<p><p><figure id='attachment_3569' style='max-width:1024px' class='caption aligncenter'><img class="wp-image-3569 size-large" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of a reinforced soil slope after construction and partially vegetated." width="1024" height="768" /><figcaption class='caption-text'> Completed RSS partially vegetated. (Photograph courtesy of Rich Barrows, FHWA)</figcaption></figure></p><p><div><h2>Project Summary/Scope:</h2>As part of a highway widening project in Idaho, the FHWA Western Federal Lands Highway Division designed and supervised the construction of a 565-foot long, 50-foot high (172-meter long, 15.3-meter high) permanent geosynthetic-reinforced slope to compare its performance with other types of retaining structures along the alignment. Widening of the original road was a achieved by turning the original 2H:1V unreinforced slope into a 1H:1V reinforced slope. Aesthetics was an important consideration in the selection of the retaining structures along scenic Highway 93. A vegetated facing was, therefore, used for the reinforced slope section. On-site soil consisting of decomposed granite was used as the reinforced fill.</p><p>The geotextile-reinforced slope was designed in accordance with the FHWA guidelines. The final design consisted of two reinforced zones with a constant reinforcement spacing of 1 foot (0.3 meters). The reinforcement in the lower zone had an ultimate tensile strength of 6,850 lb/ft (100 kN/m), and the reinforcement in the upper zone had based on partial reduction factors. Field tests were used to reduce the installation damage reduction factor from the assumed value of 2.0 to the project-specific test value of 1.1, and provided substantial savings to the project (40% reduction in reinforcement required).</p><p><figure id='attachment_3571' style='max-width:674px' class='caption aligncenter'><img class="wp-image-3571 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of a reinforced soil slope during construction." width="674" height="485" /><figcaption class='caption-text'> During construction. Photograph courtesy of Rich Barrows, FHWA)</figcaption></figure></p><p><figure id='attachment_3572' style='max-width:670px' class='caption aligncenter'><img class="wp-image-3572 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of a reinforced soil slope during construction with an erosion mat on slope face." width="670" height="480" /><figcaption class='caption-text'> During construction, with erosion mat on face (Photograph courtesy of Rich Barrows, FHWA)</figcaption></figure><h2>Alternate Technologies:</h2>MSE walls were used in other portions of the project. Costs of the MSE walls were on the order of $22/ft² ($240/m²) of vertical face for similar or lower height structures, which is approximately 47% greater than the RSS structure.<br><h2>Cost Information:</h2>The steepened reinforced slope was constructed at a faster rate and proved more economical than the other retaining structures constructed along the same alignment. The constructed cost of the reinforced slope section was on the order of $15/ft² ($160/m²) of vertical face.<br><h2>Project Technical Paper:</h2>Zornberg J., Barrows, R., Christopher, B.R. and Wayne, M. (1995). "Construction and Instrumentation of a Highway Slope Reinforced with High-Strength Geotextiles", <em>Proceedings of Geosynthetics '95</em>, Nashville, TN.<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div></p></p>