EVALUATING PERMISSIBLE SUBGRADE RUT DEPTH IN PAVEMENT DESIGN

In the design of a pavement, the permissible rut depth and permissible resilient vertical strain at the top of the subgrade at the end of the construction stage (i.e. before the placing of the bituminous layer) are used to select the appropriate thickness of granular material. However, usually the only available data for the subgrade is the resilient modulus, which is estimated from the California Bearing Ratio. This paper examines the application of a new three-surface kinematic hardening model for the subgrade in a finite-element analysis to evaluate the rut depth and resilient vertical strain at the top of the subgrade at the end of the construction stage. The resilient modulus for the subgrade is determined by examining the stress changes at different depths in the subgrade, for different thicknesses of granular material, and applying such stress changes to simulated triaxial samples for 50 cycles to compute the resilient modulus at different depths for input to a layered elastic analysis, in order to compute the resilient strain at the top of the subgrade. This is used to estimate the required thickness of granular layer based on the allowable subgrade strain, and it is found that a realistic thickness is obtained. The new three-surface kinematic hardening model is also used to calculate the rut depth at the end of construction for different thicknesses of granular material, and the permissible rut depth criterion is used to select the required thickness of granular material. A realistic thickness is also obtained using this criterion, so that, by using the new kinematic hardening model, the permissible rut depth and subgrade strain criteria are seen to be consistent. The model is then applied to a thinly surfaced pavement to investigate the effect of the thickness of granular material and asphalt on the predicted rut depth. (A)

  • Availability:
  • Corporate Authors:

    Thomas Telford Limited

    London,   United Kingdom 
  • Authors:
    • HAU, K W
    • McDowell, G R
  • Publication Date: 2005-1

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00987082
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, ATRI
  • Created Date: Mar 3 2005 12:00AM