<p><p><h2>Preferred QC/QA Procedures</h2>There is no FHWA method for QC/QA.</p><p>Quality control is performed by monitoring the compaction energy per blow, the deflection of the soil per blow, the number of blows per compaction point, the total energy applied per compaction point, and the total settlement at a compaction point. An integrated monitoring system can show when optimal compaction is achieved (when additional blows will yield minimal improvement). Preliminary trials are an important aspect at each site to identify optimum site-specific compaction operations. Quality assurance can be accomplished by recording the before and after results to ensure that the desired average Standard Penetration Test (SPT) N-value or Cone Penetration Test (CPT) cone resistance is achieved for the zone needing improvement. Plate bearing tests for different field trials are also used to evaluate bearing characteristics and some in-situ geophysical tests have been suggested to overcome potential shortcomings of other in-situ tests.</p><p>Common Rapid Impact Compaction (RIC) practice utilizes in-situ penetration tests, usually the SPT, for quality assurance and the RIC’s on board computer for quality control. In most cases, SPTs are simply conducted before and after treatment to determine the effectiveness of the treatment. During compaction, the on-board computer provides real time data, which is used for quality control of the compaction process and of the equipment performance.</p><p>Currently, the QC/QA procedure for RIC is limited in terms of spatial coverage. Although in‑situ penetration tests provide good correlations for the magnitude and depth of improvement, adequate coverage of the improved area is difficult to attain unless a large number of tests are conducted.</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 rapid impact compaction are listed 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-2028'><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 >• SPT, CPT, plate bearing tests</td></tr><tr><td ><center>QC</td><td ><center>Process Control</td><td >• Monitoring compaction energy, surface deflection, number of tamper blows, drop high, drop weight</td></tr><tr><td ><center>QA</td><td ><center>Material Related</td><td >• SPT, CPT, plate bearing tests, geophysical</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-2032'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Parameters</td><td >• Density, stiffness/modulus, bearing capacity</td></tr><tr><td ><center>System Behavior</td><td >• Settlement</td></tr></tbody></table><br><h3>TABLE 3. EMERGING QC/QA PROCEDURES AND MEASUREMENT ITEMS</h3><table class='tablepress' id='tablepress-2033'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Related</td><td >• Integrated compaction monitoring system, intelligent compaction, geophysical methods</td></tr><tr><td ><center>Process Control</td><td >• None noted</td></tr></tbody></table></p></p>
<p><p><h2>QC/QA Guidelines</h2>There are currently no guidelines for conducting QC/QA testing for RIC, however RIC specialty contractors typically follow a similar QC/QA procedure.</p><p>Pre-improvement in-situ penetration tests, typically SPTs, are conducted on site. SPT N-values for the subsurface conditions of a site are usually extracted from a site investigation performed by an independent party.</p><p>During the “compaction trial” process performed by the specialty contractor (see the Design Guidance document for this technology), termination criteria for the compaction are determined. The termination criteria can include any values measured by the integrated monitoring system which indicate when optimum compaction has been achieved. Potential termination criteria include the deflection of the soil following the final blow delivered at a compaction point and the total settlement at a compaction point during compaction.</p><p>During the compaction phase, the following values are recorded for every compaction point:<br><ul> <li>Compaction point designation</li> <li>Date of compaction</li> <li>Time of compaction</li> <li>Total number of blows per compaction point</li> <li>Deflection of the soil (the set) following the final blow</li> <li>Total settlement</li> <li>Total energy applied</li> <li>Average drop height of the weight</li> <li>Termination criteria (one of four possible criteria):<br><ol> <li>Number of blows (typically 99)</li> <li>Total settlement</li> <li>A minimum set value (typically 5 mm/blow)</li> <li>Manual override (typically used at points underlain by incompressible material or cohesive layer that do not respond well to RIC)</li></ol></li></ul>Much of the QC data collected during compaction have more to do with process control and equipment performance, rather than the improvement of the unstable soil.</p><p>Following compaction, post-improvement SPTs are performed to determine whether adequate compaction to a sufficient depth had been achieved by RIC. Similar to the pre-improvement SPTs, the post-improvement SPTs are performed by an independent party.</p><p>Finally, a quality control summary is submitted to the owner.</p></p>
<p><p><h2>References</h2>Braithwaite, E.J and du Preez, R.W. (1997). “Rapid Impact Compaction in Southern Africa.” Proceedings of the Conference on Geology for Engineering, Urban Planning and the Environment. South African Institute of Engineering Geologists.</p><p>Building Research Establishment (2003). “Specifying Dynamic Compaction.” BRE Report 458, Garston, BRE Bookshop, UK.</p><p>Kristiansen, H. and Davies, M. (2003), “Results of Becker Penetration Testing, Chilliwack Fire Hall”, AMEC Earth & Environmental, Inc., Burnaby, B.C., Canada, 10p.</p><p>Kristiansen, H. and Davies, M. (2004), “Ground Improvement Using Rapid Impact Compaction”, Proceedings from the 13th World Conference on Earthquake Engineering, Vancouver, B.C., Canada, Paper No. 496.</p><p>SAICE (2006). “Innovative new ground improvement method used controlled dynamic compaction.” Civil Engineering, 14(5), 3-6.</p><p>Serridge, C.J. and Synac, O. (2006). “Application of the Rapid Impact Compaction (RIC) technique for risk mitigation in problematic soils.” Proceedings of IAEG2006, London, Paper No. 294.</p><p>Simpson, L.A., S.T. Jang, S.T., Ronan, C.E. and Splitter, L.M. (2008) “Liquefaction Potential Mitigation using Rapid Impact Compaction.” Proceedings of the Conference of Geotechnical Earthquake Engineering and Soil Dynamics IV, Sacramento, CA, Paper No. 181.</p></p>