Abstract
This is the second in a series of Bureau of Mines reports that describe experiments designed to devise an efficient, economic mechanical fragmentation technique for hard rock. The previous study described the development of the ripper cutting technique to successfully cut hard rock with 3- to 6-in-wide drag cutters. This study was conducted to test the ripper cutting technique at full scale using 9-in-wide drag cutters. The experiments were conducted with a special test device that cut shallow 6- by 6-ft openings in 9,200-lbf/in2 compressive-strength concrete blocks. The tests showed that ripper cutting can excavate large-scale openings of the type required by the mining industry at a production rate that outperforms the conventional drill-blast technique. Moreover, the system can produce openings of various sizes and shapes, is simple to operate and maintain, and produces very little dust or noise during operation. The system appears to meet all of the criteria for a successful hard-rock mining machine.
