<p><p><figure id='attachment_3519' style='max-width:840px' class='caption aligncenter'><img class="wp-image-3519 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the construction of a mechanically stabilized earth wall on the Crosstown Project in Minneapolis Minnesota." width="840" height="627" /><figcaption class='caption-text'> Construction of a MSE wall on Crosstown proejct. (Photo courtesy of Ryan Berg)</figcaption></figure></p><p><h2>Project Summary/Scope:</h2>MSE walls were used extensively on the Crosstown Project located in Minneapolis, Minnesota. The walls were used to widen existing roadways, construct new ramps, and construct new bridge approaches. The project enlarged and streamlined the I-35W and Minnesota Highway 62 interchange. This is a heavily traveled roadway in a congested urban area. Several bridges were widened and several new bridges were constructed as part of this project. The detailed wall designs and the wall components were supplied by a Minnesota Department of Transportation (MnDOT)pre-approved MSE wall vendor. Design followed the ASD method (AASHTO 17th Edition 2002). Most of the walls were constructed during the 2008 and 2009 construction seasons.</p><p>Approximately 300,000 ft² (28,000 m²) of MSE walls were constructed in 24 separate walls. Typical wall heights were approximately 25 to 30 feet (7.5 to 9 meters), and the maximum wall height was 45 feet (14 m). The MSE walls were faced with architectural segmental precast panels and reinforced with steel bar mats. Facing panels were painted after wall construction.</p><p>The reinforced wall fill was an angular, well-graded sand. The walls were designed for a 100-year life. Many walls had traffic barriers on top of the reinforced zones. The barriers were designed by the MnDOT project design consultant. A geomembrane was specified and installed across the top of the reinforced zones to prevent or minimize infiltration of de-icing salt runoff into the reinforced fill.</p><p>Temporary Welded Wire Mesh (WWM) faced walls were also used on this project for temporary bridge abutments (see Figure 2-2), bridge approach embankments, and construction staging. These walls were also designed and supplied by the same MnDOT pre-approved vendor.</p><p>The use of MSE walls on this project provided a relatively rapid means of wall construction and produced structures designed for a 100-year life.<br><h2>Complementary Technologies Used:</h2>Geosynthetics in Pavement Drainage: a geomembrane was used above the reinforced fill (beneath the pavement) to minimize inflow of deicing salt laden runoff water.<br><h2>Alternate Technologies:</h2>Cast-in-place, concrete cantilever walls were also extensively used on this project. Approximately 500,000 ft² (49,000 m²) of CIP walls were constructed.<br><h2>Cost Information:</h2>The cost of these MSE walls was $30.50 per ft² ($330 per m²) of face area, plus $17 per yd³ ($20 per m³) for the reinforced wall fill and $375 per yd³ ($450 per m³) of concrete for the traffic barrier moment slab. MSE wall cost with the select granular wall fill and moment slab was approximately $54.50 per ft² ($585 per m²) of face area. The MSE wall costs do not include the traffic barrier and noise wall. The cost of the cast-in-place walls on the project was $67.20 per ft² ($723 per m²)of face area plus cost of backfill, for an approximate total cost of $76 per ft² ($820 per m²) of face area.<br><h2>Project Technical Paper:</h2>Berg, R.R., Christopher, B.R. and Samtani, N.C., Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes, FHWA NHI10-024 Vol I, U.S. DOT, Federal Highway Administration, Washington, D.C., 2009, pp 306.<br><h2>Date Case History Prepared:</h2>November 2012</p></p>