This discussion of problems from the standpoint of a contractor, emphasizes the full consideration of overall costs. The standardization of tunnel sizes must receive its impetus from owners and designers. The major cost savings will be in the tunnel excavation equipment. Standardization of tunnel sizes must start from excavated diameter of the tunnel, or the excavated size of a horseshoe opening. Enough flexibility should be designed into this excavation size to allow for various types of temporary support such as a rock-bolt-system, a steel-rib system, or a precast-concrete- block system. The flexibility should extend to reasonable tolerances in line and grade. The standardization of machinery is the optimum goal. Utilization of equipment would then be much higher than at present. Standardization of primary excavation equipment can be followed by locomotives, muck cars, agitators, concrete forms and jumbos. Standardization could lead to a ready market for used concrete forms. The main savings to the mining industry will be in better equipment, which gives the manufacturer the incentive to build better in a limited classification. This will lead to repetition of sizes and lower prices. Estimates show that 7 percent of the total cost is spent on custom-built equipment. Further advantages in standardization include reduction in engineering and decision-making time, and faster and more accurate budget estimates. It is indicated that the mining and tunneling industries need not follow different routes in similar operations. Generally the factors of safety built into ground openings amply compensated for loss of strength in using larger size of opening by permitting selection from a standard set of sizes. Observations are also made regarding A-, B-, and C-lines, temporary support, and minimum radus curves for tunnel diameter.

  • Supplemental Notes:
    • Report of a symposium conducted by Standing Subcommittee No. 5, International Activities of the U.S. National Committee on Tunneling Technology, held on May 21-22, 1974 in Washington, D.C.
  • Corporate Authors:

    National Research Council

    National Committee on Tunneling Technology
    Washington, DC  United States  20418
  • Authors:
    • Cronin, H E
  • Publication Date: 1975

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Filing Info

  • Accession Number: 00127938
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 21 1976 12:00AM