Large-Scale Direct Shear Testing of Common Open-Graded Aggregates

Manufactured open-graded aggregates are increasingly being used as backfill material for many geotechnical assets including retaining walls, bridge abutments, and foundations because of their free-draining and constructability advantages over traditional well graded materials. In design, many transportation agencies often use a default friction angle of 34 degrees, regardless of the material selected. To study the strength properties of open-graded aggregates, testing was performed on a large-scale direct shear device (LSDS) at the Federal Highway Administration's (FHWA's) Turner-Fairbank Highway Research Center. The LSDS device is 0.3 m x 0.3 m x 0.2 m and is capable of testing aggregates up to 30 mm. For this series of experiments, five commonly used open-graded aggregates are tested at four applied normal stresses, 34, 69, 138, and 207 kPa, at a shear rate of 0.4 mm/min and a gap size equal to the D85 of the material (i.e., the aggregate size where 85% of the sample is smaller). Results indicate that friction angles for these uncompacted open-graded aggregates are all greater than 45 degrees, well above the 34-degree default value.


  • English

Media Info

  • Media Type: Web
  • Features: References;
  • Pagination: pp 47-53
  • Monograph Title: Geo-Congress 2014 Technical Papers: Geo-Characterization and Modeling for Sustainability

Subject/Index Terms

Filing Info

  • Accession Number: 01522547
  • Record Type: Publication
  • ISBN: 9780784413272
  • Files: TRIS, ASCE
  • Created Date: Mar 25 2014 3:03PM