TUNNELLING SHIELD BEATS SOFT GROUND CONDITIONS

A SUCCESSFUL DEMONSTRATION OF THE BENTONITE SHIELD WAS RECENTLY GIVEN IN LONDON. THE CYLINDRICAL SHIELD WHICH HOUSES A ROTOR IN A FRONT CHAMBER IS CAPABLE OF WITHSTANDING A PRESSURE OF 2.1 KG/SQ.CM. OF BENTONITE SLURRY PRESSURE AT THE FACE. THE CLOSING DIAPHRAGM CAN ALSO BE DESIGNED FOR HIGHER SLURRY PRESSURES. ROTATION OF THE CUTTER REMOVES THE SPOIL FROM THE FACE AND DISCHARGES IT THROUGH A HOPPER IN A SPECIALLY DESIGNED DOUBLE-TRAP-DOOR DEVICE. THIS CONTROLS THE RATE OF SPOIL EXTRACTION FROM THE PLENUM WHILE ALLOWING THE SLURRY PRESSURE IN THE EXCAVATING CHAMBER TO BE MAINTAINED. THE ROTOR OPERATES IN GROUND WHICH CONSISTS OF STONES ABOUT 200 MM DOWN TO SAND OF 75 MICRONS OR LESS. THE SEPARATION PLANT (A VIBRATING SCREEN AND 4 CYCLONES) CAN BE LOCATED ON THE SURFACE OR IN THE TUNNEL. EXPERIENCE SHOWS THAT A 5 PERCENT FULBENT 570/WATER SUSPENSION GIVES A SATISFACTORY STABILIZING ACTION. ESTIMATED COST OF A SYSTEM SIMILAR TO THAT PRESENTLY IN USE IS GIVEN. /TRRL/

  • Corporate Authors:

    Ground Engineering

    7 Ongar Road
    Brentwood CM15 9AU,   England 
  • Publication Date: 1972-11

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00215769
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: TRIS
  • Created Date: Nov 14 1973 12:00AM