hollow-rod drilling

hollow-rod drilling

[′häl·ō ‚räd ′dril·iŋ]
(engineering)
A modification of wash boring in which a check valve is introduced at the bit so that the churning action may be also used to pump the cuttings up the drill rods.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.