<p><p><h2>Preferred QC/QA Procedures</h2>No document exists that is considered to provide a comprehensive and thorough description of implementing a QC/QA program for partial encapsulation of expansive or other problematic soils using geomembrane. A testing program depends on the primary design goal of the partial encapsulation project. Based on the design goal, the QC/QA process selects different testing methods. The QC/ QA process includes different geophysical techniques, such as Ground Penetration Radar (GPR), Time Domain Reflectometer (TDR), Falling Weight Deflectometer (FWD), or Light Falling Weight Deflectometer (LFWD), field density and CBR tests, level surveys, Benkelman beam test, and strain measurement, etc. from the beginning to the end of the service period of the partial encapsulation project. The selection of a testing program is influenced by other factors, such as method of construction, site condition, type of road, climatic condition, and time and quality of construction, etc.</p></p>
<p><p><h2>QC/QA Guidelines</h2>The determination of moisture variation in pavement layers and subgrade at different time periods from the construction phase to the end of the design life is necessary to evaluate the effectiveness of the partial encapsulation technique.<br><ol> <li>Duringconstruction, the optimum moisture content and maximum dry density of the soil can be determined by the ASTM or AASHTO standards. These parameters can be monitored by sand cone test and/or nuclear gauge measurement. Field CBR test can be conducted at the surface and mid-depth of the fill (Sale et al. 1973, Smith and Pazsint 1975, Smith 1979, and Steinberg 1998).</li> <li>After the construction of the pavement layers, different techniques, such as level survey, Benkelman beam test, strain measurement, etc. can be used to evaluate the effect of moisture content on the performance of the pavement layers and subgrade throughout the service period.</li> <li>Different geophysical techniques, such as Ground Penetration Radar (GPR), Time Domain Reflectometer (TDR), Falling Weight Deflectometer (FWD), or Light Falling Weight Deflectometer (LFWD) are preferred to evaluate the pavement layers and subgrade before, during, and after construction.</li></ol>These QC/QA techniques have standard ASTM or AASHTO testing procedures. Contractor experience with similar partial encapsulation projects is important for ensuring quality construction. Laboratory tests should be carried out to evaluate the properties of the pavement layers to ensure the use of quality materials in the construction.</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 partial encapsulation 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-2024'><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 >• Field density and moisture content of soil, properties of geomembrane samples</td></tr><tr><td ><center>QC</td><td ><center>Process Control</td><td >• Compaction equipment, lift thickness, number of passes, protection of geomembrane, geomembrane welding and repair if damaged</td></tr><tr><td ><center>QA</td><td ><center>Material Related</td><td >• Sand cone, nuclear gauge measurement, CBR, variation of moisture content with time</td></tr><tr><td ><center>QA</td><td ><center>Process Control</td><td >• Level survey, Benkelman beam test, soil strain measurement, effectiveness of geomembrane welding</td></tr></tbody></table><br><h3>TABLE 2. PERFORMANCE CRITERIA USE IN QC/QA MONITORING PROGRAMS</h3><table class='tablepress' id='tablepress-2025'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Parameters</td><td >• Field density, moisture content</td></tr><tr><td ><center>System Behavior</td><td >• Variation of moisture content, pavement surface heave, pavement roughness, pavement cracks</td></tr></tbody></table><br><h3>TABLE 3. EMERGING QC/QA PROCEDURES AND MEASUREMENT ITEMS</h3><table class='tablepress' id='tablepress-2027'><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>References</h2>Christopher, B.R., Schwartz, C., and Boudreau, R. (2010). <em>Geotechnical Aspects of Pavements – Reference Manual</em>. FHWA NHI-10-092, National Highway Institute, 568p.</p><p>Eaton, R. A., and Berg, R. L. (1980). “New Hampshire field studies of membrane encapsulated soil layers with additives.” <em>CRREL Special Report (US Army Cold Regions Research and Engineering Laboratory) </em>(80-33).</p><p>Elseifi, M. (2003). <em>Performance Quantification of Interlayer Systems in Flexible Pavements using Finite Element Analysis, Instrument Response, and Non destructive Testing</em>, Ph.D. Dissertation submitted to the Faculty of the Virginia Polytechnic Institute and State University, USA.</p><p>Koerner, R. M. (1998). <em>Designing with Geosynthetics</em>, 4th Ed., Prentice Hall, Upper Saddle River, N.J, 783p.</p><p>Picornell-Darder, M. (1985). <em>The development of Design Criteria of Select the Depth of a Vertical </em><em>Moisture Barrier (Volume I-III) (Expansive soils),</em> Ph.D. Dissertation submitted to the Faculty of the Texas A&M University, USA.</p><p>Rankilor, P. R. (1981). <em>Membranes in Ground Engineering</em>, John Wiley & Sons, Inc., London England, 377p.</p><p>Sale, J. P., Parker Jr, F., and Barker, W. R. (1973). “Membrane encapsulated soil layers.” <em>American Society of Civil Engineers, Journal of the Soil Mechanics and Foundations Division</em>, 99(SM12), 1077-1108.</p><p>Smith, N. (1979). “Construction and performance of membrane encapsulated soil layers in Alaska.” <em>CRREL Report (US Army Cold Regions Research and Engineering Laboratory) </em>(79-16).</p><p>Smith, N., and Pazsint, D. A. (1975). “Field test of a MESL (Membrane-Enveloped Soil Layer) road selection in central Alaska.” <em>United States Army, Corps of Engineers, Cold Regions Research & Engineering Laboratory, Hanover, N.H. Technical Report </em>(260).</p><p>Steinberg, M. L. (1998). <em>Geomembranes and the Control of Expansive Soils in Construction</em>, McGraw-Hill, New York, 222p.</p></p>