<p><p><h2>Preferred QC/QA Procedures</h2>Compaction grouting has no recommended or listed Federal Highway Administration quality control and quality assurance methods. However, there are several QC/QA methods that are commonly used in practice. The methods reviewed as part of the SHRP 2 assessment included active construction monitoring, SPT/CPT verification testing, and verification through geophysical methods. Active construction monitoring is the most commonly used method and is primarily a quality control method. Implementation requirements for this method are relatively low and inexpensive. SPT/CPT verification testing can be performed post-grouting as a means of quality assurance. Verification using geophysical methods is a more recently developed but less commonly used method of quality assurance. Active construction monitoring and SPT/CPT verification testing are the preferred methods.</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 compaction grouting are listed in Tables 1, 2, and 3. The entries in the tables 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-1939'><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 >•Verify material quality and mix
</td></tr><tr><td ><center>QC</td><td ><center>Process Control</td><td >•Monitoring grout pressures and volume takes
•Density of surrounding soil
</td></tr><tr><td ><center>QA</td><td ><center>Material Related</td><td > •Verify material quality and mix records</td></tr><tr><td ><center>QA</td><td ><center>Process Control</td><td >•Density of surrounding soil
•Verify records of grout pressures and volume takes
</td></tr></tbody></table><br><h3>TABLE 2. PERFORMANCE CRITERIA USE IN QC/QA MONITORING PROGRAMS</h3><table class='tablepress' id='tablepress-1940'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Parameters</td><td >•None noted
</td></tr><tr><td ><center>System Behavior</td><td >•Increase in density
•Settlement
•Heave of the ground surface
</td></tr></tbody></table><br><h3>TABLE 3. EMERGING QC/QA PROCEDURES AND MEASUREMENT ITEMS</h3><table class='tablepress' id='tablepress-1941'><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 >•Geophysical methods</td></tr></tbody></table></p></p>
<p><p><h2>QC/QA Guidelines</h2>A full QC/QA program should be outlined prior to a compaction grouting project. The success of a compaction grouting program is heavily reliant on how well procedures are monitored in the field. Improper grout rheology, hydraulic fracturing, and insufficient overburden pressure are common problems encountered that can be easily corrected if they are observed early in a project. Daily records should be kept and reviewed during grouting. Secondary and tertiary grout injections should indicate a decrease in volume of grout take. A drop in pressure on the order of 10 kPa could indicate hydraulic fracturing of the soil layer. Grouting should be advanced to the next stage if hydraulic fracturing occurs. Grout pressures should be decreased to avoid further fracturing of the soil layer. Grout rheology is important to assure the grout behaves in a predictable manner in the ground. The grout mix should be verified daily, and if ready mix grout is being used, truck tickets should be kept and the mix designation verified for each truck. If SPT/CPT verification is being used on a project, post-grouting test locations should be placed near pre-treatment test locations to assess the degree of improvement. Test locations should be placed evenly over a site or at critical locations. Typically test locations should be placed between grout injections at the ‘weak link’ (this may vary depending on the chosen layout) to assure the minimum requirements are met.</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 stays on schedule.</li></ul>Additional technology-specific details for inspections, construction observations, daily logs, and record keeping QC/QA activities are provided in the <em>Individual QC/QA Methods </em>section below.</p></p>
<p><p><h2>References</h2>Bandimere, S.W. (1997). “Comaction Grouting Sate of Practice 1997.” Geo-Logan 1997, GSP-66: Grouting: Compaction, Remediation, and Testing.</p><p>Byle, M.J. (2000). “An Approach to the Design of LMD Grouting.” Geo-Denver 2000, GSP 104: Advances in Grouting and Ground Modification.</p><p>Geraci, J. (2007). “Time-history compaction grouting data obtained through instrumentation.” GeoDenver 2007, GSP-168: Grouting for Ground Improvement: Innovative Concepts and Applications.</p><p>Graf, E. (1992). “Compaction Grout, 1992.” Grouting Soil Improvement and Geosynthetics. Geotechnical Special Publication No. 30. Reston, VA, American Society of Civil Engineers.</p><p>Gularte, F.B., Taylor, G.W., and Shao, L.S. (2007). “Observational monitoring methods for improved grouting and soil improvement.” GeoDenver 2007, GSP-168: Grouting for Ground Improvement: Innovative Concepts and Applications.</p><p>Haramy, K.Y., Henwood, J.T., and Szynakiewiez, T. (2009). “Assessing the Effectiveness of Compaction Grouting Using Seismic Methods.” Geo-Institute 2009, GSP-187: Contemporary Topics in Ground Modification, Problem Soils, and Geo-Support.</p></p>