Ballast Thickness Design for Changing Environment(s)
Transcript of Ballast Thickness Design for Changing Environment(s)
![Page 1: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/1.jpg)
Ballast Thickness Design for Changing Environment(s)
Ted Sussmann
Civil, Environmental, and Biomedical EngineeringCollege of Engineering Technology and Architecture
SEPTEMBER 17, 2021
![Page 2: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/2.jpg)
Track
“A common corrective for poor trackhas been to lay new and heavierrail. The money might often bebetter spent in increasing thestrength and stiffness of the railsupport. One might as well try tostabilize a sinking building byadding another story to it.”
William W. Hay (1982)
2
Source: Li et al, 2015System
{
![Page 3: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/3.jpg)
Ideal TrackAn Ideal Roadbed“Disregarding for the present the matter of initial cost, Iet us briefly consider the requirements for a roadbed that is ideal:First: the load must be distributed over a large area of the subgrade.Second: the rail must have continuous support.Third: Economical means for adjusting the surface must be provided.”
“What is an ldeal Roadbed worth to the Railroad?”Paul Chipman (1930)Engineers Club of Philadephia
3
Source: Chipman, 1930
![Page 4: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/4.jpg)
OutlineTrack Design Concept and PhilosophyRisks Affecting Track StructureChanging Environment(s)Opportunities to Apply Design PhilosophySummary
![Page 5: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/5.jpg)
Track Design Concept And Philosophy
![Page 6: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/6.jpg)
Track Design Concept
• Track Cross Section– Ballast – Subballast– Subgrade
• Design Thickness and Profile– Thickness for adequate load resistance– Profile for drainage
6
Source: Li et al, 2015
![Page 7: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/7.jpg)
Load DistributionStation / Water Treatment
Plant (Weston and Sampson)
• Load Distribution:– Rail load to group of ties– Ties load to ballast
• Load distribution along the track and along ties affected by track support
– Stiff track support with little rail deflection concentrates load on tie most directly below wheel load
– Soft track support increases rail deflection engaging larger group of ties
7
Source: Selig and Waters, 1994
![Page 8: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/8.jpg)
Load DistributionStation / Water Treatment
Plant (Weston and Sampson)
• Comparison of concrete and wood tie load distribution (GeoTrack)
– Concrete tie track stiffer distributing load along tie– 10 psi contour to same depth but shape different– Wood tie distributes higher tie load to ballast at
approximately same pressure
• Model Details– Ballast
• 18 in. thick, 60 ksi modulus
– Subgrade• 8 ksi modulus
8
![Page 9: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/9.jpg)
Track Design PhilosophyStation / Water Treatment
Plant (Weston and Sampson)Develop track cross section to:• Distribute applied loads to subgrade at
acceptable level by• Protecting the layer below and• Providing resilient support to the tie,• Limiting plastic deformation and
settlement
9
![Page 10: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/10.jpg)
Ballast Design CriteriaStation / Water Treatment
Plant (Weston and Sampson)Excessive Plastic Strain• Subgrade Squeeze
Excessive Plastic Deformation• Ballast Pockets
10
Subgrade Squeeze
Ballast Pockets
![Page 11: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/11.jpg)
Design MethodStation / Water Treatment
Plant (Weston and Sampson)Ballast Thickness Required for Subgrade Properties• Based on Track Life / Number of Load Cycles (N)• Design Wheel Load (Pd)Considering• ρa = allowable subgrade deformation• Subgrade soil type• Subgrade and Ballast Moduli• Subgrade strength• T: Subgrade thickness• L: 6 in. Constant
11
Source: Li et al, 2015
![Page 12: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/12.jpg)
Design Method part bStation / Water Treatment
Plant (Weston and Sampson)
12
Source: Li et al, 2015
Soil Type a b m
CH (fat clay) 1.2 0.18 2.4
CL (lean clay) 1.1 0.16 2.0
MH (elastic silt) 0.84 0.13 2.0
ML (silt) 0.64 0.10 1.7
![Page 13: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/13.jpg)
Validating Design / Evaluating Performance Station / Water Treatment Plant
(Weston and Sampson)Same Equation: Track Life in Number of Load CyclesConsidering• Ballast Thickness and Properties• Subgrade Thickness and Properties• Design Wheel LoadConsidering• ρa = allowable subgrade deformation• Soil Properties based on soil type (a, b, m)• A & L constants
13
Source: Figure: Li et al, 2015Data: O’Riordan and Phear (2001)
![Page 14: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/14.jpg)
Risks Affecting the Track Structure
![Page 15: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/15.jpg)
Overload• Loads exceed available resistance• Vertical
– Tie Ballast Interface– Subgrade
• Lateral– Misalignment– Tie end-ballast gap
