Part of a hill gave way and boulders fell on to the highway.
The rockslide occurred at Mile Marker 142.
A southbound detour has been set up at Exit 160 (Jellico).
Follow US 25W / SR 297 West to SR 63 South, and then re-enter I-75 South.
Motorists heading north can take Exit 13 (Caryville/Jacksboro/LaFollette).
Follow US 25W north to LaFollette, continuing to Jellico, and then re-enter I-75 North.
There are separate detours for wide-loads.
The good news is that I-75 southbound lanes are expected to reopen on or before March 17 – a little late for March Breakers but not for late Snowbirds - and one lane on the northbound side is expected to reopen on or before March 24.
The entire repair project is scheduled to be complete on or before April 15.
TDOT says southbound travellers should add 40 minutes to their trips whole northbound travellers 45 minutes.
But anecdotal and media reports indicate the detours could take substantially longer, also depending on rush hour traffic.
Atlanta’s Channel 11 quoted a local resident who said the detours can be a pain.
David Perkins of Pioneer, Tenn., along route 297 - the southbound detour – called traffic a headache.
"Probably five or six miles back there it's just bumper to bumper," he said.
While downtown roads in Jacksboro and LaFollette on the northbound detour are crowded, driving can get dangerous once the routes narrow to two lanes.
"You know, the trucks can't get through the sharp turns on 297,” Perkins said.
“And then when you've got two side by side, one has to stop and let four or five through and you're sitting there for quite awhile."
TDOT spokesman John Schroer said the terrain is vulnerable, necessitating a longer closure than simply an immediate clean-up.
“The mountain is still moving a little bit. They can't open the road until we're positive that nothing will happen.”
Motorists could risk the detour entirely by simply change routes, adding about 50 miles to the trip.
Driving south past Cincinnati take I-71 south to Louisville, then I-65 to Nashville, and finally I-24 to Chattanooga, where you rejoin I-75.
Northbound drivers can reverse the route, departing I-75 at Chattanooga.