CONSTRUCTION-PHASE DESIGN CHANGES IN RESPONSE TO A COMPOUND ROCKSLIDE, PREACHER CANYON SECTION OF STATE ROUTE 260, NEAR PAYSON, ARIZONA

The Preacher Canyon Section of State Route 260 is an Arizona Department of Transportation-owned highway located approximately ten miles east of Payson, Arizona in a bedrock terrain. The two-lane highway was reconstructed to a four-lane divided highway on undisturbed forest land, requiring 1.8 million cubic yards of rock excavation. A compound rockslide in granite occurred during construction of a 170-ft deep roadway cut for the project. The compound slide consisted of an initial steep wedge-type failure which then prompted planar movement toward the wedge failure along an adjacent fault, ultimately resulting in a unique low-angle wedge failure in the weakened rock mass. The slide included head crack development, slow creep-type movement extending to within 25 ft of the toe, and internal cracking. Initially, remedial design of the original 3/4H:1V slope necessitated flattening the slope to 1-1/4H:1V, de-energizing a critical 345-kV transmission line serving the Phoenix area, removing and relocating an existing steel transmission line tower, temporarily supporting the line on wood poles, and stabilizing the ground at the base of the poles with rock anchors, as the failure projected to above the temporary poles. The design also required construction of a rockfall containment system to prevent rocks rolling from the flattened slope onto the roadway. To retain the visual characteristics of the surrounding area, a deepened cut ditch was installed in lieu of a rockfall barrier. Continued creep movement of the slide necessitated a final adjustment to the design to remove more head mass and additional slope recontouring to mitigate further movement and reduce required future maintenance.

  • Supplemental Notes:
    • Unlike most groups and organizations that meet on a regular basis, the Highway Geology Symposium has no central headquarters, no annual fees, and no formal membership requirements. The governing body of the Symposium is a Steering Committee. Recent proceedings may be obtained from the Treasurer of the Symposium, Mr. Russell Glass.
  • Corporate Authors:

    Mr. Russell Glass

    100 Wolf Cove Road
    Asheville, NC  United States  28804
  • Authors:
    • LaMont, D
    • Melita, J
    • Peterson, D E
    • LaFronz, N J
  • Conference:
  • Publication Date: 2002

Language

  • English

Media Info

  • Features: Figures;
  • Pagination: p. 99-111

Subject/Index Terms

Filing Info

  • Accession Number: 00962016
  • Record Type: Publication
  • Report/Paper Numbers: CD-ROM
  • Files: TRIS
  • Created Date: Aug 8 2003 12:00AM