GEOGRID REINFORCEMENT OF GRANULAR BASES

A pavement reinforcement project was carried out at the University of Waterloo to address the very common situation where the strength of the road structure is primarily derived through the granular base. The objectives of the project were to develop equivalency factors for geogrid reinforced granular base sections and to provide data for developing structural design guidelines. A high strength, polymeric geogrid known as TENSAR was used. The experimental program consisted of repeated loads test on varying thicknesses of reinforced and unreinforced granular bases, varying reinforcement locations and varying subgrade strengths. A thin asphalt surface was used for all tests. Six "Loops" were constructed, with four sections tested in each Loop. The results can be summarized as follows: 1. For properly designed pavement sections, savings in granular base thickness consisted to about 100 mm. Alternatively, up to 3 times the number of loads could be carried to equal levels of 20 mm permanent deformation. For thinner granular sections, in the order of 150-100 mm, the absolute savings were understandably less but still about 25%, or 3 times the number of load carried. 2. For underdesigned sections with very weak subgrades, the initial benefits of reinforcement are not apparent; however, if a criterion of high permanent deformation of 38 mm (1.5 in.) is used, then the same savings as in 1. above can be realized. 3. Placing the geogrid in a very weak subgrade allowed twice the number of loads to be carried which suggests that the Tensar geogrid may be viable for subgrade stabilization. 4. A double layer of geogrid, for very weak subgrade conditions, allowed 3 times the number of loads to be carried. 5. Layer coefficient ratios (reinforced to unreinforced) for granular bases were determined, based on the AASHTO method, and ranged from 1.4 to 1.8. 6. Use of elastic layer theory to model pavement sections tested provided a linear relationship between predicted subgrade strains and the number of applied loads to failure. Several recommendations for future work have been developed. These include field verification of the design relationships, further field trials, and further evaluation. (Author)

• Supplemental Notes:
  • Paper presented during the Proceedings of the Roads and Transportation Association of Canada, Annual Conference, September 1985, Vancouver British Columbia. Volumes 1 and 2.
• Corporate Authors:

  Transportation Association of Canada (TAC)

  401-1111 Prince of Wales Drive
  Ottawa, Ontario  Canada 
• Authors:
  • Penner, R
  • Haas, R
  • Walls, J
  • Kennepohl, G
• Conference:
  • RTAC Annual Conference Proceedings - 1985
• Publication Date: 1985

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 263-293

Subject/Index Terms

• TRT Terms: Elasticity (Mechanics); Geotextiles; Granular bases; Guidelines; Material reinforcement; Pavement layers; Savings; Structural design; Thickness
• Old TRIS Terms: Elastic theory
• Subject Areas: Geotechnology; Highways; Materials; Pavements; I33: Other Materials used in Pavement Layers;

Filing Info

• Accession Number: 00453613
• Record Type: Publication
• Report/Paper Numbers: Volume 1
• Files: TRIS
• Created Date: Jul 31 1986 12:00AM