Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85910
Road into Bridge A massive landslide causes Tennessee DOT to rethink its rebuilding S By Tina Grady Barbaccia ometimes itʼs just better to start over. That's exactly how the Tennessee Department of Transportation (TDOT) decided to handle the collapse of a nearly three-mile stretch of State Route 7 in Maury County after a huge landslide following devastating flooding. Faced with a daunting rebuilding, TDOT dra- matically changed course. Heavy rains saturated the ground underneath the pavement, causing two sections of the roadway to collapse and slide down a steep embankment, closing the roadway for several months. The ex- treme weather and flooding struck southern middle Tennessee April 30 to May 2, 2010. The stretch of State Route 7 located in the Santa Fe community in the northwest section of Maury County was shut down while a concrete deck bridge was built over the crumbled roadway. Following the landslide, TDOT determined that constructing a bridge over the damaged section of roadway would be more cost-effective than recon- structing the area. began in early 2011, and the ribbon-cutting for the bridge was Nov. 30, 2011. TDOT Commissioner John Schroer says that "this was the most extensive repair project initiated by TDOT after the May 2010 floods." A Sinking Road So, TDOT built a 684.5-foot-long, 62-foot-wide, three-lane, five-span bridge. The project had a total of 338,580 cubic yards of road and drainage exca- vation, and 547,502 pounds of steel bar reinforce- ment was used. The bridge work used 2,257 cubic yards Class of A, D and S concrete. The concrete girder deck bridge first had to be designed, and was then let to contract in Decem- ber 2010. Construction on the $9.5-million project The two landslide areas involved nearly 1,500 feet of roadway. In some places, the road sank 20 feet below its original elevation, prompting TDOT to ini- tiate an emergency contract for geotechnical studies of the soil in the area and for the design of the re- pairs. "It's rare to see a landslide of this magnitude," says TDOT geotechnical engineer Vanessa Bateman. Before action was taken to begin stabilization of the soil or any repair decisions were made, Bate- man noted that "any subsequent wet weather could trigger more slides in this area and could further complicate repair efforts. The ground remains ex- tremely unstable." TDOT chief engineer Paul Degges refers to the rain as "a thousand-year rainfall – a very improb- able event. Our average annual rainfall is 45 inches." Degges says that although the state highway trans- portation system fared well – no bridges washed Better Roads February 2012 37