HAULING SHOT ROCK TO FORMER SLIP AREA, WHILE DUMPING A ROCK GOT CAUGHT IN TAILGATE OF TRUCK MAKING LOAD UNBALANCED AND THE TRUCK TURNED OVER ON IT'S SIDE. NO ONE WAS INJURED AND DRIVER OF TRUCK RETURNED TO WORK. NO WORK TIME MISSED. DRIVER TO WATCH AREA OF DUMPING AND LOADER NOT TO OVER LOAD AND TO WATCH LOADS.