<p><p><h2>Preferred QC/QA Procedures:</h2>The Federal Highway Administration (FHWA) <em>Soil Nail Walls</em> reference manual (Lazarte et al. 2015) is considered to be the guidance document on Quality Control and Quality Assurance (QC/QA) programs for general soil nail walls and is referenced herein. However, no document exists that addresses QC/QA programs for shoot-in soil nailing projects specifically. A comprehensive QC/QA program for these projects should typically consist of proof and verification testing, creep testing (only applicable for soil nail walls in cohesive soils), surveying, visual inspection, and construction/material inspection. Projects including shotcrete in the final wall or slope need to incorporate shotcrete testing and inspection into the QC/QA program. Tension testing is a supplemental test that can be performed when deemed necessary.</p><p>The QC/QA guidance provided by the FHWA is summarized below.</p><p><table class='tablepress' id='tablepress-2041'><thead><th><center>Publication Title</th><th><center>Publication
Year
</th><th><center>Publication Number</th><th><center>Available for Download</th></thead><tbody><tr><td ><center>Soil Nail Walls Reference Manual</td><td > <center>2015</td><td > <center>FHWA-NHI-14-007</td><td > <center>Yes<sup>1</td></tr></tbody></table><br><p class="disclaimer"><sup>1</sup> <a href="https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi14007.pdf">https:/… quality is achieved by meeting established requirements, as detailed in project plans and specifications, including applicable codes and standards. Quality Control (QC) and Quality Assurance (QA) are terms applied to the procedures, measurements, and observations used to ensure that construction satisfies the requirements in the project plans and specifications. QC and QA are often misunderstood and used interchangeably. Herein, Quality Control refers to procedures, measurements, and observations used by the contractor to monitor and control the construction quality such that all applicable requirements are satisfied. Quality Assurance refers to measurements and observations by the owner or the owner's engineer to provide assurance to the owner that the facility has been constructed in accordance with the plans and specifications.</p><p>The components of QC/QA monitoring programs for shoot-in soil nailing are shown in Tables 1, 2, and 3<em>.</em> The entries in the table are a list of typical items, not a list of all methods that could be used for QC/QA. Some QC procedures and measurement items may also serve as QA procedures and measurement items.<br><h3>TABLE 1. TYPICAL EXISTING QC/QA PROCEDURES AND MEASUREMENT ITEMS</h3><table class='tablepress' id='tablepress-2045'><thead><th><center>QC or QA</th><th><center>Material or Process</th><th><center>Items</th></thead><tbody><tr><td ><center>QC</td><td ><center>Material Related</td><td >•Verification of material quality
</td></tr><tr><td ><center>QC</td><td ><center>Process Control</td><td >•Location, angle, and depth of nails in slope
</td></tr><tr><td ><center>QA</td><td ><center>Material Related</td><td >•Verification of shotcrete strength
</td></tr><tr><td ><center>QA</td><td ><center>Process Control</td><td >•None noted</td></tr></tbody></table><br><h3>TABLE 2. PERFORMANCE CRITERIA USE IN QC/QA MONITORING PROGRAMS</h3><table class='tablepress' id='tablepress-2046'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Parameters</td><td >•Nail pullout capacity, facing quality/strength
</td></tr><tr><td ><center>System Behavior</td><td >•Wall movement, creep
</td></tr></tbody></table><br><h3>TABLE 3. EMERGING QC/QA PROCEDURES AND MEASUREMENT ITEMS</h3><table class='tablepress' id='tablepress-2047'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Related</td><td >• None noted</td></tr><tr><td ><center>Process Control</td><td >•Automated surveying equipment</td></tr></tbody></table></p></p>
<p><p><h2>QC/QA Guidelines</h2>Proof and verification load tests are effective in establishing the nail-ground interface strength. Proof and verification tests load the nail to a specified percentage of the design load. Verification tests load sacrificial nails to at least 200% of the design load. Results from verification tests are used to produce final design values. One or two verification load tests should be completed prior to production soil nail installation. During soil nail installation, at a minimum, two verification load tests should be performed in every different soil strata encountered. Larger projects will require more verification load tests (Lazarte et al. 2015 and Porterfield, Cotton, and Byrne 1994). Proof tests are conducted similarly to verification tests but load the nail up to approximately 150% of the design load. Proof tests occur during production nail installation and can be conducted on production nails. Proof tests are usually performed on 5% of the installed nails (Lazarte et al. 2015). Results from proof tests are used to assure consistent and acceptable installation methods and pullout capacity.</p><p>The creep test is normally conducted as part of a proof or verification test, in which the load test is paused at a specified load ceiling while deformations in the soil nail over time are measured. The creep test can indicate how the loaded nail will behave throughout its service life under a constant load. Creep testing is typically only performed for projects where the soil nails are installed in cohesive soils where creep may be an issue. Creep tests should be performed at the same frequency as verification testing. Records of proof, verification, and creep test results should be kept to confirm design values have been achieved and adherence to the method and performance approach specifications. This will help to assure the wall’s longevity and ability to sustain the design load.</p><p>Visual inspection rapidly covers large areas and identifies visible problems such as cracking, seepage, and bulging, which may indicate failure. Inspection does not provide quantifiable results, but can identify major concerns that should have been addressed in the specifications. The wall should be visually inspected on a regular schedule in order to counteract a potential wall failure. Surveying is useful for monitoring the entire soil nail wall during and after construction for slope movements. Surveying is a more accurate and refined method to monitor wall movements. During construction, inspection of construction materials and activities verify that samples from each batch of material conform to the design specifications and that proper construction procedures are followed. Lazarte et al. (2015) provides a list of every item an inspector should verify and record in nail installation logs as part of project quality assurance.</p><p>Shotcrete cores are tested for compressive strength. Sampling, testing methods, and test frequency are described in Lazarte et al. (2015) and Byrne et al. (1998). These procedures help confirm that strength and property values defined in the specifications have been achieved.</p><p>In the laboratory, tension testing of representative nails verifies the batch’s ultimate tensile strength. Tension testing provides highly accurate and precise results for the strength of the nail, which can be used as a QC tensile strength verification test. However, because nails come with certificates, the tension test is rarely used.</p></p>
<p><p><h2>References</h2>Beekman, A. and Mallner, A. (2005). “Fiberglass Nail Pullout Capacity for Rapid Landslide Remediation.” EFRI at Rose-Hulman Institute of Technology, July 2005.</p><p>Byrne, R.J., Cotton, D. Porterfield, J., Wolschlag, C., and Ueblacker, G. (1998). “Manual for Design and Construction Monitoring of Soil Nail Wall.” FHWA-SA-96-069R.</p><p>Lazarte, C.A., Robinson, H., Gómez, J.E., Baxter, A., Cadden, A., and Berg, R.R. (2015). “Soil Nail Walls Reference Manual,” FHWA NHI-14-007, GEC No. 7, Federal Highway Administration, Washington, DC, 425p.</p><p><a href="https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi14007.pdf">https:/…, J.A., Cotton, D.M., and Bryne, R.J., (1994) <em>Soil Nailing Inspectors Manual – Soil Nail Walls, </em>FHWA-SA-93-068, Federal Highway Administration.</p><p>Rogbeck et al. (2003). “Nordic Guidelines for Soils and Fills.” The Nordic Geotechnical Societies Nordic Industrial Fund.</p><p><strong> </strong></p></p>