ROCK DRILLING OPERATIONS
From mid-January thru mid-February 1974, time studies were conducted on three wagon-type percussion drills working in a rock quarry in eastern Tennessee. The field study began with two 1968 model drills working at the drill site. During the second week of the study, one of the drills was removed from the site and replaced by a new 1974 model. The quarry material encountered was predominantly a dark colored granite with occasional wide seams of shale. Ground water was encountered on a majority of the holes. As is usual when water is encountered during a drilling operation; a greater amount of time was spent cleaning out and collaring the hole, as well as the occurrence of numerous delays due to hung bits. All three drills used 3 1/2-inch diameter cross wing bits with carbide inserts. Bits, normally sharpened several times before being discarded, lasted for approximately 1,500 feet of drilling per sharpening. Major delay time totaled 29 percent of the Total Work Time Studied (TWTS) with the primary cause attributed to blasting delays. Minor delays totaled 11 percent of the TWTS and were primarily caused by hung bit, and start late - quit early delays. The latter is attributed mainly to the fact that the drill operators were transported into and out of the quarry on company time. Overall efficiency of the operation was 60 percent. Rain ranging from light showers to a heavy downpour was encountered on 11 of the 23 study days. It interrupted operations on the three drills for a combined total of 82 hours of TWTS. Due to the return to daylight savings time, the first two hours of drilling were conducted in the dark. For the most part, this did not seem to adversely affect operations; however, because of company safety policy, on several occasions the drillers were forced to wait until daylight before they could move their compressors to a new drill location. This delay totaled 5.9 hours or 1.6 percent of the TWTS.
Washington, DC USA 20590
- Kolsky, C L
- King, B
- Publication Date: 1974-5
- Features: Tables;
- Pagination: 17 p.
- TRT Terms: Drill bits; Granite; Groundwater; Quarries; Rainfall; Rock drilling; Shale
- Old TRIS Terms: Percussion drill bits
- Subject Areas: Construction; Highways;
- Accession Number: 00261530
- Record Type: Publication
- Report/Paper Numbers: FHWA-RDDP-PC-618
- Files: TRIS, USDOT
- Created Date: Oct 22 1974 12:00AM