The article discusses the design of the hydroschild soft ground tunnelling machine and its use in the construction of the Wilhelmsburg sewer tunnel project. The machine is designed for sub-aqueous tunnelling in dense sand at a depth of 15-20 M although in this project the 4.34 M diameter tunnel had a minimum cover of 6 M beneath shipping channels. For this construction compressed air was used with a bentonite/water suspension as a soil sealing and stabilising fluid, which was also used to carry solid material to the surface. This was then separated and the slurry returned to the cutting shield for re-use. A feature of the machine is that the shield is introduced at an angle of 70 degrees to give protection against soil instability at the crown. The pressurised thixotropic fluid in front of the shield ensures continuous grout penetration into the surrounding sand leaving a continuous skin of bentonite gel on the tunnel surface. The finished tunnel lining was provided by pre-cast concrete segments bolted together in circumferential and longitudinal directions. /TRRL/

  • Corporate Authors:

    Foundation Publications Limited

    7 Ongar Road
    Brentwood CM15 9AU, Essex,   England 
  • Authors:
    • Braun, W M
  • Publication Date: 1975

Media Info

  • Features: Figures; Photos;
  • Pagination: p. 40-44
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00134387
  • Record Type: Publication
  • Source Agency: ARRB Group Ltd.
  • Files: ITRD, TRIS
  • Created Date: Dec 15 1976 12:00AM