<p><p><h2>QC/QA Procedures</h2>No guidance document exists which describes a comprehensive and thorough description of a QC/QA program for Sand Compaction Piles (SCPs). However, Kitazume (2005) and Barksdale (1987) provide valuable information about QC/QA methods, and these references should be reviewed when developing a QC/QA program. QC/QA involves testing and observation during pre-construction, construction, and post-construction phases. Before project execution, a preliminary survey should be performed and the SCP locations should be laid out. A typical comprehensive QC/QA program should include Standard Penetration Testing (SPT) and/or Cone Penetration Testing (CPT), a SCP installation log, confirmation of suitability of SCP particle size distribution and/or material quality, and surveying. For critical projects, a field trial test which installs SCPs into a small portion of the site should be completed to determine the effectiveness of the design. For sites where stability is a concern, inclinometers should be utilized to monitor lateral movement. Murakami et al. (2006) suggests additional testing to determine the SCP fill material water content, compactibility, and permeability for more critical projects. Piezometers and settlement plates are typically only used for SCPs in cohesive soils where a significant amount of settlement is anticipated upon loading. Equipment necessary for SCP projects is described in Kitazume (2005).</p><p>Construction 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 SCPs are shown in Tables 1, 2, and 3. 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-2038'><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 >• SCP particle size distribution
</td></tr><tr><td ><center>QC</td><td ><center>Process Control</td><td >• Location of SCP
• Diameter of SCP
• Length of SCP
• Amount of fill with depth
• SPT and CPT testing
</td></tr><tr><td ><center>QA</td><td ><center>Material Related</td><td > • SCP particle size distribution
</td></tr><tr><td ><center>QA</td><td ><center>Process Control</td><td >• Location of SCP
• Diameter of SCP
• Length of SCP
• Amount of fill with depth
• Improvement of soil between SCPs
• SPT and CPT testing
</td></tr></tbody></table><br><h3>TABLE 2. PERFORMANCE CRITERIA USE IN QC/QA MONITORING PROGRAMS</h3><table class='tablepress' id='tablepress-2039'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Parameters</td><td >•Density, strength, and stiffness of SCP
•Improvement of soil between SCPs
</td></tr><tr><td ><center>System Behavior</td><td >•Heave between SCPs
•Lateral displacement
•Settlement
•Bearing capacities of SCPs and composite ground
</td></tr></tbody></table><br><h3>TABLE 3. EMERGING QC/QA PROCEDURES AND MEASUREMENT ITEMS</h3><table class='tablepress' id='tablepress-2040'><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 >• None noted</td></tr></tbody></table></p></p>
<p><p><h2>QC/QA Guidelines</h2>SCPs are expected to serve as stiff elements for supporting an external load and as a drainage material. For this reason, confirming the specified particle size distribution of the SCP material is a critical part of the QC/QA processes for SCP projects. SCP materials should have a low fines content (preferably less than 5%) and high friction angle. Any fines in the SCP materials should be non-plastic. Materials other than sand are allowed to be substituted as fill material and are specified in Kitazume (2005), Murakami et al. (2006), and Tanimoto (1973). The adherence of the SCP fill material to specifications should be confirmed before construction.</p><p>SPTs are frequently used as part of the QC/QA processes for SCP improved sites. For SCPs in cohesive soils, SPT N-values are taken from the center of the pile. When SCPs are installed in cohesionless soils, SPT N-values are taken from the center of the pile in addition to testing points between piles. While the values taken from the field will need to be corrected for various considerations, the SPT test is fairly reliable and can be used to confirm the quality of the SCP installation. CPT tests can be performed in inter-pile clay soil and some sandy sites. Barksdale (1987) and Kitazume (2005) provide test frequency guidance.</p><p>Keeping records of depth of the casing tip, location of the SCP, power consumption, and volume of sand used is standard. These records should be kept for each individual SCP as the records serve to provide evidence of adhering to the design specifications. In addition, the records can be used to monitor any problems that may be encountered during installation and can be used to estimate SCP diameter changes with depth using equations provided in Kitazume (2005).</p><p>Surveying of the site surface prior to and during SCP installation is frequently done as a measure to monitor heaving which can be detrimental to the project success.</p><p>Inspections, construction observations, daily logs, and record keeping are essential QC/QA activities for all technologies. These activities help to ensure and/or verify that:<br><ul> <li>Good construction practices and the project specifications are followed.</li> <li>Problems can be anticipated before they occur, in some cases.</li> <li>Problems that do arise are caught early, and their cause can oftentimes be identified.</li> <li>All parties are in good communication.</li> <li>The project is on schedule.</li></ul>Additional technology-specific details for inspections, construction observations, daily logs, and record keeping QC/QA activities are provided in the following <em>Individual QC/QA Methods </em>sections.</p></p>
<p><p><h2>References</h2>Aboshi, H., Mizuno, Y., and Kuwabara, M. (1991). “Present state of sand compaction pile in Japan.”<em> Deep Foundation Improvements: Design, Construction, and Testing</em><strong>. </strong><u>ASTM</u> <u>STP</u> <u>1089</u>, Melvin I. Esrig and Robert C. Bachus, Eds., American Society for Testing and Materials, Philadelphia, PA.</p><p>Barksdale, R.D. (1987). <em>State of the Art for Design and Construction of Sand Compaction Piles</em>. Technical Report REMR-GT-4, prepared for Department of the Army, US Army Corps of Engineers, November, 55p.</p><p>Kitazume, M. (2005). <em>The Sand Compaction Pile Method</em>, Taylor & Francis, 232p.</p><p>Kuroda, K. and Kanada, Y. (1983). “New Quality Control Method and its Application to Construction of Sand Compaction Piles.” The 4<sup>th</sup> International Conference on Applications of Statistics and Probability of Soil and Structural Engineering.</p><p>Mitchell, J.K. (1981). “Soil Improvement: State of the Art Report.” <em>Proceedings of the Tenth ICSMFE, </em>Stockholm, Sweden, Vol. 4, pp 509-565.</p><p>Murakami, S., Higashi, S., Nakai, N., Seki, T., and Tsubio, H. (2006). “Characteristics of granular filling materials as sand compaction pile.” Geomechanics and Geotechnics of Particulate Media, pp 457-462.</p><p>Schaefer, V.R., Berg, R.R., Collin, J.G., Christopher, B.R., DiMaggio, J.A., Filz, G.M., Bruce, D.A., and Ayala, D. (2016). “Ground Modification Methods,” Federal Highway Administration, Washington, DC, FHWA NHI-16-028 (Vol. II), 542p.</p><p><a href="https://www.fhwa.dot.gov/engineering/geotech/pubs/nhi16028.pdf">https:/…, J., <a href="http://adsabs.harvard.edu/cgi-bin/author_form?author=Stokoe,+K&full…, K. H.</a>, <a href="http://adsabs.harvard.edu/cgi-bin/author_form?author=Roesset,+J&ful…, J. M.</a>, and <a href="http://adsabs.harvard.edu/cgi-bin/author_form?author=Hudson,+W&full…, W. R.</a> (1986) "Applications and Limitations of the Spectral-Analysis-of-Surface-Waves Method." Final Research Report Texas Univ., Austin. Center for Transportation Research.</p><p>Tanimoto, K. (1973). “Introduction to the Sand Compaction Pile Method as Applied to Stabilization of Soft Foundation Grounds.” Division of Applied Geomechanics Report No. 6, Commonwealth Scientific and Industrial Research Organization, Australia, pp 1-14.</p></p>