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Title: Drill bits for frozen fine-grained soils
Authors: Sellmann, P. V. (Paul V.)
Mellor, Malcolm
Keywords: Cold regions
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Special report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 86-27.
Description: Special Report
Abstract: Successful drill bits for use in frozen sediments have certain characteristics that are not commonly found in commercial bits used for unfrozen soils and rocks. In frozen sediments, drilling characteristics and optimum bit design vary, depending on grain size, ice content, and temperature of the material. Drills for frozen fine-grained material (silt and clay) have specific requirements that differ from those for other frozen soil types. Even with restriction to fine-grained materials, drilling characteristics vary with temperature and ice volume. Soils that are only a few degrees below freezing can cause more problems than similar materials at somewhat lower temperatures because of different fracture and transport characteristics. Our approach has been to work toward optimum efficiency, with special emphasis on reducing thrust and torque requirements for light-weight drills. Important features of drills that perform well in frozen fine-grained materials include: (1) full face cutting, (2) a pilot bit that can cut and clear its cuttings, (3) appropriate cutter angles (adequate clearance angles and positive rake), (4) sharp but durable cutters, (5) unobstructed flow paths for chip clearing, and (6) stabilizing features for smooth running. Examples of successful bits are discussed and illustrated. Some were built or modified at CRREL, while others are of commercial manufacture.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Special Report

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