• Longitudinal– Tie Cavity
15
![Page 16: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/16.jpg)
Environment• Heat
– Buckling
• Cold– Pull apart
• Heavy Rain– Saturation
• Flooding– Washout– Embankment failure with rapid drawdown
• Dry/Arid– Sand/dust blow into ballast/cover tracks
16
Source: Library of Congress
![Page 17: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/17.jpg)
Drainage
• Local Effects– Abrasion– Ballast Pockets– Subgrade Squeeze– Ballast Fouling/Mud Pumping
• Global Effects– Track Structure Deterioration– Track Geometry– Layer Intermixing– Embankment Stability
17
Source: Hay Lecture by Gary Wolf
Short
Long
![Page 18: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/18.jpg)
Dynamic Pore Water Pressure
18
![Page 19: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/19.jpg)
Principal Stress Rotation
• Factor in dynamic pore water pressure development
• Shear stress reversal affects track life predictions
19
![Page 20: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/20.jpg)
Changing Environment
![Page 21: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/21.jpg)
Environmental Changes
• Severe precipitation events present risks that vary locally
• Railroads first infrastructure after water based transportation (canals)– Many lines follow rivers and canals– Railroads tend to be some of the
lowest elevation infrastructure
• Preserving lifelines will require improved knowledge of local factors
21
![Page 22: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/22.jpg)
Operations
Factors• Wheel Load • Train Length/Speed/Headway• Train Makeup/Load Distribution• Coupler Length/Axle Spacing• Precision Scheduled RailroadingEffects• Load and Traffic affect design life• Axle Spacing/Coupler Length
affect load cycle count• PSR affects impact of delays due
to unplanned maintenance
22
Source: Figure: Li et al, 2015Data: AAR, 2012
![Page 23: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/23.jpg)
Maintenance
• Historic– Large Track Gangs– Section Personnel
• Current– Division Mechanized Gangs– Division Personnel
• Future– Internet of Things: IoT– Fourth Industrial Revolution: RR4.0
23
Source: Library of Congress
Source: Li et al, 2015
?
![Page 24: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/24.jpg)
Right of Way
• Historic– Large number of track miles– Alternative Routes
• Current– Rationalized Route Miles– Concentrated Traffic on Main Routes
• Future– Dedicated corridors for select traffic– Combined corridors for highway, rail,
pipeline, data…
24
Source: Library of Congress
![Page 25: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/25.jpg)
Past Right of Way
25
1853 Connecticut Infrastructure: Rail2016 Connecticut Rail Map
Source: CT DOT and Library of Congress
![Page 26: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/26.jpg)
Future Right of Way
• 1850– Canal– Train – Trolley
• 1950– Train– Automobile & Truck
• 2050– Driverless Auto– Hyperloop– …
• …
26
Source: Nasa
Predictable Rail Freight, Transit…Train
![Page 27: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/27.jpg)
Opportunities to Apply Design Philosophy
![Page 28: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/28.jpg)
Opportunities: Address Risks
• Natural / Environmental Hazards– Drainage– Hardening Embankments Against Erosion– Floodplain Design
• Local GeoHazard– Subgrade Performance– Ballast Performance
• Global GeoHazard– Slope Instability– Landslide
28
Source: Li et al., 2015 and co-author Steve Chrismer
![Page 29: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/29.jpg)
Common Questions
• Damage analysis– Load Increase Ratio4
• Traffic volume changes• Wheel load changes• Track condition changes• Maintenance requirements
29
Source: Ebersohn, 1997
![Page 30: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/30.jpg)
Design for Risk Mitigation• Roadbed Design provides ballast
requirements for subgrade condition based on traffic volume and design load
• Convert design life into a degradation forecast as basis for design validation
– Did track meet life expectation– Is track deteriorating faster than design– Possible causes:
• Increased Load• Inadequate ballast performance• Weaker Subgrade• Environmental Conditions• Incorrect design approach/constraints
• Better questions , better maintenance plan
30
Source: Li et al., 2015 and co-author Jim Hyslip
![Page 31: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/31.jpg)
Summary
![Page 32: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/32.jpg)
Summary
• Ballast Design methodology assesses tradeoffs among:
– required ballast thickness– design life requirements – traffic volume – design wheel load
• Railroad environment is changing – Understanding the tradeoffs provides insight
• Risks associated with changes are difficult to evaluate
– Setting performance expectations can help mitigate risks
32
![Page 33: Ballast Thickness Design for Changing Environment(s)](https://reader030.fdocuments.us/reader030/viewer/2022012803/61bd1a0c61276e740b0f5e1b/html5/thumbnails/33.jpg)