Installing a huggy clamp to couple 2 pieces of SDR9 8"" DRISCO pipe one end of the pipe released, striking the miner on the left cheek, temple and eye. Initial eval; concussion, released for 7 days of modified duty. Returned to work, 2 days later sent back for re-eval, admitted for 2 days, observation only. Released, diagnosed w/ post-concussion NO Work until follow up in 7 days.