<p><p><figure id='attachment_2622' style='max-width:650px' class='caption aligncenter'><img class="wp-image-2622 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic diagram showing reinforcement in a slope. Both long strips for slope stability and short strips for compaction aid are shown." width="650" height="320" /><figcaption class='caption-text'> Slope Reinforcement using Geosynthetics (Figure from Christopher et al. 1990)</figcaption></figure><h2>Basic Function</h2>Reinforced soil consists of soil reinforcements added to natural soil body alternating with compaction efforts applied to form a composite which containing a improved strength and stability versus the initial soil state.<br><h2>Advantages:</h2><ul> <li>Uses simple and rapid construction procedures</li> <li> Eliminate wall facing elements</li> <li>Less required right of way</li> <li>Less filling materials or ROW than flatter, unreinforced slopes</li> <li>Vegetated-faced soil slopes landscaped to blend with natural environment</li></ul><h2>General Description:</h2>Reinforced Soil Slopes (RSSs) are a form of mechanically stabilized earth that incorporates planar reinforcing elements in constructed earth-sloped structures with face inclinations less than 70º from the horizontal (MSE structures with face inclinations &gt; 70º are classified as walls). Multiple layers of geogrids, geotextiles, steel welded wire mats, or woven steel mats may be placed in an earthfill slope during construction to reinforce the soil and provide a stable, sloped faced earth retention structure, as shown in Figure above.<br><h2>Geologic Applicability:</h2><ul> <li>RSSs can be constructed over any firm foundation or pre-treated subgrade surface, which shall be level, uniform, and also free from deleterious materials, loose and/or otherwise unsuitable soils.</li> <li> Any soft areas as predetermined by engineers shall be excavated or replaced with suitable compacted soils.</li></ul><h2>Construction Methods:</h2>The construction of RSSs is very similar to normal slope construction. First, site preparation should be conducted to treat the subgrade soil prior to the first level of reinforcement placement. Second, in reinforcement layer placement stage, the reinforcement shall be well secured by retaining pins to prevent movement from filling and compaction process. Third, the well-designed backfill soil shall be placed on the top of flatted reinforcement to form a lift with minimum thickness of 6 inches. Fourth, compaction should be applied on placed backfill layer to achieve designed compacted density and moisture content. Step two to Step<br>four are repeated until the desired slope height is reached. Then, the surface drainage features and slope treatment are added at completion of the reinforced slope.<br><h2>Additional Information:</h2>Mechanically stabilized earth slopes, i.e. RSSs, have been used by state highway agencies since the early 1980s. The use of RSS structures has expanded dramatically in the last two decades, and it is estimated that several hundred RSS structures have been constructed in the United States. Currently, 100 to 150 RSS projects are being constructed yearly in connection with transportation related projects in the United States, with an estimated projected vertical face area of 2,000,000 ft2/year (190,000 m2/year). Significantly more RSS projects are designed and constructed yearly for private (non-transportation) works.<br><h2>SHRP2 Applications:</h2><ul> <li>Embankment and roadway construction over unstable soils</li> <li>Roadway and embankment widening</li></ul><h2>Example Successful Applications:</h2><ul> <li>The Dickey Lake Roadway Grade Improvement Project – Northern Montana</li> <li>Salmon-Lost Trail Roadway Widening Project – Idaho</li> <li>Pennsylvania SR 54 Roadway Repair Project – Pennsylvania</li></ul><h2>Complementary Technologies:</h2>RSS can be used with Column Supported Embankments and MSE walls<br><h2>Alternate Technologies:</h2>MSE walls, conventional unreinforced slopes<br><h2>Potential Disadvantages:</h2><ul> <li>Generally limited to firm foundation sites.</li> <li>Relatively large space needed to install required reinforcement.</li> <li>Project specific or regionally specific erosion control design and detailing for steepened slope face</li></ul><h2>Key References for this Fact Sheet:</h2>Berg, R.R, Christopher, B.R, and Samtani, N.C (2009). Design of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes, U.S. Department of Transportation, Federal Highway Administration, Washington, D.C., FHWANHI-09-083, 622 p.</p><p>Christopher, B.R., Gill, S.A., Giroud, J.P., Juran, I. Scholsser, F., Mitchell, J.K. and Dunnicliff, J., (1990). “Reinforced Soil Structures, Volume I. Design and Construction Guidelines”,U.S. Department of Transportation, Federal Highway Administration, Washington DC, Report No. FHWARD--89-043,287 p</p></p>