<p><p><h2>Preferred QC/QA Procedures</h2>Deep dynamic compaction has no standard quality control or quality assurance measures. The Federal Highway Administration (FHWA) design guidance document, Lukas (1995), does include a section on construction monitoring that may serve as a quality control guide. A basic QC/QA program for deep dynamic compaction should always include heave and crater depth measurements after each series of tamper drops, settlement measurements after the ground has been leveled subsequent to each pass, and SPT or CPT measurements both before and after the compaction program. In addition, vibration monitoring should be carried out throughout the compaction program to control construction and avoid damage to surrounding structures. Porewater pressure should be monitored during compaction of saturated soils to ensure the initial soil structure has been broken down and excess pore pressures have dissipated between successive tamper drops. Dilatometer (DMT) and pressuremeter (PMT) tests can be used in the same manner as CPTs or SPTs, but there are fewer correlations between measurements and soil properties. Load tests can be performed in ground conditions where SPTs and CPTs may not be possible, such as in soils containing large amounts of cobbles and boulders. Load tests are also performed at landfill sites because of the difficult SPT/CPT conditions. However, they are time consuming and expensive to perform.</p><p>For projects requiring the improvement of large areas, it is desirable to subdivide the total area into approval or acceptance zones on the order of 100 feet on a side. Completing the work with timely approval on a zone-by-zone basis means that the contractor may proceed without risk of having to return later in the project to correct deficiencies that developed early in the project.</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>Table 1 shows the components of QC/QA monitoring programs for deep dynamic compaction. 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-149'><thead><th>QC or QA</th><th>Material or Process</th><th>Items</th></thead><tbody><tr><td >QC</td><td >Material Related</td><td >• Relative density before and after densification (from CPT, SPT, or shear wave velocity)
• Plate load test results</td></tr><tr><td >QC</td><td >Process Control</td><td >• Grid layout
• Height of drops
• Number of drops
• Vibration monitoring
• Porewater pressure monitoring
• Crater depth monitoring
• Surrounding heave monitoring</td></tr><tr><td >QA</td><td >Material Related</td><td >• Relative density before and after densification (from CPT, SPT, or shear wave velocity)
• Plate load test results</td></tr><tr><td >QA</td><td >Process Control</td><td >• Grid layout
• Height of drops
• Number of drops
• Vibration monitoring
• Porewater pressure monitoring
• Crater depth monitoring
• Surrounding heave monitoring</td></tr></tbody></table><br><h3>Table 2. Performance Criteria use in QC/QA monitoring programs</h3><table class='tablepress' id='tablepress-150'><thead><th>Topics</th><th>Items</th></thead><tbody><tr><td >Material Parameters</td><td >• Settlement plate results
• Relative density before and after densification
• CPT penetration resistance
• SPT N-value</td></tr><tr><td >System Behavior</td><td >• Surface settlement</td></tr></tbody></table><br><h3>Table 3. Emerging QC/QA Procedures and Measurement Items</h3><table class='tablepress' id='tablepress-151'><thead><th>Topics</th><th>Items</th></thead><tbody><tr><td >Material Related</td><td ></td></tr><tr><td >Process Control</td><td >• Automated settlement measurements</td></tr></tbody></table></p></p>
<p><p><h2>QC/QA Guidelines</h2>QC/QA programs should take the following considerations into account:<br><ol> <li>Spacing between CPT or SPT tests (testing frequency):<br><ol style="list-style-type: lower-alpha;"> <li>Specify at least one full post-treatment test profile (SPT or CPT) per 1000 m<sup>2</sup>with at least four tests. This can be reduced in uniform soil conditions to one every 1500 m<sup>2</sup>, and on large sites this can be reduced to one per 2000 m<sup>2</sup>. (Dumas and Beaton 1992)</li></ol></li> <li>If load tests are required (usually in landfills), the number is likely to depend on the size of the treatment area. Han (1998), Lukas (1986), and Lukas (1995) report from one to six load tests for some specific cases.