Ted Sussmann VOLPE and Hugh Thompson FRA

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Canadian TSB Investigation: Subgrade Settlement. • Led to NRC ... settlement and associated track geometry deviation development. 4. ... Joint bar overload.
Ted Sussmann VOLPE and Hugh Thompson FRA

FRA TSS § 213.103 Ballast: Unless it is otherwise structurally supported, all track shall be supported by material which will— (a) Transmit and distribute the load of the track and railroad rolling equipment to the subgrade; (b) Restrain the track laterally, longitudinally, and vertically under dynamic loads imposed by railroad rolling equipment and thermal stress exerted by the rails; (c) Provide adequate drainage for the track; and (d) Maintain proper track crosslevel, surface, and alignment.

Assumption: ballast support needed for geometric stability until next inspection 2

Photo: T. R. Sussmann

• Vertical Track Deflection is often related to the performance of the track. – Small deflections (0.10 inches) indicate stiff track with a slow degradation rates – Large deflections (0.50 inches or greater) indicate soft track with generally higher degradation rates

Source: W. W. Hay, Railroad Engineering, 1982



Cox Landing, WV June 1998 (with Haz Mat Release) – NTSB Investigation: Unstable roadbed, Drainage •



Result: University of Nebraska Track Deflection Research

Westminster, VT April 2001 – Slope instability, salt train derailment •



Site assessment spurred interest in quantitative tools to assess track support

Canada Track Failure 2004 – Canadian TSB Investigation: Subgrade Settlement •



Led to NRC research on track deflection

3x- Powder River Basin, May 2005 – Blocked access to coal for energy producers (U.S. DOE Study) •

Surface Transportation Board: Coal Fouled Ballast

– Sparked interest in ballast fouling condition • Ground Penetrating Radar for coal dust

• Ellicott City, MD August 2012 (2 fatalities) – NTSB: Broken Rail with evidence of rail overstress – Vertical Track Deflection Report to Congress

Substructure Track Support Risks 1. Track Loads Vehicle applied track loads beyond design safety factored loads may cause deformation beyond that assumed in design that would reduce the useful life of the track substructure and result overloading track superstructure components.

2. CWR Stability Rail internal forces must be controlled and properly reacted to prevent buckling or track shift related alignment deviations.

3. Fouled Ballast Ballast must provide resilient support with minimal plastic deformation to limit track settlement and associated track geometry deviation development.

4. Subgrade Stability Subgrade must serve as a stable platform contributing to the stability and resilience of the entire track structure.

Track Support Proper track support (particularly 3 and 4) is required to assure rail infrastructure resilience.

• Track Support: key to analysis of track load capacity limitations and occurrence of critical stress/strain – Lateral: Buckling analysis. CWR Maintenance. Potential for better understanding the shift and buckling breakpoint. – Vertical: Poor support track failure, geometry deterioration. – Longitudinal: Rail stress, rail running, neutral temperature.

Figures adapted from Selig and Waters, Railway Geotechnology, 1994

Too stiff:  Rail corrugation  Tie abrasion  Ballast crushing Crushed railhead Load

Too soft:

Void

Contact Deflection

Figure adapted from Sussmann et al., Fundamental Track Load Deflection Behavior, TRB, 2001.

 Ballast instability  Subgrade failure  Joint bar overload

Photo courtesy Mike Coltman.

Large void:  Track shift/buckling  Track geometry  Tie failure  Fouled ballast Photo: T. R. Sussmann

Track Support Problems • Track Load Redistribution • Ballast Rearrangement • Track Geometry

Figure courtesy Mario Ruel, CN

Inspection: GPR (Ground Penetrating Radar) • Clean Ballast Depth, Moisture • Longitudinal Variations

Tie Bearing Capacity Problems • Tie and Rail Loads • Cross Level and Geometry • Track Position Movement

Figure courtesy FRA

Inspection: Seismic (SASW) • Resilient Modulus • Density

Squeeze/Heave

Ballast Pockets

Li et al., Railway Geotechnics, 2017

Photo: T. R. Sussmann

Photo: T. R. Sussmann

Inspection/Quality Control: Strength from Modulus Correlation

• FRA DOTX 218 Track Deflection System Installation

Photo courtesy John Choros, Volpe (ret.).

Photo courtesy Ensco, Inc.

Rough

Smooth

Rough

Smooth

Figures and photos from Stark et. al (2015): Evaluation of Tie Support, TRB, DOI: 10.3141/2476-08

0.01 in.

Tie-Ballast Gap

0.25 in.

Figures and photos from Stark et. al (2015): Evaluation of Tie Support, TRB, DOI: 10.3141/2476-08

VTD System Overview Uniform track with no geometry variations Deflection of track 4 feet aw ay from w heel

𝑌𝑌𝑟𝑟𝑟𝑟𝑟𝑟 = 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝐸𝐸𝐸𝐸𝐸𝐸 = 0 𝑉𝑉𝑉𝑉𝑉𝑉 ≈ 𝑌𝑌𝑅𝑅𝑅𝑅𝑅𝑅 − 𝐸𝐸𝐸𝐸𝐸𝐸

Unloaded track position

𝐻𝐻𝐿𝐿

Loaded spacecurve (w heel path)

yrel

𝑌𝑌𝑟𝑟𝑟𝑟𝑟𝑟 - references partially loaded rail position at 4 feet away from wheel

𝐸𝐸𝐸𝐸𝐸𝐸 - End Chord Offset references a loaded spacecurve calculated from track geometry measurements 𝑉𝑉𝑉𝑉𝑉𝑉 – Vertical Track Deflection is approximated by subtracting 𝑌𝑌𝑟𝑟𝑟𝑟𝑟𝑟 and 𝐸𝐸𝐸𝐸𝐸𝐸. Figure adaptation by Gary Carr, FRA.

VTD System Overview

𝒀𝒀𝒓𝒓𝒓𝒓𝒓𝒓 measurement with track geometry variations 𝐻𝐻𝐿𝐿 Loaded spacecurve (w heel path)

Unloaded track position

𝑉𝑉𝑉𝑉𝑉𝑉 ≈ 𝑌𝑌𝑅𝑅𝑅𝑅𝑅𝑅 − 𝐸𝐸𝐸𝐸𝐸𝐸

yrel ECO

𝐻𝐻𝐿𝐿 - Laser height measurement from UNL beam to top of rail Figure adaptation by Gary Carr, FRA.

Failure or rapid deterioration of track superstructure North Deflection (in.)

South Deflection (in.)

Failure or rapid deterioration of track superstructure

Six (6) failed concrete ties in a row - track immediately taken out of service Photos: T. R. Sussmann

Unrestrained track or rail due to settlement North Deflection (in.)

South Deflection (in.)

Unrestrained track or rail due to settlement

• Insulated joint with apparent signs of distress including loose huck bolt, which is not common • Spike lifted 3-4 in. at joint • Track deflection appears about ¾ in. of slack based on gap at bottom of tie. Photos: T. R. Sussmann

Goal: Foundation failure

- Settlement: 30 cm over 8 years - Failure due to sudden and significant settlement - Spurred Canadian research into VTD

Figures: Canadian Transportation Safety Board Railway Investigation Report: R04Q0040, 2004

• Track support is a critical element of a reliable transportation network – Poor track support  slow orders and unpredictable maintenance

• Track deflection measurement is a challenge, but examples are emerging that demonstrate the criticality of track structural performance • Track settlement effects such as hanging ties and rail contribute to track deflection and dynamic load