The stabilizing and upgrading of an older highway benched into an unstable slidding hillside is described. The solution involved drilling 24 in. diameter holes, 100 ft. deep in hard rock and using drilled in pilings tied back into the hill with post-tersioned rods and cables. 600 drilled-in pilings were installed along the outer edge of the highway bench. Large 14-in. steel H-beam reinforcements were positioned in each 24 in. diameter hole and other grouting and filing with concrete to grade, pilings were tied back to the hillside. Using a large downhill drill, the construction team average six to seven completed 24 in. diameter piling holes daily, at a rock penetration rate of 20-ft. per hour. The drilling project was completed in two stages. The first shift, using an auger drill, drillled through the upper layers of weathered, fractured, and broken rock and soil. When they hit the hard rock, the second shift came in. A big hammer drill equipped with a 150 ft-long boom and a rotary drill unit provided the necessary torque for drill rotation at approximately 12-15 rpm. A calyx basket was installed above the drill to catch the cuttings blown up the hole by the drill's exhaust air. The basket required dumping after successive drill penetrations of 3 ft.

  • Corporate Authors:

    Construction Digest, Incorporated

    Box 603, 101 East 14th Street
    Indianapolis, Indiana,   United States  46206
  • Publication Date: 1977-7-21

Media Info

  • Features: Photos;
  • Pagination: p. 23-26
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00167483
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 18 2002 12:00AM