This should actually be listed in Marion County, TN...not Claiborne. This is in South Pittsburg, just off Hwy 72 near the "River Park" alongside the Tennessee River -- in the shadow of the Shelby Rhinehart Bridge. The tunnel formerly carried trackage for the Sequatchie Valley Railroad, which now follows a different route.
In the early 1900s the Southern Railway began to build its own railroad from Chattanooga to Stevenson, Alabama so they could avoid trackage rights on the Nashville, Chattanooga, and St. Louis Railroad. However, Southern abandoned the project due to a lack of funds. This bridge is one of the few remnants.