Effective Shoulder Design and Maintenance

Granular shoulders are an important element of the transportation system and are constantly subjected to performance problems due to wind- and water-induced erosion, rutting, edge drop-off, and slope irregularities. Such problems can directly affect drivers’ safety and often require regular maintenance. The present research study was undertaken to investigate the factors contributing to these performance problems and to propose new ideas to design and maintain granular shoulders while keeping ownership costs low. This report includes observations made during a field reconnaissance study, findings from an effort to stabilize the granular and subgrade layer at six shoulder test sections, and the results of a laboratory box study where a shoulder section overlying a soft foundation layer was simulated. Based on the research described in this report, the following changes are proposed to the construction and maintenance methods for granular shoulders: (1) A minimum California bearing ratio (CBR) value for the granular and subgrade layer should be selected to alleviate edge drop-off and rutting formation; (2) For those constructing new shoulder sections, the design charts provided in this report can be used as a rapid guide based on an allowable rut depth. The charts can also be used to predict the behavior of existing shoulders; and (3) In the case of existing shoulder sections overlying soft foundations, the use of geogrid or fly ash stabilization proved to be an effective technique for mitigating shoulder rutting.

• Record URL:
  http://www.ctre.iastate.edu/reports/shoulder-design-tr531.pdf
• Record URL:
  http://publications.iowa.gov/5312/1/tr531.pdf
• 
• Corporate Authors:

  Iowa State University, Ames

  Center for Transportation Research and Education, 2711 South Loop Drive
  Ames, IA  United States  50011-8664

  Iowa Department of Transportation

  800 Lincoln Way
  Ames, IA  United States  50010
• Authors:
  • White, David J
  • Jahren, Charles T
  • Suleiman, Muhannad T
  • Mekkawy, Mohamed M
  • Smith, Duane E
• Publication Date: 2007-6

Language

• English

Media Info

• Media Type: Web
• Edition: Final Report
• Features: Appendices; Figures; Photos; References; Tables;
• Pagination: 296p

Subject/Index Terms

• TRT Terms: California bearing ratio; Design; Design charts; Dropoffs (Pavements); Erosion; Field studies; Fly ash; Geogrids; Granular materials; Laboratory studies; Road shoulders; Rutting; Soil stabilization; Subgrade (Pavements)
• Subject Areas: Design; Geotechnology; Highways; Pavements; I22: Design of Pavements, Railways and Guideways; I23: Properties of Road Surfaces; I42: Soil Mechanics;

Filing Info

• Accession Number: 01054752
• Record Type: Publication
• Report/Paper Numbers: IHRB Project TR-531, CTRE Project 05-198
• Files: TRIS, STATEDOT
• Created Date: Jul 31 2007 3:11PM