USE OF THE BENKELMAN BEAM IN DESIGN AND CONSTRUCTION OF HIGHWAYS OVER SOFT CLAYS

Four highway pavement test sections were built in July 1971 at the U.S. Army Cold Regions Resarch and Engineering Laboratory. Two sections were designed by using the Asphalt Institute full-depth criteria, and the other two were based on similar traffic volumes by using the U.S. Army Corps of Engineers reduced subgrade strength criteria to compare their performance under freeze-thaw conditions. The first 3 years' observations show that (a) the maximum frost penetrations of 35 to 40 in. (89 to 101.6 cm) were essentially the same beneath all four sections, (b) the thawing condition in the subgrade as compared with that in the full-depth sections existed a fraction of the time beneath the crushed-stone base course sections (2 or 3 days versus 11 to 20 days), (c) the subgrades beneath the full-depth sections were subjected to two times as many freeze-thaw cycles as the subgrades under the crushed-stone bases bacause of the thinner pavement structure (8 cycles versus 4 cycles), (d) moisture increases of 8 to 12 percent occurred each year in the top foot (0.3 meter) of subgrade directly beneath the full-depth sections and caused high Benkelman beam deflections of up to 0.12 in. (3 mm) in the thinnest (5-in. (12.7-mm)) section and visible transitory rutting, and (e) uniform frost heaves of at least 2 1/2 in. (6.4 cm) were measured on both full-depth sections and of 1 1/2 and 1/2 in. (3.8 and 1.3 cm) on the crushed-stone base sections each year. From September 1971 to May 1974, a total of 49,000 vehicles had traversed the sections. Of this total, there were over 12,000 equivalent 18-kip (80-kN) axle loads, and the bulk of the truck traversed the sections during the frost-melting period. Observations are continuing for a more comprehensive evaluation. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 71-84
  • Monograph Title: Pavement design, performance and rehabilitation
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00139563
  • Record Type: Publication
  • ISBN: 0309024854
  • Files: TRIS, TRB
  • Created Date: Sep 16 1976 12:00AM