NEW CONCEPTS IN SUB-GRADE DESIGN

Engineers in Pakistan generally use soaked CBR values which results in an uneconomical (thicker) pavement in most cases. This study introduces the concept of Equilibrium Moisture Content and ISO-CBR curves for the quantification of sub-grade strength. The equilibrium moisture content is measured away from the pavement edge after the construction of the road and is not subject to seasonal changes. To determine the practical application of the concept, three soil samples from the vicinity of Rawalpindi - Islamabad were used and modified ISO-CBR charts produced. These charts can serve as ready-reckoning for determining sub-grade CBR at a particular moisture content. The method produces a thinner pavement as compared to soaked CBR value. Although widespread use of the method has the potential for bringing about considerable savings in road construction, pavements fail prematurely even with thicker layers due to poor quality control.

• Corporate Authors:

  National Transport Research Centre

  Pakistan Ministry of Communications, Sector H-8/3, Old Saidpur Road
  Islamabad,   Pakistan 
• Authors:
  • Akhter, H
• Publication Date: 1996-8

Language

• English

Media Info

• Pagination: 20 p.

Subject/Index Terms

• TRT Terms: California bearing ratio; Flexible pavements; Pavement design; Pavement layers; Subgrade materials
• Geographic Terms: Pakistan
• Subject Areas: Design; Highways; Pavements; I22: Design of Pavements, Railways and Guideways;

Filing Info

• Accession Number: 00730967
• Record Type: Publication
• Report/Paper Numbers: NTRC-189
• Files: TRIS
• Created Date: Feb 3 1997 12:00AM