Selecting Backfill Materials for MSE Retaining Walls

Existing AASHTO specifications for construction of mechanically stabilized earth (MSE) retaining walls require the use of high-quality, free-draining, granular backfill. In many areas, the availability of high-quality structural backfill has been decreasing. It is anticipated that as backfill supplies decrease, costs will most likely increase. Research and practice indicates that many soils other than those classified as AASHTO A-1-a soils have high strength (friction angles higher than 34 degrees) and have been shown to be suitable as backfill within the reinforced zone of MSE retaining walls. An FHWA Report ("Mechanically Stabilized Earth Walls and Reinforced Soil Slopes: Design and Construction Guidelines," FHWA-SA-96-071) and a paper by Keller (Gordon Keller, "Experiences with Mechanically Stabilized Structures and Native Soil Backfill," Transportation Research Record No. 1474, Mechanically Stabilized Backfill and Properties of Geosynthetics and Geocomposites, pp. 30-38, TRB, Washington, DC, November 1995) indicate that backfill materials, outside the specified gradation and plasticity requirements for AASHTO A-1-a soil, have shown satisfactory performance for reinforced soil slopes and MSE retaining walls. In addition, the National Concrete Masonry Association approves the use of backfill other than A-1-a soils in MSE retaining walls. However, strict adherence to AASHTO requirements for plasticity and percentage of material passing sieve #200 preclude the use of soils other than those classified as AASHTO A-1-a for use as backfill in the reinforced soil zone for MSE walls. Given the successful performance of reinforced slopes and retaining walls with backfill other than A-1-a soils, there is a need to investigate the use of a wider range of soil types for backfill within the reinforced zone of MSE retaining walls. The objective of this research is to develop selection guidelines, soil parameters, testing methods, and construction specifications that will allow the use of a wider range of backfill materials within the reinforced zone of mechanically stabilized earth (MSE) retaining walls.

• Record URL:
  http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=721
• Supplemental Notes:
  • To be summarized in a National Cooperative Highway Research Program (NCHRP) Research Results Digest.

Language

• English

Project

• Status: Completed
• Funding: $689973
• Contract Numbers:

  Project 24-22

• Sponsor Organizations:

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590

  American Association of State Highway & Transportation Officials (AASHTO)

  444 North Capitol Street, NW, Suite 225
  Washington, DC  United States  20001

  National Cooperative Highway Research Program

  Transportation Research Board
  500 Fifth Street, NW
  Washington, DC  United States  20001
• Project Managers:

  Reynaud, David

• Performing Organizations:

  Geotesting Express, Incorporated

  ,    
• Principal Investigators:

  Marr, W

• Start Date: 20030723
• Expected Completion Date: 20121231
• Actual Completion Date: 20121231
• Source Data: RiP Project 8585

Subject/Index Terms

• TRT Terms: Backfill soils; Construction; Guidelines; Materials; Mechanically stabilized earth; Retaining walls; Specifications; Test procedures
• Subject Areas: Construction; Geotechnology; Highways; I30: Materials;

Filing Info

• Accession Number: 01547930
• Record Type: Research project
• Source Agency: National Cooperative Highway Research Program
• Contract Numbers: Project 24-22
• Files: RIP, USDOT
• Created Date: Dec 17 2014 1:00AM