00469504

Component

http://onlinepubs.trb.org...trr/1987/1131/1131-006.pdf

https://scholar.google.co...FTON&publication_year=1987

The performance of rock ballast, when subjected to the physical stresses of loading and to the chemical and physical stresses of weathering environment, depends to a great extent on the mineralogical, chemical, textural, and structural properties of the material. Because these properties can readily be identified by petrographic analysis, useful predictions of ballast performance can be made by the experienced petrographer. However, because of the difficulty of assessing these properties quantitatively and the large number of variable factors involved, petrographic evaluation of ballast remains, at this stage, largely a subjective process. Mineralogy is a major factor in determining overall rock hardness and physical durability, chemical weathering potential, composition and quantity of derived fines, and degree of susceptibility to wetting and drying. Rock texture also affects hardness and is important in influencing toughness, relative susceptibility to freeze-thaw degradation, and mechanical stability in track. Most of the standard tests commonly applied to ballast materials essentially provide a measure of a combination of petrographic properties; consequently, the results of the tests can be predicted to within certain limits. Numerous techniques, including the use of microscopes and X-ray diffraction equipment, can be applied in the study of the fines fraction of track samples to determine the nature and source of the material. Three ballast types in use by Canadian Pacific (CP) Rail (Kimberley Float, Walhachin, and Prairie gravels) are discussed to demonstrate the influence of petrographic properties on performance.

Publication of this paper sponsored by Committee on Railway Maintenance. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

01418149

pp 45-63

1987

Transportation Research Record

0309045150

Print

Appendices (1) ; Figures (1) ; References (14) ; Tables (4)

Aggregates by source; Ballast (Railroads); Diffraction; Drying; Durability; Fines (Materials); Freeze thaw durability; Hardness; Mechanical properties; Microscopy; Mineralogy; Performance evaluations; Petrography; Texture; Toughness; Weathering; Wetting; X rays

Aggregate sources; Ballast; X-ray diffraction

Geotechnology; Highways; Railroads; I36: Aggregates

TRIS, TRB, ATRI

Jul 31 1988 12:00AM

• APPLICATION OF PETROGRAPHIC ANALYSIS TO BALLAST PERFORMANCE EVALUATION
• COMPONENT IDENTIFICATION AND INVENTORY OF U.S. ARMY RAILROAD TRACKAGE
• EFFECTS OF PARTICLE CHARACTERISTICS ON BEHAVIOR OF GRANULAR MATERIAL
• PERFORMANCE OF LARGE-SCALE MODEL SINGLE TIE-BALLAST SYSTEMS
• PRODUCTION AND TESTING OF BALLAST
• RAILROAD TRACK STRUCTURE PERFORMANCE UNDER WHEEL IMPACT LOADING
• SUBGRADE AND BALLAST REQUIREMENTS FOR 125-TON CARS
• TRACK COMPONENTS FOR 125-TON CARS
• TRACK EVALUATION AND BALLAST PERFORMANCE SPECIFICATIONS
• USE OF GEOSYNTHETICS IN THE DESIGN OF RAILROAD TRACKS