</li> <li>Minimum time between the end of compaction and verification testing:<br><ol style="list-style-type: lower-alpha;"> <li>This should be after all excess pore pressures have dissipated. This can range from days in pervious soils to months in semi-pervious soils. (Lukas 1986)</li></ol></li> <li>Minimum value of penetration resistance or other measured propertyis based on project requirements. Maximum realistically achievable values are listed below in Table 1</li> <li>Project specific requirements for minimum percentages of failing tests, lowest acceptable values, and their distribution throughout a site should be included. As an example, Lukas (1986) states, using relative density as a measure:<br><ol style="list-style-type: lower-alpha;"> <li>The overall average measured values should be at least XX; e.g., a relative density of 85%, with no average of three consecutive values less than a slightly smaller value of XX; e.g., a relative density of 75%</li> <li>Tests within the upper XX feet; e.g., 15 feet, should have no values less than the specified average acceptance criterion. Below this depth no value should be less than a specified minimum value.</li> <li>Values less than a specified minimum should be reported to the Engineer for review and acceptance.Project specific requirements for minimum percentages of failing tests, lowest acceptable values, and their distribution throughout a site should be included. As an example, Lukas (1986) states, using relative density as a measure:</li></ol></li> <li>Maximum levels of vibration at different locationsshould be limited to:<br><ol style="list-style-type: lower-alpha;"> <li>50 mm/sec to avoid cosmetic damage in most modern buildings (Lukas 1986)</li> <li>0.25 in/sec (6.4 mm/sec) for historic buildings (Lukas 1986)</li></ol></li> <li>Minimum acceptable level of pore pressure generation</li></ol><h3>Table 4. Upper bound test values after dynamic compaction (Lukas 1995)</h3><table class='tablepress' id='tablepress-152'><thead><th>Soil Type</th><th>Maximum Test Value:
Standard Presentation Resistance (blows / 300 mm)</th><th>Maximum Test Value:
Static Cone Tip Resistance (MPa)</th><th>Maximum Test Value:
Pressuremeter Limit Pressure (MPa)</th></thead><tbody><tr><td >Pervious coarse-grained soil: sand and gravels</td><td ><center>40 – 50</center></td><td ><center>19 – 29</center></td><td ><center>1.9 – 2.4</center></td></tr><tr><td >Semipervious soil: sandy silts</td><td ><center>34 – 45</center></td><td ><center>13 – 17</center></td><td ><center>1.4 – 1.9</center></td></tr><tr><td >Semipervious soil: silts and clayey silts</td><td ><center>25 – 35</center></td><td ><center>10 – 13</center></td><td ><center>1.0 – 1.4</center></td></tr><tr><td >Partially saturated impervious deposits: clay fill and mine spoil</td><td ><center>30 – 40*</center></td><td ><center>N/A</center></td><td ><center>1.4 – 1.9</center></td></tr><tr><td >Landfills</td><td ><center>20 – 40*</center></td><td ><center>N/A</center></td><td ><center>0.5 – 1.0</center></td></tr></tbody></table><br><p class="disclaimer">*Higher test values may occur due to large particles in the soil mass.</p> </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>Dumas, J.C. and Beaton N.F. (1992). “Dynamic compaction, Suggested guidelines for evaluating feasibility- for specifying- for controlling.” <em>Canadian Geotechnical Conference Proceedings</em>, p. 54-1-54-12.</p><p>Elias, V., Welsh, J., Warren, J., Lukas, R., Collin, J. G., and Berg, R. R. (2006a). “Ground Improvement Methods”- Volume I. Federal Highway Administration Publication No. NHI-06-020.</p><p>Han, J. (1998). “Ground modification by a combination of dynamic compaction, consolidation, and replacement.” <em>Proceedings, Fourth International Conference on Case Histories in Geotechnical Engineering</em>, St. Louis, Missouri, 341-346.</p><p>Lukas, R.G. (1986). “Dynamic Compaction for Highway Construction Volume I: Design and Construction Guidelines.” U.S. Department of Transportation, Federal Highway Administration, Washington, D.C., FHWA/RD-86/133.</p><p>Lukas, R.G. (1995). “Dynamic Compaction – Geotechnical Engineering Circular No. 1”, U.S. Department of Transportation, Federal Highway Administration, Washington, D.C., FHWA-SA-95-037.</p><p>Mackiewicz, S.M. and Camp, W.M. (2007). “Ground Modification: How Much Improvement?”, <em>Soil Improvement, Geotechnical Special Publication No. 172</em>, ASCE</p><p>Miller, H., Stetson, H., and Benoit, J. (2004). “DMT testing for site characterization and QA/QC on a deep dynamic compaction project.” <em>Geotechnical Special Publication No. 126</em>, ASCE, p. 1805-1812.</p><p>Mitchell, J.K. (1981) "Soil Improvement: State-of-the-Art," <em>Proceedings of the Tenth International Conference. on Soil Mechanics. and Found. Engineering</em>, Stockholm, Sweden, Vol. 4, pp. 509-565.</p><p>Schaefer, V., Abramson, L.W., Hussin, J.D., and Sharp, K.D. (1997). “Ground improvement, Ground reinforcement, Ground treatment: Developments 1987-1997.” <em>Geotechnical Special Publication No. 69</em>,ASCE. ASCE, New York.</p></p>