough with stiffer ballast mat 4. Granular wedge
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R=4125m E=40mm V=90mph
/ 27 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Slab→ Ballast transition design
► Slab → 300mm ballast depth immediately
► Ballast containment: Trough widens from 3.3 to 3.9m wide
/ 28 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Slab→ Ballast transition design
► Draft NR standard partially used
► German philosophy for transitions partially used
► Basics of graduated stiffness change followed
► Granular fill and shear connectors included
/ 29 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Slab→ Ballast transition design
► Transition is into soft London clay
► Sand blanket and Class 1A fill layers
/ 30 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Drainage of Transitions
► Granular wedge drainage – Important!
► Ballasted trough has pipes out
/ 31 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Drainage in Diveunder Gully pots along both sides
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Diveunder Drainage
- Gullies every 6.5m on both sides - 225mm diam collector pipes, multiple inspection chambers - 600mm diam outlet to pumping station - Duty / assist / standby pumps capacity 20l/s - No flooding in 1:50 year storm - Rising main connected direct to public sewer
/ 33 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Drainage from Diveunder Attenuation and pumps required
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7.5m diameter 9.5m deep 2.1m thick concrete base below 2m from base of DU to base of tank
/ 35 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Track-Ex modelling
Track-Ex modelling undertaken: • Criteria deliberately exaggerated to produce a worst-case scenario. • But: Track-Ex does not take account of vertical geometry.
Results: • Negligible RCF and wear in the diveunder. • Light RCF is expected in the S&C at the East end, requiring grinding assessment after approx. 6-8 years.
MLN1 1201 [0mi - 0yd] Acton Dive Under5 MLN1 1201 [0mi - 1347yd] 1.20 1.00 0.80 0.60 0.40 0.20 0.00 0 200 400 600 800 1000 1200
Light RCF-NDN GDIdy_HiToR-1_260_NoLube_UnGround_52Wks_C4X5S6L9G10 17-17-23-NDM Distance-metre
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Finite Element modelling
FE Modelling undertaken to validate transition design.
Used a Finite Element Dynamic Model developed by the University of Birmingham. Model used via the Network Rail Trackbed Investigation Team in Birmingham.
/ 37 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Form B approval
► Significant work to validate choice of system and design of transitions
► Technical reports produced
► Very detailed Form B produced with extra signature boxes
► ‘Collaborative Cat III check’ undertaken
► PHoT approval obtained
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Diveunder Piles and Base Slab
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Base slab
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Work in progress - Centre
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Work in progress – East end
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Diveunder Intersection Bridge
/ 43 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Setting out & preparing alignment
/ 44 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Preparing for concrete pouring
/ 45 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Pouring
/ 46 Acton Diveunder – West of England section PWI presentation – 25th March 2020 Almost there! Stressing: • PP location • Rollers
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Some interesting track layouts - Installed
A new double slip, which is a major part of the layout at the West end.
All traffic that uses the West headshunt has to use this.
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Some interesting track layouts - Installed
A new tandem Note the amount of S&C that is also connects to. The next set off the toes is the new double slip
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Some interesting track layouts - Installed
Part of Acton West Jn: G crossover plus F turnout with shared bearers including double bearer splices
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Some interesting track layouts - Installed
H switch – The biggest you can get! 90mph on both main and turnout routes, for entry into the Diveunder
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A few other interesting track issues… Drainage before track – quality issues with backfill! Lots of rails – Disruption to yard operations
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A few other interesting track issues… Significant lipping of plain Guess the line (on 250m radius) and an adjustment switch age! (straight) plus significant degradation of a crossing 5 months! (1 in 10.75 welded vee)
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A few other interesting track issues… NR60E switch 053 failures Age = 7 months. Installation was Christmas 2013. Photos taken July 2014. Heavy trailing direction freight moves. Known design issue at REPW level. Guess the age!
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Christmas 2013 works – Issues & Solutions
►Power cable to diveunder pump accidentally severed but not noticed!
► Wetsuit team rescued equipment and re-started pumps
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Yard - Operational safety
►Bollards!
► Reception 1 is 25mph with trains normally signalled. Rest of yard is 15mph on PLs. These are to provide a visual reminder of the hazard.
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Christmas 2013 works – General features
►Outer guard rail arrangement around TPWS grids
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Ground Frames modernised
►This is the Local Control Unit – a little better than a ground frame…
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Christmas 2013 works – Finished article
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Any questions?
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