<p><p><h2>Preferred QC/QA Procedures</h2>The Federal Highway Administration (FHWA) document <em>Geosynthetic Design and Construction Guidelines</em> provides standard specifications for geosynthetics used to stabilize subgrade and includes preferred QC/QA procedures. The document is summarized below.</p><p><table class='tablepress' id='tablepress-1964'><thead><th><center>Publication Title</th><th><center>Publication
Year
</th><th><center>Publication Number</th><th><center>Available for Download</th></thead><tbody><tr><td ><center>Geosynthetic Design and Construction Guidelines</td><td > <center>2008</td><td > <center>FHWA NHI-07-092</td><td > <center>No<sup>1</td></tr></tbody></table><br><p class="disclaimer"><sup>1</sup> <a href="http://www.nhi.fhwa.dot.gov/training/nhistore.aspx">http://www.nhi.fhwa… are many QC/QA methods necessary to ensure proper construction of geosynthetic-reinforced construction platforms. The proper methods will be dependent on the design methods, existing conditions, and desired performance. The majority of the QC/QA procedures are non-proprietary tests well defined by ASTM and AASHTO.</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 Geosynthetic Reinforced Working Platforms 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><strong>TABLE 1. TYPICAL EXISTING QC/QA PROCEDURES AND MEASUREMENT ITEMS</strong></h3><table class='tablepress' id='tablepress-1965'><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 >•Base course and subgrade: CBR, undrained shear strength, compaction curve, permeability, moisture content, Atterberg limits, and soil classification, and grain size distribution
•Geosynthetic properties: mass per unit area, apparent opening size, aperture size, tensile strength, tensile stiffness, burst resistance, puncture resistance, tear strength, overlap efficiency, interface shear strength, UV resistance, permittivity, and permeability
</td></tr><tr><td ><center>QC</td><td ><center>Process Control</td><td >•Number of lifts, rolling pattern and passes for compaction, width of geosynthetic overlap and seam, preconditioning
</td></tr><tr><td ><center>QA</td><td ><center>Material Related</td><td >•Sand cone density test, specific gravity measurements, CBR test, vane shear measurements (Pilcon)
</td></tr><tr><td ><center>QA</td><td ><center>Process Control</td><td >•CBR measurements (CBR penetrometer), static and dynamic plate load tests, a Dynamic Falling Weight Deflectometer (FWD), trafficking tests, the overall dynamic compaction control and the profile measurements (ruts), field observations</td></tr></tbody></table><br><h3><strong>TABLE 2. PERFORMANCE CRITERIA USE IN QC/QA MONITORING PROGRAMS </strong></h3><table class='tablepress' id='tablepress-1966'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Parameters</td><td >•CBR, relative compaction
</td></tr><tr><td ><center>System Behavior</td><td >•Traffic Benefit Ratio (TBR), composite modulus, bearing capacity, rut depth, stress distribution angle, Base Course Reduction factor (BCR), roughness</td></tr></tbody></table><br><h3><strong>TABLE 3. EMERGING QC/QA PROCEDURES AND MEASUREMENT ITEMS</strong></h3><table class='tablepress' id='tablepress-1967'><thead><th><center>Topics</th><th><center>Items</th></thead><tbody><tr><td ><center>Material Related</td><td >•ASTM standard test methods for properties of base course, subgrade, and geosynthetics, Sand cone density test, and CBR tests</td></tr><tr><td ><center>Process Control</td><td >•Plate load test, trafficking test, and FWD test, Compaction, field observation, overlap and seaming of geosynthetics</td></tr></tbody></table></p></p>
