INJURED WORKER ATTEMPTED TO DISCONNECT AND REMOVE 2 30' SECTIONS OF 8"" DIA ALLUMINUM IRRIGATION PIPING, TO ALLOW A DOZER TO PASS THROUGH AREA. ON THE SECOND SECTION OF PIPE, ONE OF THE JOINTS WERE STUCK. THE IW LIFTED THE FREE END, PLACED IT IN A HEADLOCK POSITION WITH HIS RIGHT ARM AND MOVED SIDE TO SIDE WHILE PUSHING AWAY FROM THE STUCK JOINT. SUFFERED A HERNIA.