<p><p><figure id='attachment_2791' style='max-width:1024px' class='caption alignnone'><img class="wp-image-2791 size-large" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph showing the installation of ground anchors to stabilize a loess bluff prior to installation of a mechanically stabilized earth wall." width="1024" height="683" /><figcaption class='caption-text'> Installation of ground anchors to stabilize the Mississippi loess. Photograph from Kenneth Bergeron; from Fair-weather, 1997.</figcaption></figure></p><p><div><h2>Project Summary/Scope:</h2>Severely eroded slopes were threatening the stability of a row of houses. The general area is prone to bluff erosion, but in more recent times the problem has become increasingly worse. This resulted not only in property loss, but a slide had caused two deaths in 1980. A probable cause of this erosion was a redirection of the Mississippi river in an effort to straighten it. The project consisted of 105 soldier piles, 60 conventional ground anchors, 105 Single Bore Multiple Anchors (SBMAs), 550 soil nails, and an MSE wall.</p><p>Subsurface Conditions: The soil in the area consists of windblown silt commonly referred to as loess. Geologists estimated landslides had been occurring in the area for centuries.</p><p>The lower wall was 850 feet long, 32 feet high, and 6 feet off the road. It consisted of 105 soldier piles up to 45 feet in length, 40 SBMA’s 65 feet long, and 60 conventional 65-foot long ground anchors. Ten of the lower wall SBMAs had a capacity of 140 kips and 30 had a capacity of 75 kips. The upper wall was 62 feet tall and 450 feet long. It was reinforced with 550 soil nails (with lengths ranging from 30 to 55 feet) and 65 SBMAs (110 feet long with a capacity of 150 kips). The decision was made to extend the yards of the houses on the edge of the bluff. An SMSE wall system was used to create this extension. The MSE wall extended over 270 feet of the upper soil nail wall, was 20 feet deep, and ranged from heights of 26 to 30 feet. The area was stabilized using a geogrid soil reinforcement system and 6,000 lbs. of lightweight aggregate. A segmental lock unit interlocking system was used as the facing.</p><p>The lower wall was constructed first, followed by the upper wall. In order to complete the upper wall with the SMSE wall system, a wire form faced temporary wall was installed. This was because the segmental block retaining wall required bottom-up construction while the soil nail wall was a top-down process.<br><h2>Complementary Technologies Used:</h2>Steel soldier piles, conventional ground anchors, Single Bore Multiple Anchors (SBMAs), soil nails, and MSE wall<br><h2>Performance Monitoring:</h2>One monitoring method was load testing. Some testing showed capacity below the specifications, but this was accepted because the loads were still well above design strength.</p><p>A 15-foot deep crack appeared in the upper section of the lower wall when completing the last four top-down lifts. In the design, a temporary stress condition imposed by construction was overlooked. Crane mats and timber beams were put in place underneath the cracking section to provide temporary support. Temporary shotcrete was applied to the wall and a permanent 30-inch, square shotcrete footing reinforced with rebar was put in place to stabilize the area. Once in place, the nails were not found to be overstressed. Once the wall was completed the excess shotcrete was chipped away and the permanent facing was installed.</p><p>In the upper wall, some of the <em>tubes a manchette </em>installed with the SBMAs had to be grouted for the entire 110 feet.<br><h2>Cost Information:</h2>The lightweight fill cost a little over $30 per cubic yard. The first problem encountered cost $100,000 to remediate. The overall project was given a funding of $5.3 million and the contractor was able to complete the project with $4 million.<br><h2>Project Technical Paper:<strong> </strong></h2>Fairweather, V. (1997) "Saving the Bluffs: Engineering on the Edge." Civil Engineering, ASCE, December issue, pp. 37-40.<br><h2>Date Case History Prepared:</h2>November 2012</p><p>&nbsp;</p><p></div></p></p>