THERMAL SPALLING EXPERIMENTAL DRILLS USE HEAT, ELECTRICITY, MICROWAVES, CHEMICALS

DIFFERENTIAL THERMAL EXPANSION OF CONSTITUENT CRYSTALS AND GRAINS OF ROCKS IS PRODUCED BY SEVERAL DIFFERENT MECHANISMS: HIGH THERMAL GRADIENTS, PHASE CHANGES IN THE MINERALS, DIFFERENCES IN THERMAL EXPANSION COEFFICIENTS OF CONSTITUENT MINERALS, REMOVAL OF WATER OF CRYSTALLIZATION, HEATING OF LIQUID AND GASEOUS INCLUSIONS, AND CHEMICAL BREAKDOWN OF THE MINERALS. THE VOLUMETRIC EXPANSION WHICH QUARTZ UNDERGOES DURING ITS ALPHA-TO-BETA TRANSITION IS ONE OF THE MOST IMPORTANT MECHANISMS IN SPALLING. HIGH THERMAL GRADIENTS ARE ALSO IMPORTANT IN THERMAL SPALLING. MANY ROCKS WILL NOT SPALL BECAUSE THE INDUCED THERMAL STRESSES ARE TOO LOW. IN MANY OF THESE ROCKS, HEATING WILL PRODUCE THERMAL STRESSES SUFFICIENTLY HIGH TO WEAKEN OR BREAK THE BONDS BETWEEN CRYSTALS AND GRAINS. THIS PROCESS IS CALLED THERMAL DEGRADATION, WHICH CAN REDUCE ROCK STRENGTH BY AS MUCH AS 50% TO 75%. DIAGRAMS AND DISCUSSIONS ARE PRESENTED OF THE FOLLOWING TYPES OF THERMAL SPALLING EXPERIMENTAL DRILLS: JET PIERCING DRILLS, FORCED FLAME DRILLS, ELECTRIC DISINTEGRATION DRILL, HIGH-FREQUENCY ELECTRIC DRILLS, MICROWAVE DRILLS, INDUCTION DRILLS, AND CHEMICAL DRILLS.

  • Supplemental Notes:
    • Vol 169, No 6, PP 101-106, 4 FIG, 5 TAB, 37 REF
  • Authors:
    • Maurer, W C
  • Publication Date: 0

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  • Accession Number: 00229663
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 15 2004 2:39AM