LABORATORY TESTING OF SCALE MODEL INTERSECTIONS . PROCEEDINGS OF THE FIRST INTERNATIONAL WORKSHOP ON SCALE EFFECTS IN ROCK MASSES, LOEN, NORWAY, JUNE 7-8 1990

This article describes research in which quasistatic laboratory experiments were performed on unlined, scale-model 20 degrees Y-intersections cast in HF4 grout with properties representative of either medium strength rock in an intact condition or high strength rock in a jointed condition. The specimens were loaded in uniaxial strain up to closures in the intersection cavity of about 10%. Our objectives were to compare the response of unlined intersections with that of single straight tunnels and to quantify the effect of pillar strength on intersection response. We found that the basic response mechanism for unlined Y-intersections is the same as for straight tunnels: material at the springlines breaks up, allowing the crown and invert to come together as undamaged blocks. The measured vertical tunnel closure in the intersection cavity is linearly related to vertical closure in unlined straight tunnels. The ratio of intersection closure to straight tunnel closure at a given load, called the intersection shape factor (ISF), provides a useful tool for characterizing intersection response. The area around the pillar is the weakest location, having an ISF of about 2.0. The corresponding strength of the intersection, defined as the load to cause 5% vertical closure, is 80% of the strength of a straight tunnel. Reinforcing the pillar significantly decreases the ISF to 1.2. Removing part of the pillar does not significantly affect the response of the intersection. (Author/TRRL)

  • Availability:
  • Corporate Authors:

    AA Balkema

    P.O. Box 1675
    Rotterdam,   Netherlands  BR-3000
  • Authors:
    • Simons, J W
    • COLTON, J D
    • Florence, A L
  • Publication Date: 1990

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00609544
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • ISBN: 90-6191-660-7
  • Files: ITRD, TRIS
  • Created Date: Jun 30 1991 12:00AM