EE WAS ASSISTING WITH THE LOADING OF BLAST HOLES. WHILE HE WAS SHOVELING IN ONE OF THE HOLES, TWO OF HIS FELLOW WORKERS DECIDED TO ENGAGE IN HORSEPLAY. ONE SHOVED HE BACKWARDS AS THE OTHER TRI PPED HIM UP CAUSING HIM TO FALL TO THE GROUND. THE ADJUSTABLE RATCHET KNOB ON HIS HARDHART SUSPENSION STRUCK THE BACK OF HIS HEAD AS IT MADE CONTACT WITH THE GROUND. THIS IMPACT CAUSE TO TO L