The state of the art in machine tunneling is described as well as future research efforts needed to improve tunneling operations. Several types of tunneling machines are in use today. The "mole" which uses a rotating cutter head to bore a circular tunnel, is the most commonly used tunneling machine. The road-header machine consists of a rotating milling head studded with hard-faced teeth or picks. Ram arm backhoes have been used successfully on several tunneling projects. This type of excavator can only be used in ground that can be ripped. Tunnel boring machines perform well as long as they are penetrating uniform material free from geological abnormalities or excessive inflows of water. Most machines also occupy the entire tunnel cross section and effectively block access to the face when new excavating methods must be adopted. Further research in machine tunneling should be directed towards rearrangement of the machinery for easier access to the working face; sensing of ground conditions by electronic or alternative means other than costly and slow exploratory drilling; improvements in machine versatility to cope with practically any ground condition; development of a tunnel boring machine that uses slurry with a confined space surrounding the cutter head; construction of a soft ground tunnel in which precast concrete segments are used as a final linear; and lastly, it is recommended that design engineers consider accepting flexibility in tunnel size rather than standardization.

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    • This article appeared in TRB Special Report No. 171, Tunnel Construction: State of the Art and Research Needs. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
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    Transportation Research Board

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Authors:
    • Jacobs, J D
  • Publication Date: 1977

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  • Media Type: Print
  • Features: Photos;
  • Pagination: pp 8-9
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  • Accession Number: 00156032
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: Oct 13 1977 12:00AM