BENTONITE TUNNELLING SHIELD BREAKS NEW GROUND

DETAILS ARE GIVEN OF THE BENTONITE SHIELD, A NEW MACHINE WHICH IS CLAIMED TO REDUCE THE COSTS OF TUNNELLING THROUGH NON-COHESIVE GROUND. IT IS SIMILAR TO OTHER EXCAVATOR SHIELDS DESIGNED FOR SOFT GROUND TUNNELLING, EXCEPT THAT THE CUTTING HEAD REVOLVES IN A SEALED CHAMBER FILLED WITH A THIXOTROPIC SLURRY OF BENTONITE CLAY PUMPED IN UNDER PRESSURE. ROTATION OF THE CUTTER HEAD REMOVES THE SPOIL FROM THE FACE AND DISCHARGES IT THROUGH A HOPPER INTO A SPECIALLY DESIGNED EXTRACTION DEVICE. THIS CONTROLS THE RATE OF SPOIL REMOVAL WHILE ALLOWING THE SLURRY PRESSURE TO BE MAINTAINED IN THE EXCAVATING CHAMBER. THE BENTONITE PENETRATES THE GROUND AHEAD OF THE MACHINE, FORMING A SKIN THAT SEALS THE TUNNEL FACE, A PRESSURE RESISTANT MEMBRANE, AND ALSO A WATER-TIGHT ANNULUS AROUND THE TUNNEL. THE MIXTURE OF SLURRY AND SPOIL IS PUMPED TO A SEPARATING PLANT ON THE SURFACE. THE MACHINE IS BEING TESTED IN THE EXCAVATION OF LONDON TRANSPORTS FLEET LINE. /TRRL/

  • Authors:
    • Patey, D R
  • Publication Date: 1972-9

Media Info

  • Features: Figures; Photos;
  • Pagination: p. 34-5
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00237018
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: TRIS
  • Created Date: Nov 14 1973 12:00AM