A Public Power Corporation (PPC) worker suffered broken arms and legs while working at a lignite mine area in Ptolemaida, northern Greece, on Monday.
The man, whose age was not given, was on an eight-month contract at PPC. He had been trying to empty the truck he was driving when the ground gave way.
He was hurt trying to get free of his vehicle.
A 43-year-old PPC employee lost his life in a similar manner a few weeks ago.
Unionists have complained about the lack of safety measures at the quarry.