DP-103 Soil Nail Walls
Nails That Bite the Dirt

The basic concept of soil nailing is to reinforce and strengthen the existing ground by installing closely spaced steel bars, called "nails," into a slope or excavation as construction proceeds from the "top down." This process creates a reinforced section that is itself stable and able to retain the ground behind it. The reinforcements are passive and develop their reinforcing action through nail-ground interactions as the ground deforms both during and following construction. Nails work predominantly in tension, but are considered by some to also work in bending/shear under certain circumstances. Generally, the soil nails significantly increase the apparent cohesion of the soil through their ability to carry tensile loads. A construction facing is also usually required, and is typically shotcrete reinforced by welded wire mesh. For permanent walls, the shotcrete construction facing is typically covered by a cast-in-place concrete facing.

The primary objective of this project is to demonstrate the cost-effective and technically correct application of soil nailing by the U.S. transportation community. The project is directed toward geotechnical, structural, and construction engineers who design and construct geotechnical facilities (embankments, cut slopes, retaining walls, and structures). The demonstration project has four major elements:

  • 1.Soil Nailing Field Inspector's Manual.
  • 2.Manual for Design, Construction and Monitoring of Soil Nail Walls (Including Guide Specifications).
  • 3.2-day workshop on soil nail wall design and construction.
  • 4.Project-specific Technical Assistance, including:
    • Technical assistance on the feasibility, design, and construction monitoring aspects of soil nail walls on specific projects.
    • Onsite construction inspector training.

Project development included the following: a summary report for a 1992 European scanning tour titled FHWA Tour of Geotechnology Soil Nailing was prepared and distributed in early 1993. The French soil nailing manual, Recommendations Clouterre 1991, has been translated into English and was distributed in 1994. The FHWA Soil Nailing Field Inspector's Manual has been prepared and was also distributed by OTA in 1994. A testing program to determine ultimate structural capacities of soil nail wall shotcrete facings was conducted at UC San Diego and will be completed late in the summer of 1995. The facing test program included testing fullsize test panels to failure and analytical modeling, and was a cooperative program co-sponsored by FWHA, Caltrans, and Industry. A Manual for Design, Construction and Monitoring of Soil Nail Walls And a 2day training workshop were developed and are now available to State DOTs. The manual is "practitioner oriented" and includes step-by-step design procedures, hand calculation worked design examples, example plan details, and guide construction specifications. A proprietary computer design program, "Goldnail" is demonstrated during the workshop and is distributed to each State under a specific lisencing agreement with the program developer. Project-specific design and construction technical assistance, including field inspector training, is now available.

Technical assistance is being provided to several States during the project. A team of Federal Highway, State Highway, and private consultants also traveled to Europe to investigate soil nailing techniques. The results of their trip are incorporated into the project.

Soil Nailing Field Inspectors Manual
(FHWA-SA-93-068) is available from NTIS and OTA.

Manual for Design, Construction and Monitoring of Soil Nail Walls, FHWA-SA-96-069 is available from NTIS.

English translation of the French manual
"Recommendations Clouterre1991" (Soil Nailing Recommendations1991, FHWA-SA-93-026) is available from NTIS.

"FHWA Tour for Geotechnology Soil Nailing"
(FHWA-PL-93-02 is available from HPI-10; Attention Mr. Steve Gaj)

U.S. Department of Transportation
Federal Highway Administration


Project Manager
Richard Cheney
(202) 366-1568

Project Coordinator
John M. Hooks
HTA-22, (202) 366-6712; Fax (202) 366-7909