EE WAS SERVICING AN UNDERGROUND HAUL TRUCK AT THE SURFACE SHOP AREA. AFTER FUELING THE TRUCK, THE EE MOVED THE TRUCK TO ADD OIL. EE STATED THAT HE BEGAN TO FEEL NAUSEOUS SO HE STOPPED THE TRUCK. HE STATED THAT HE INTENDED TO DISMOUNT THE TRUCK BUT DOES NOT REMEMBER DOING SO. THE EE WAS FOUND LYING NEXT TO THE TRUCK WITH A HEAD WOUND. THE TRUCK WAS SHUT OFF AND THE PARK BRAKE