<p><p><figure id='attachment_2586' style='max-width:1024px' class='caption aligncenter'><img class="wp-image-2586 size-large" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Graphic showing an embankment constructed on a weak soil foundation with a layer of reinforcement at the interface of the embankment and the foundation soils." width="1024" height="667" /><figcaption class='caption-text'> Embankment on Weak Foundation. (After Bonaparte and Christopher (1987)).</figcaption></figure><h2>Basic Function:</h2>Geosynthetic reinforced embankments stabilize embankments constructed on soft soils by means of horizontal layers of high-strength geosynthetics. The reinforcement placed at the base of the embankment and used to increase stability and resistance to foundation failures.<br><h2>Advantages:<em> </em></h2><ul> <li>Increase in the design global factor of safety, and height of the embankment</li> <li>Reduction or elimination of stabilizing side berms, thus reducing fill requirements</li> <li>Reduction in differential settlement</li> <li>Most general contractors can construct GREs and specialty contractors are not required</li></ul><h2>General Description:</h2>GREs utilize horizontal layers of high-strength geosynthetics to provide reinforcement under or near the base of embankments constructed on soft foundation soils. The geosynthetic can be a geotextile, geogrid, or a combination; the embankment is typically a granular material, although all soil types have been used. The reinforcement is used to increase stability and resistance to deep, rotational embankment foundation failures. The reinforcement does not reduce vertical settlement of the embankment, unless the reinforcement reduces the total volume of fill by permitting steeper side slopes. The reinforcement may help reduce differential vertical settlements. The reinforcement will likely reduce lateral displacement of the foundation soils.<br><h2>Geologic Applicability:</h2><ul> <li>Soft foundation soils, with no limitation on the depth of soft soils.</li> <li>Potential failure modes vary between shallow and deep, depending on the soft soil depth relative to embankment width.</li></ul><h2>Construction Methods:</h2>In geosynthetic reinforced embankment applications, a geosynthetic is typically placed on the ground surface or near the bottom of the embankment prior to placing the fill material. The geosynthetic can be a geotextile, geogrid, or a combination of a geotextile and a geogrid. A granular material is typically placed above the geosynthetic in specific patterns using lightweight construction equipment.<br><h2>Additional Information:</h2>Cost savings versus excavation and replacement, staged construction of fill, and preloading with prefabricated vertical drains are realized by eliminating or significantly reducing the number and/or duration of construction stages, and possibly through the use of steeper fill slopes to reduce the amount of embankment fill required to achieve planned grades. Thus, an embankment can be opened to construction traffic much sooner. Cost savings versus conventional unreinforced embankment can also be realized by reduced right-of-way requirements and less embankment fill material.<br><h2>SHRP2 Applications:</h2><ul> <li>New Embankment and Roadway Construction</li> <li>Roadway and Embankment Widening</li></ul><h2>Example Successful Applications:</h2><ul> <li>Westwego to Harvey Canal Levee, Louisiana</li></ul><h2>Complementary Technologies:</h2>Prefabricated vertical drains and fill preloading under appropriate project and subsurface conditions to reduce time to be able to use the embankment. Sand compaction piles in lieu of PVDs. Lightweight fills can also be used.<br><h2>Alternate Technologies:</h2>Excavation and replacement, prefabricated vertical drains and fill preloading, vacuum preloading with and without PVDs, deep dynamic compaction, vibrocompaction, lightweight fills, and column supported embankments.<br><h2>Potential Disadvantages:</h2>The total settlement magnitude will likely not be reduced. Detailed field observations are required during construction to monitor pore pressures and to maintain adequate safety factors. This technology is often combined with other special construction measures. When used alone, this technology is not appropriate for projects that cannot accommodate the time necessary for consolidation or for projects where total settlements must be reduced.<br><h2>Key References for this technology:</h2>Holtz, R.D., Christopher, B.R. and Berg, R.R. (2008). <em>Geosynthetic Design and Construction Guidelines</em>, U.S. Department of Transportation, Federal Highway Administration, National Highway Institute, Washington, D.C., FHWA-NHI-07-092.</p><p>Rowe, R.K. and Li, A.L. (2005). “Geosynthetic-reinforced embankments over soft foundations.” <em>Geosynthetics International</em>, Special Issue on the Giroud Lectures, 12, No. 1, 50-85.</p><p>Bonaparte, R. and Christopher, B.R. (1987). "Design and construction of reinforced embankments over weak foundations," <em>Reinforced Layered Systems, Transportation Research Record 1153</em>, Transportation Research Board, Washington, DC, 1987, 26-39.</p></p>