The identification of the nature of the ground support problem encountered or anticipated is the first step in the selection and design of shotcrete for temporary support of ground excavation. The compatibility of shotcrete with the particular problem must then be evaluated. Consideration must be given to whether or not the use of an alternative support system may be more practical than the use of shotcrete. Previous underground experience will provide sufficient guidelines for selection and design of shotcrete thickness and coverage for use in supporting loosening loads or use as a surface seal. The shotcrete thickness needed for support of overstressing or swell loads can be determined following ultimate strength concepts of concrete behavior. The relevant factors in the selection of shotcrete for temporary support are compatibility with ground behavior and practical considerations. Common problems encountered are: difficulty in developing good quality shotcrete around and behind wood blocking installed in the steel ribs; difficulty with overbreak requiring excessive volumes of shotcrete to fill the space between the ribs and excavated surface; and difficulty in developing adequate shotcrete "blocking" between the steel ribs and the excavated rock. Different criteria are used in the selection or design of the thickness and coverage of shotcrete for temporary support of underground excavations, depending upon the function which the shotcrete is intended to fulfill. Details are outlined of the use of shotcrete for problems associated with surface seal. Support of loosening loads, and support of overstressed and seedling ground. A table is presented of the typical shotcrete application in the temporary support of 15 to 20 ft. diameter tunnels experiencing loosing loads.

Media Info

  • Features: References; Tables;
  • Pagination: p. 160-174

Subject/Index Terms

Filing Info

  • Accession Number: 00263688
  • Record Type: Publication
  • Report/Paper Numbers: SP-45 Conf. Proc
  • Contract Numbers: H0111881
  • Files: TRIS
  • Created Date: Dec 19 1974 12:00AM