Large-Scale Laboratory Testing of Timber Tie-Lateral Resistance in Two Ballast Materials

• Author / Creator

  Mulhall, Courtney, E

• For railway track geometry to meet regulatory requirements under normal operating conditions, railway ballast must provide sufficient lateral resistance to control track deformations. This implies that on tangent tracks the lateral resistance of the ballast must be sufficient to resist thermal rail expansion forces during hot summer months and contraction forces during cold winter months. The ballast must also resist lateral deformations associated with loaded trains traversing curves at the maximum allowable speed. Thus, when considering the suitability of a material to be used as ballast the ability of the material to resist lateral track deformations must be evaluated. For this research, the tie lateral resistance provided by two ballast materials, the McAbee Ballast and Gravel Ballast, was evaluated through material characterization and tie-lateral resistance tests. The McAbee Ballast consists of particles with rough, angular to sub angular faces (blasted and crushed faces) and is an important source of ballast material in Western Canada. The Gravel Ballast consists of particles with smooth, rounded faces (uncrushed faces) and/or rough, angular to sub-angular faces (crushed faces) and is being evaluated for use on branch-lines. Material characterization tests were completed on the McAbee Ballast and Gravel Ballast, including sieve analysis to determine particle size distribution, photogrammetry analysis to determine shape parameters (e.g., form and angularity indices), flakiness index tests to determine flakiness index, and Los Angeles Abrasion and Micro Deval tests to assess durability. Based on the material characterization tests results, the McAbee Ballast was expected to provide more tie lateral resistance than the Gravel Ballast because it was rougher, more angular, and contained less flaky-particles. A large-scale ballast box (1.52 m long, 1.27 m wide, 0.51 m high, and 0.005 m thick) was designed to complete tie lateral resistance tests for a wide range of test conditions and to determine the contribution of each component of tie lateral resistance (i.e., the base friction, crib friction, and shoulder resistance that develops at the tie-ballast interface) to overall tie lateral resistance. The research methodology considers three test configurations to determine the three components of tie lateral resistance, respectively. For each test, the ballast box is filled with ballast, and a single timber tie is placed on or in the ballast and pushed laterally up to 40 mm at a loading rate of 0.5 mm/sec. The test is then repeated under several normal loads, ranging from 5 kN (the estimated weight of the track superstructure) up to 160 kN (the maximum potential in-service ballast load). The test results are used to determine the peak lateral resistance per tie, and the relationship between lateral load and normal load for each material and test configuration. From the tie lateral resistance tests, it was determined that the Gravel Ballast provides 15% less tie lateral resistance than the McAbee Ballast. It was also determined that the base friction, crib friction, and shoulder resistance contribute 65% to 70%, 10% to 15%, and 15% to 20%, respectively, under a normal load of 10 kN; and 98%, less than 1%, and less than 2%, respectively, under a normal load of 160 kN. These results are based on the peak lateral resistance of a single timber tie in dry, clean, freshly-tamped ballast under normal loads ranging from 5 kN to 160 kN; and may vary for other test or in service conditions.

• Subjects / Keywords

  • Track superstructure
  • Timber tie
  • Railway
  • Track substructure
  • Lateral resistance
  • Ballast
  • Tie-ballast interface

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R30R9MK2W

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.