Crumbling Earth: Tennessee uses military equipment to nail mountainside together to prevent a massive landslide

MAY 9, 2012 – TENNESSEE – TDOT has shut down all but one northbound lane of Interstate 75 between mile markers 141 and 144 in Campbell County. The earliest any southbound lanes will reopen is Thursday. The shut down comes because the embankment that collapsed beneath I-75 South on March 8 has now grown to threaten the median and northbound lanes. TDOT brought in the big gun to defend I-75 North by hiring an emergency repair contractor from Grand Junction, Colorado. “Myself and my crew got a call yesterday [Monday] and we arrived late last night,” said Nate Beard, vice president and engineer with Soil Nail Launcher, Inc. Beard’s crews will battle a beast of a mountainside with an oversized air gun originally built by the British military. “It is a big compressed air launcher that would launch nerve gas canisters up to seven miles,” said Beard. “It has been modified to launch soil nails, which is a 20 foot long, 1.5 inch diameter steel tube. We build that compressed air up to 3000 PSI, pull the trigger, and then it accelerates into the ground at 250 miles per hour.” In Campbell County, soil nail launcher crews are taking aim at a moving target. “The big challenge here is it is an actively moving landslide. I walked across this road at midnight and at 2:00 in the morning all of that material had fallen down to the bottom of the slope,” said Beard. “Our top priority is protecting the northbound lanes. We’ll launch around 300 soil nails.  We’ll put them in a really tight spacing. It works with the soil particles to confine them and create a beam effect, which then supports the interstate. It takes a lot of those loading and driving forces off the landslide.” Beard said crews should finish nailing the northbound lanes by Wednesday morning.  Then they will hammer away at the southbound lanes with even larger soil nails. “The south lanes can use nails that are 50 to 60 feet long and two inches in diameter,” said Beard. “You drive along these roads and they are perfect and they are flat, but they are on the edge of a cliff. A lot of people take that for granted, but the fact is there are frequently things like launched soil nails beneath the roads to keep them secure and stable.” –WBIR 10 News