Reformulation of the CBR Procedure. Report 1: Basic Report
Abstract
The California Bearing Ratio (CBR) procedure has been the principal method used for design of flexible pavements for both military roads and airfields since its development in the 1940s. In recent years, as the use of analytical models, such as the layered elastic and finite elements models, became accepted for pavement design, the CBR design procedure has been criticized as being empirical, overly simplistic, and outdated. A major criticism of the procedure has been the use of an adjustment, or Alpha factor, to account for over-estimation of the equivalent single-wheel load and as a thickness adjustment for traffic volume. The objective of this research was to reformulate the CBR-Alpha procedure so that design would be based on a more mechanistic methodology and to develop performance criteria for use with the reformulation. With this purpose in mind, the report details the developmental steps of the reformulation starting with the original CBR-Alpha procedure and ending with a new procedure based on Froehlich's theory for stress distribution. The reformulation was verified through review of historical test data, by prototype testing, and by analyses of an actual airfield pavement failure. The reformulation of the procedure resulted in the elimination of both the equivalent single-wheel load concept and the Alpha factor.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2012
- Accession Number
- ADA559867
Entities
People
- Alessandra Bianchini
- Carlos R. Gonzalez
- Walter R. Barker
Organizations
- Engineer Research and Development Center