MIXSHIELD ADVANCES IN SOFT GROUND

This article describes the use of Mixshield tunnelling for drilling through soft, unstable, water-bearing ground. There are now two distinct soft-ground excavation methods: (1) the slurry technique; (2) the earth pressure balance (EPB) principle. There are many options and features designed to cope effectively with different ground conditions. The slurry shield principle is to fill the excavation chamber with a bentonite slurry fluid, that provides ground support and carries away excavated material. In Mixshield systems, the supporting fluid pressure is controlled by a cushion of compressed air on the free fluid surface behind the diaphragm at the back of the work chamber. The first Mixshield was built in 1985 for the 6.5km long HERA nuclear particle ring tunnel laboratory in Hamburg. In a significant pressurised tunnelling machine development, a 7.7m diameter Mixshield was used on the Lille Metro in 1986. An 11.6km diameter Mixshield was used in constructing the Grauholz rail tunnel in Switzerland. Two new innovations were introduced for the 8.3km diameter Mixshield for the Essen Metro. The article also describes an EPB system being developed by Herrenknecht, explains the respective merits of slurry and EPB systems, and examines the future prospects for Mixshield use.

  • Availability:
  • Corporate Authors:

    THE MINING JOURNAL LTD

    60 WORSHIP STREET
    LONDON,   United Kingdom  EC2A 2HD
  • Authors:
    • Wallis, S
  • Publication Date: 1994-3

Language

  • English

Media Info

  • Pagination: p. 63-5,67
  • Serial:
    • WORLD TUNNELLING
    • Volume: 7
    • Issue Number: 2
    • Publisher: THE MINING JOURNAL LTD
    • ISSN: 0956-8700

Subject/Index Terms

Filing Info

  • Accession Number: 00668075
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Nov 2 1994 12:00AM