Proc Conf on Shaft Drilling Technology Las Vegas Inst Shaft Drilling Technol 1991 :10 pages
As part of its continuing research to strengthen the competitive position of the U.S. minerals industry by improving the efficiency of underground hard-rock mining, the U.S. Bureau of Mines is conducting research on continuous mechanical extraction systems to replace the cyclic drill-blast-muck system in common use. One product of this research is a fragmentation method called ripper cutting. This concept uses a single, wide bit that attacks the rock at a shallow angle and slow speed. Research has demonstrated that the system is capable of excavation rates exceeding those possible with conventional drill-blast and can effectively cut rock too hard for roadheaders or drum-type miners. The concept has the additional advantages of low bit wear and low dust generation. The ripper cutting system can be configured as a development machine, a hard- rock mining machine, or a shaft-sinking machine. This paper presents the results of full-scale laboratory tests conducted in both soft and hard rocks using two different cutterheads. It also includes a comparison of ripper cutting to systems currently used from the standpoint of energy efficiencies and operating costs.
Proc. Conf. on Shaft Drilling Technology, Las Vegas; Inst. Shaft Drilling Technol., 1991, 10 Pp
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