Drill Bits for Frozen Fine-Grained Soils

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 mat...

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Bibliographic Details
Main Authors: Sellmann, Paul V., Mellor, Malcolm
Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
Format: Text
Language:English
Published: 1986
Subjects:
Snow
Ice and Permafrost
*SOILS
*CUTTERS
*DRILLS
REQUIREMENTS
ANGLES
TEMPERATURE
VOLUME
LOW TEMPERATURE
OPTIMIZATION
MATERIALS
EFFICIENCY
COLD REGIONS
GRAIN SIZE
FLOW FIELDS
FREEZING
ICE
TRANSPORT
CLAY
LIGHTWEIGHT
SEDIMENTS
TORQUE
CLEARANCES
FINE GRAINED MATERIALS
SILT
PERMAFROST
RAKE ANGLES
*DRILL BITS
*FROZEN SOILS
PE62730A
WU035
AST42
Ice
permafrost
Online Access:http://www.dtic.mil/docs/citations/ADA178113
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA178113
Description
Summary: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 of 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 had 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 of modified at CRREL, while others are of commercial manufacture. Keywords: Cold regions; Permafrost; Drilling; Drills; Cutters.

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