<p><p><figure id='attachment_2571' style='max-width:932px' class='caption aligncenter'><img class="wp-image-2571 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Cross-section diagram showing the typical layout of soil nails in a wall." width="932" height="553" /><figcaption class='caption-text'> Typical Cross Section of Soil Nail Wall, Lazarte et al. (2003)</figcaption></figure><h2>Basic Function:</h2>Provides slope or cut stability to provide in‑situ reinforcement. The nails act together along with a face protection and drainage system.<br><h2>Advantages:<em> </em></h2><ul> <li>More economical than using competing systems</li> <li>Quick construction</li> <li>Wall flexibility</li> <li>Less right of way needed</li> <li>Can be used in areas of limited headroom</li></ul><h2>General Description:</h2>In soil nailing, the steel reinforcement, or nails, are drilled and grouted into the soil to provide reinforcement. They can be installed with a slope protection and drainage system. The nails are then bonded to the soil over the entire length. The hollow bar system drills and grouts at the same time.<br><h2>Geologic Applicability:</h2><ul> <li>Stiff to hard fine grain with a plasticity index less than 15 and a SPT N-value greater than 9</li> <li>Dense to very dense granular soils with some apparent cohesion and a SPT N-value greater than 30</li> <li>Weathered rock with no weakness planes or karsts and well-graded glacial soils</li> <li>Poor soils including cohesionless and poorly‑graded loose soils, soils with cobble and boulders, soft to very soft fine grain soils with SPT N-values less than or equal to 4, highly corrosive soils, and soils susceptible to liquefaction or collapse after introduction to water</li> <li>Water table behind the wall increases the difficulty of construction</li></ul><h2>Construction Methods:</h2>Soil nails are installed in regular patterns and act together to provide reinforcement. The spacing of the soil nails should be no larger than 3 to 6 feet (0.9 to 1.8 meters) apart. The nail length to wall height ration should be 0.7 to 0.8. The nails are not prestressed. The nail is bonded by cement grout to the soil over its length. When using a hollow bar system the bars are drilled and grouted simultaneously. If using shotcrete for the face protection, the shotcrete thickness should be between 2 to 6 inches (50 to 150 mm) or 6 to 10 inches (150 to 250 mm) for permanent structures.<br><h2>Additional Information:</h2>More is known about drilled/grouted nails from experience compared to the hollow steel bar system. Because of this, drilled/grouted nails are recommended for permanent construction. QC/QA procedures are still being developed for the hollow bar soil nail wall system. Factors that determine the cost of the project include the type of soil, site accessibility, level of corrosion protection, wall size, facing type, application, and the skill and availability of contractor.<br><h2>SHRP2 Applications:</h2><ul> <li>Embankment Widening</li></ul><h2>Example Successful Applications:</h2><ul> <li>Bellevue Technology Tower – Bellevue, Washington</li> <li>Landslide Stabilization US Highway 26-89 MP 131.8 – Wyoming</li></ul><h2>Complementary Technologies:</h2>Can use complementary technologies or used alone. Tiebacks or anchors can be used to increase stability and decrease settlement. This technology can also be used as the shoring in a MSE Wall System.<br><h2>Alternate Technologies:</h2>Shoot-in/screw-in soil nailing, SMSE wall systems, MSEW, modular block/geosynthetic wall, Tecco mesh/shotcrete facing system, and reinforced soil slopes.<br><h2>Potential Disadvantages:</h2><ul> <li>Limited treatment depth</li> <li>Lack of bending resistance</li> <li>Difficult to install in clean sands when the groundwater table is above the bottom of the pier</li> <li>Not applicable to wide heavy-load applications</li> <li>Usually only effective to a depth of 7 to 30 feet (2 to 9 meters) below foundation</li></ul><h2>Key References for this technology:</h2>Byrne, Porterfield, Cotton, Wolschlag, and Ueblacker. (1998). “Manual for Design and Construction Monitoring of Soil Nail Walls.” FHWA –SA-96-069R.</p><p>Lazarte, C.A., Elias, V., Espinoza, R.D., and Sabatini, P.J., (2003) <em>Geotechnical Engineering Circular No. 7 Soil Nail Walls, </em>FHWAA0-IF-03-017, Federal Highway Administration, March, 2003.</p><p>Samtani, N.C. and Nowatzki, E.A. (2006). “Hollow Core Soil Nails State of the Practice.” FHWA, Publication No. Unassigned. April 2006. 55 pages.</p></p>