<p><p><h2>QC/QA Guidelines</h2>A geosynthetic-reinforced construction platform requires the use of multiple design steps and construction methods. Because of the number of design steps, the QC/QA procedures for geosynthetic-reinforcement in pavement systems can be numerous and vary greatly depending on the existing conditions and design criteria. Each layer of the pavement system (subgrade, subbase, and base course), must be tested and monitored to ensure that the specified design criteria and inputs are met.</p><p>In addition to monitoring the soil in unreinforced and reinforced conditions, the geosynthetics in a reinforced condition must also be monitored. The QC/QA procedures of geosynthetics include testing for the geosynthetic properties, such as tensile tests, puncture tests, apparent opening size, and mass per unit area. Monitoring installation procedures of the geosynthetic on the project is also required.</p><p>Geosynthetic Design and Construction Guidelines (Holtz et al., 2008) provides standard specifications for the geosynthetics used to stabilize subgrade and can be used for QC/QA purpose. Holtz et al. (2008) suggests that the field personnel must be responsible for the appropriate installation of the geosynthetics and should be able to check the required properties and survivability requirements of the geosynthetics delivered to the site. Pavement performance evaluation and layered elastic analysis are used for quality assurance. Verification of material properties is used for both quality control and quality assurance. KDOT provides standard specifications for materials used in construction working platform applications and thus can be used for QC/QA purposes (www.ksdot.org/burconsmain/specprov/2007/pdf/07-17004.pdf)<em>.</em> Layered elastic analysis is used to quantify and evaluate the structural contribution of reinforced granular working platforms used for constructing highway pavements over soft subgrade. The effect of geosynthetics was expressed in terms of the reinforcement factor (Kim et al., 2005). The performance of test sections was evaluated from measurements of rut depth and base course layer thickness in the channelized wheel path, cross-sectional profile of the road surface and the deformed geosynthetic, and strain in the geosynthetic, with a cumulative number of vehicle passes (Fannin and Sigurdsson, 1996).</p><p>Currently, the QC/QA procedure for geosynthetic-reinforced construction platforms is adequate for haul roads, storage areas, and embankment support, but is somewhat inadequate for permanent roadways. Additional research into QC/QA procedures is advised in order to allow for a better evaluation for this technology when used in conjunction with paved roads. The potential use of other QC/QA tests should be investigated.</p><p>Because the QC/QA procedures are so broad in nature there are many new techniques being developed and adopted. New techniques include CBR measurements (CBR penetrometer), vane shear measurements (Pilcon), specific gravity measurements, static and dynamic plate load tests, a dynamic Falling Weight Deflectometer (FWD), etc.</p></p>
<p><p><h2>References</h2>Dawson, A.R. and Little, P.H. (1990). “Reinforced haul-roads: Trials at Bothennar, Scotland.” <em>Proceedings of the fourth International Conference on Geotextile, Geomembranes and Related Products, </em>May 28- June 1, 250p.</p><p>Fannin, R.J. and Sigurdsson, O. (1996). “Field observations on stabilization of unpaved roads with geosynthetics.” <em>Journal of Geotechnical Engineering,</em> Vol. 122, No. 7, 544-553.</p><p>Holtz, R.D., Christopher, B.R., and Berg, R.R. (2008). <em>Geosynthetic Design and Construction Guidelines</em>, U.S. DOT, Federal Highway Administration, Washington, DC, FHWA-HI-07-092, 460p.</p><p>Kansas Department of Transportation (KDOT). (2007). “Special provision to the standard specifications.”</p><p>Kim, W., Edil, T.D., Benson, C.H., and Tanyu, B.F. (2005). “Structural contribution of geosynthetic-reinforced working platforms in flexible pavement.” <em>Transportation research Record 1936,</em> National Research Council, 43-50.</p><p>Hufenus, R., Rueegger, R., Banjac, R., Mayor, P., Springman, S.M., and Bronnimann, R. (2006). “Full-scale field tests on geosynthetic reinforced unpaved roads on soft subgrade.” <em>Geotextiles and Geomembranes,</em> Vol. 24, No. 1, 21-37.</p><p>Yong, K.Y., Chan, S.F., and Lee, K.K. (1990). “Reinforced soil working platform for offshore jacket fabricated yard.” <em>Proceedings of the 4<sup>th</sup> International Conference on Geotextiles, Geomembranes and Related Products,</em> 223-226.</p></p>