In January 1974, a production efficiency study was conducted on one truck-mounted rotary drill and two wagon-type percussion drills. The study was conducted in a rock quarry in Northern Virginia. The quarry material encountered was a grayish black granite with many vertical shale seams. Standing water was encountered on the floor of the quarry in some areas. Drills working in these areas encountered numerous delays directly related to the water, such as, hung bit, excessive cleanout of the hole, and reworking of the hole. The rotary drill, Drill A, used a 6-1/2-inch button bit. The two wagon drills, Drills B and C, used 3-1/2-inch percussion button bits. Checks made on the percussion bits showed them to have a bit life of approximately 950 feet per bit change for this material. Major delay time totaled 49 percent of the Total Work Time Studied (TWTS) for the rotary drill and averaged 25 percent for the wagon drills. The primary type of major delay encountered by Drill A was maintenance/repair of the drill assembly. Start late-quit early and blasting dealys were the most significant delays incurred by the percussion drills. Minor delays for the wagon drills totaled 10 percent of the MWTS, a percentage greater than all productive elements except drilling. Minor delays for the rotary drill were 9 percent of the NWTS. Repairs to the drill assembly and hung steel were the predominant minor delay types for all three drills. /Author/

  • Corporate Authors:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Kolsky, C L
    • Fowler, C M
  • Publication Date: 1974-4

Media Info

  • Features: Tables;
  • Pagination: 14 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00165544
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-RDDP-PC-617
  • Files: TRIS, USDOT
  • Created Date: Jan 30 1978 12:00AM