COMPARING FOAM WITH HIGH-DENSITY SLURRY

This article describes research by Neyrpic Framatome Mecanique (NFM) on the use of foam instead of high-density slurry in an earth-pressure balanced (EPB) tunnelling shield, and compares the use of foam and high-density slurry in such a shield. The research on alternatives to the use of high-density slurry in the shield arose because that system has several disadvantages. NFM's approach is to replace the incompressible slurry by an expandable product, which can fill voids in the soil regardless of a change in material size during the pressurised excavation process. NFM has developed a type of foam which is made from surface active reagents, water and air, and consists of micro-bubbles of air which clog openings in the excavated face and block the inflow of water. This foam injection technique has rapidly proved its effectiveness and its cost and environmental benefits, and it has replaced the use of high-density slurry on many EPB shields. The foam is injected into broken ground in front of the tunnelling machine to improve: (1) prevention of water inflow at the face; (2) ground excavation; and (3) homogeneity of the excavated material. The foam is evacuated with the spoil and not recycled. NFM's tunnel borer can be adapted to use either foam or high-density slurry, according to the tunnelling requirements.

  • Availability:
  • Corporate Authors:

    THE MINING JOURNAL LTD

    60 WORSHIP STREET
    LONDON,   United Kingdom  EC2A 2HD
  • Authors:
    • THEVENET, M
  • Publication Date: 1996-2

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00725473
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Sep 26 1996 12:00AM