CONTINUOUS UNDERGROUND WALL CONSTRUCTION

UNLIKE THE ORTHODOX SYSTEMS FOR THE CONSTRUCTION OF SLURRY WALLS A SYSTEM USING THE BW LONG WALL DRILL HAS BEEN DEVELOPED AND EXTENSIVELY USED IN JAPAN. THE BW LONG WALL DRILL IS A NEW TYPE OF TRENCHING MACHINE DEVELOPED BY THE TONE BORING CO OF JAPAN FOR TRENCH EXCAVATION AND THE CONSTRUCTION OF UNDERGROUND REINFORCED CONCRETE WALLS IN ONE CONTINUOUS OPERATION. THE MACHINE IS BASICALLY A TRAIN OF FIVE OF SEVEN DRILL BITS OPERATED BY TWO SUBMERSIBLE MOTORS WHICH PERMIT ROTARY BORING WITH LITTLE NOISE OR VIBRATION WHILE CONTINUOUSLY EJECTING THE SLIME PRODUCED BY THE DRILLS. FEED AND DEFLECTION INDICATORS AND ADJUSTABLE GUIDE ASSEMBLY ENABLE THE OPERATOR TO REGULATE BIT PRESSURE AND CORRECT ANY AXIS DEVIATION DURING OPERATION. ROTATION OF THE BITS IS SO ARRANGED TO BALANCE THE TORQUE REACTION FROM EACH MOTOR SO THE DRILL UNIT IS NOT SUBJECTED TO ANY TURNING MOMENT. THE DRILL IS SUSPENDED BY A WIRE ROPE FROM THE DERRICK. A SYSTEM OF FORCED NORMAL AND REVERSE CIRCULATION OF BETONITE SOLUTION IS USED ON THE BW DRILL. THE BETONITE IS PUMPED TO THE DRILLS AND SPRAYED FROM THE TOP OF THE DRILL BITS WITH THE EXCEPTION OF THE CENTRAL ONE TO THE GROUND TO BE EXCAVATED, WHILE FROM THE CENTER BIT CUTTINGS ARE CONTINUOUSLY EJECTED BY AIR LIFT AND DELIVERED TO A MUD SCREEN FOR SEPARATION. WHEN THE DRILL REACHES THE REQUIRED DEPTH, NORMAL CIRCULATION IS STOPPED AND ONLY REVERSE CIRCULATION APPLIED UNTIL THE BOTTOM OF THE TRENCH IS CLEARED OF CUTTINGS. /CEPWR/

  • Supplemental Notes:
    • Vol 66, No 782, P 985
  • Publication Date: 1971-9

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Filing Info

  • Accession Number: 00236256
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 17 1972 12:00AM