MECHANICAL BORING OF A MIXED FACE TUNNEL

A MACHINE WHICH HAS BEEN USED TO BORE THROUGH LOOSE SOILS, CLAYS AND SILTSTONES IN EXTREMELY VARIABLE CONDITIONS IS DESCRIBED. THIS MACHINE IS EQUIPPED WITH A SLOTTED ROOT SHIELD WHICH PERMITS FOREPOOLING OVER THE TOP OF THE CUTTERHEAD TO STABILIZE CAVING GROUND ABOVE AND AHEAD OF THE BORING MACHINE. THE SUPPORTS ARE DRIVEN FROM THE INSIDE OF THE LAST RING BEAM ANGLING THROUGH THE SHIELD SLOT AND OVER A SLIDING ARCH ON THE BACK OF THE MACHINE INTO THE UNDISTURBED GROUND. THE SLIDING ARCH CONTINUES TO SUPPORT THE FORE POLES UNTIL THE END OF THE ADVANCE CYCLE WHERE ANOTHER RING BEAM IS INSTALLED TO PICK UP THE LOAD. THE EXTENDED ROOF SHIELD ALSO GIVES PROTECTION FOR OTHER ROOF SUPPORT ACTIVITIES. DETAILS ARE GIVEN OF THE DEVELOPMENT OF A 20 FOOT DIAMETER MACHINE CLASSIFIED AS A "MIXED FACE" MOLE. THE DESIGN REQUIREMENTS OF THE TUNNEL ARE REVIEWED. THE SHIELD WAS EQUIPPED WITH 20 PUSH CYLINDERS DEVELOPING 4 MILLION POUNDS THRUST. THE MACHINE IS CAPABLE OF DEVELOPING A CUTTERHEAD THRUST OF ONE MILLION POUNDS. THE CUTTERHEAD DIAMETER MAY BE CHANGED SO AS TO OVERCUT OR UNDERCUT THE SHIELD. THE SHIELD HAS THE ABILITY TO USE ROTARY DISC CUTTERS IN ROCK AND CERTAIN SOILS, AS WELL AS DRAG TEETH IN OTHER SOFT MATERIALS. THE CUTTERHEAD HAS REVERSIBLE DIRECTION OF ROTATION AND VARIABLE ROTARY SPEED. THE CHANGING OF CUTTERS IS A FAIRLY SIMPLE MATTER. THE SHIELD HAS PROVISION FOR CONTINOUS ERECTION OF RIBS AND LAGGING. THE DEVELOPMENT OF THIS MACHINE IS SEEN AS AN EVOLUTIONARY STEP AND FUTURE RESEARCH WILL BE DIRECTED TOWARDS DEVELOPMENT OF A MACHINE WHICH CAN ADVANCE INDEPENDENTLY OF THE TUNNEL SUPPORTS IN ROCK FORMATION.

Media Info

  • Features: Figures;
  • Pagination: p. 1125-36
  • Serial:
    • Volume: 2

Subject/Index Terms

Filing Info

  • Accession Number: 00236581
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 27 1974 12:00AM