<p><p><figure id='attachment_2582' style='max-width:1025px' class='caption aligncenter'><img class="wp-image-2582 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…
" alt="Photograph showing a geosynthetic reinforced temporary unpaved road. Placement of geosynthetic in roadway to the right." width="1025" height="380" /><figcaption class='caption-text'> Temporary and unpaved roads (left, Courtesy of NHI) Placement of geosynthetic in roadway (right, Courtesy of Kansas Department of Transportation)</figcaption></figure><h2>Basic Function:</h2>Geosynthetics are used as reinforcements in granular fill to form a temporary construction platform to support construction equipment and traffic over soft soil in order to avoid the formation of mud waves and excessive ruts. The contribution of the geosynthetic layer is to increase the local bearing capacity of soft subgrade.<br><h2>Advantages:<em> </em></h2><ul> <li>Advantages include its suitability for rapid renewal of transportation facilities, minimizing disruption of traffic.</li> <li>Suitable for rapid renewal of transportation facilities.</li> <li>Minimize disruption of traffic.</li> <li>Reduce the risk of subgrade support problems<strong>.</strong></li> <li>Geosynthetics are not significantly affected by moisture.</li> <li>Produce long-lived facilities for soft soil.</li> <li>More economical than pile supported platforms for soft soil.</li></ul><h2>General Description:</h2>Design of geosynthetic-reinforced construction platforms is commonly based on local bearing capacity or slope stability. The contribution of the geosynthetic layer is to increase the local bearing capacity of soft subgrade. Several researchers have suggested different bearing capacity factors, N<sub>c</sub>, for unreinforced, geotextile, and geogrid-reinforced unpaved roads. A single layer of geosynthetic is commonly used for unpaved roads.<br><h2>Geologic Applicability:</h2><ul> <li>Geosynthetic-reinforced construction platforms may be used for soft subgrade with California Bearing Ratio (CBR) less than 3.</li> <li>Geosynthetics are used as reinforcements in granular fill to form a temporary construction platform to support construction equipment and traffic over soft soil in order to avoid the formation of mud waves and excessive ruts.</li></ul><h2>Construction Methods:</h2>Surface of the subgrade was leveled to the targeted elevation and geosynthetics are laid directly on the subgrade soil in the machine direction parallel to the direction of trafficking with the required overlap and seamed as specified in the specification document. Drainage ditches are dug along each side of the road to provide drainage facility. The base course is placed in lifts and compacted to required degree of compaction at specified moisture content to provide desired grade.<br><h2>Additional Information:</h2>A single layer of geosynthetic is commonly used for unpaved roads. Slope stability analysis is generally adopted to evaluate the safety of heavy construction equipment (such as cranes) operated on soft soil. Current design methods for geosynthetic-reinforced unpaved roads are based on a single reinforcement layer placed at the interface between subbase and subgrade. In practice, however, multiple layers of geosynthetics are sometimes used. Development of design methods for multiple layer geosynthetic-reinforced unpaved roads is needed. Two-dimensional limit equilibrium methods are commonly used for designing geosynthetic-reinforced working platforms under heavy construction equipment. However, actual field conditions are most likely a three-dimensional problem.<br><h2>SHRP2 Applications:</h2><ul> <li>New Embankment and Roadway Construction over Unstable Soils</li> <li>Roadway and Embankment Widening</li> <li>Stabilization of Pavement Working Platforms</li></ul><h2>Example Successful Applications:</h2><ul> <li>Stabilization of unpaved roads with geosynthetics, Vancouver, British Columbia</li> <li>Reinforced haul-roads: Trials at Bothkennar, Scotland</li> <li>Reinforced road base, Monroe, LA</li></ul><h2>Alternate Technologies:</h2>Chemical stabilization soil, Excavation and Replacement, Use of high-quality pavement materials, Geotextiles with geogrid, Pile supported platforms.<br><h2>Potential Disadvantages:</h2><ul> <li>Lack of an acceptable method to evaluate the difference between geosynthetic products and to design multiple layers of geosynthetics.</li> <li>Lack of a reliable AASHTO design method</li> <li>Lack of demonstration of life cycle cost benefits</li></ul><h2>Key References for this technology:</h2>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). “Geosynthetic design and construction guidelines.” U.S. Department of Transportation, Federal Highway Administration, Washington, D.C., FHWA-HI-07-092.</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>
