<p><p><figure id='attachment_3439' style='max-width:910px' class='caption aligncenter'><img class="wp-image-3439 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Location map for a geosynthetic reinforced embankment on the Westwego to Harvey Canal Levee, Louisiana." width="910" height="530" /><figcaption class='caption-text'> ©2010 Google – Map data</figcaption></figure></p><p><h2>Project Summary/Scope:</h2>A geogrid reinforced levee over soft soils was constructed with different types of geosynthetics between the towns of Westwego and Harvey, Louisiana. The total levee test section spans 274.5 meters of the mainline levee and is divided into three 91.5-meter reaches.</p><p>Subsurface Conditions: The soil profile consisted of 2.5-meter thick swamp deposits at the ground surface. The swamp deposits consist of soft to medium clays with some silt lenses and organics. Beneath the swamp deposits are interdistributary deposits that are approximately 3.5 meters thick and consist of soft to very soft clays containing some silts, organics, and shells. Prodelta deposits underlie interdistributary deposits and are approximately 6 meters thick. Prodelta deposits consist of massive clays of medium consistency with some silt. Groundwater was generally encountered at or above the ground surface.</p><p>The first reach contains a single layer of geotextile reinforcement with a tensile strength of 85 kN/m. The middle reach contains a single layer of uniaxial geogrid with a tensile strength of 85 kN/m. The last reach is a double layer reach containing 57 kN/m strength uniaxial geogrid panels (top) and 17.5 kN/m strength biaxial geogrid panels (bottom). The double layer geogrid panels were placed 0.75 meters apart. The test section levee had a base width of 38 meters. Flood side and protected side berms have slopes of 15 Horizontal:1 Vertical with the mainline levee having slopes of 3 Horizontal:1 Vertical.</p><p>This section was constructed in approximately 0.75 meters of standing water. The single layer geosynthetics were placed on a sand base. The double layer geosynthetics were placed at the bottom and top of the sand base. Semi-compacted fill was used to construct the embankment.<br><h2>Performance Monitoring:</h2>Geotechnical instrumentation consisted of settlement plates, piezometers, inclinometers, and strain gauges and extensometers for the geosynthetics. The embankment performed satisfactorily. Maximum strains for geotextile, single layer geogrid, and double layer geogrid were 3.6, 2.6, and 3.0%, respectively. Subsequent levee raising projects took into account strength gain of the foundation soils due to consolidation and remaining capacity of geosynthetic with a maximum design strain of 5%. Settlement data indicated minimal movements partially due to the lateral spread of the upper soft strata.<br><h2>Cost Information:</h2>Geotextile: Material – $3.82 per m2 for 74,239 m2 (in 1996 dollars)<br>Installation – $1.54 per m2 for 74,239 m2 Geogrid: Material – $8.78 per m2 for 74,239 m2 (in 1996 dollars)<br>Installation – $1.15 per m2 for 74,239 m2<br><h2>Case History Author/Submitter:</h2>Richard Varuso<br>Richard.J.Varuso@mvn02.usace.army.mil<br><h2>Project Technical Paper:</h2>Varuso, R.J., Grieshaber, J.B., and Mysore, S.N. (2005). “Geosynthetic reinforced levee section on soft normally consolidated clays.” Geotextiles and Geomembranes, 23, 362-383.<br><h2>Date Case History Prepared:</h2>November 2012</p></p>