During the spring of 2012, a large, deep-seated landslide threatened the southbound lanes of Interstate 75 near Jellico, TN. The Tennessee Department of Transportation’s geotechnical engineers designed a repair using a large rock buttress while recognizing the need for rapid temporary shoring during the project’s excavation phase. Based on the success of a similar repair less than five miles away, where over 500 launched soil nails were installed in less than four days, a similar temporary shoring plan was included in the project’s design.
During the excavation process, however, the prime contractor encountered an unexpected “trough” in the bedrock as well as significant subsurface water. These unforeseen site conditions led to a loss of soil retention and the massive failure of the interstate’s southbound lanes that literally developed overnight. The slide measured over 263 vertical feet from scarp to toe and was over an acre in area. During the failure’s initial phase, the slide moved more than one inch every two minutes.
The engineers from GeoStabilization International®, an industry leader in engineered soil repairs, were on-site within 12 hours of receiving the emergency call to assess the situation and quickly developed a design/build mitigation plan for landslide mitigation. Less than 24 hours after the initial failure, GeoStabilization’s crews and equipment (as well as a senior geologist) arrived at the site. During the initial 18-hour period of construction, using one of our soil stabilization innovations, the Soil Nail Launcher™, 258 launched soil nails prevented the regression of the headscarp into the remaining northbound lanes, and interstate traffic resumed.
Over the course of the following 26 days, GeoStabilization’s crews worked three (3) shifts to install over 6,500 SF of temporary slope stabilization that included launched soil nails, 11,510 feet of Self-Drilling SuperNail™ soil anchors, nearly 1,000 feet of 200,000-pound six-strand anchors up to 120 feet long each, and over 1,000-feet of horizontal drains. As the installation progressed, the slope’s factor of safety increased from less than 1.0 to 1.1 (with launched soil nails), to 1.3 (with self-drilling SuperNails™, and to 1.5 (with strand anchors). Despite the massive and unexpected initial failure, GeoStabilization’s emergency design/build solution enabled the general contractor to complete the overall buttress construction from almost catastrophic failure to six weeks ahead of the original construction schedule.
For over twenty years, our teams have been mitigating landslides and providing residential slope stabilization, slope monitoring, slope protection, and landslide prevention services. Contact GeoStabilization International® at 855-579-0536 to learn how to utilize our geohazard mitigation services for your geotechnical application.
If you are interested in a no-obligation site visit to determine if our services fit your geohazard mitigation needs, call us at 855-579-0536 or fill out our contact form.
