As part of the trend towards faster underground hard rock development, particularly for large block cave development, Caterpillar has launched a new hard rock cutting machine at MINExpo 2012, with trials of a finished prototype expected to commence “within months.” The company states: “Coal mining has long moved on to high- performance continuous processes – replacing the use of explosives with shearers, plows and continuous miners. Imagine if a continuous miner approach could be used for hard-rock mine development. The patented, activated cutting head promises “to revolutionise hard-rock mine development and selective mining of ore.” One concept complete machine, the RH35 (RH standing for Rock Header) has been designed though has not yet been built, with the 35 standing for the 3m by 5m heading dimensions.
“We have been working on technology for continuous cutting of hard rock for some time, and we plan to begin trialing the technology in mines soon,” says Dr Ulrich Paschedag, General Manager, Underground Products, Caterpillar Global Mining. Technical details of the cutting technology are not being released yet due to ongoing development work, but Paschedag describes the technology as “similar to the success of percussive drilling as compared to conventional drilling.” Caterpillar engineers envision the new cutting technology will be used in a number of different types of hard rock mining systems: “For example, a compact and versatile unit could cut and load hard rock in a continuous, automated process. Such a system would enable high-speed mine development and faster access to ore deposits. Guidance systems and automated cutting processes would ensure maximum cutting-path accuracy, and selective extraction of ore and waste would improve mine yield and cut disposal costs.”
This new launch follows on from progress with the new Rock Flow System (RF300 Rock Feeder and RM900 Rock Mover) continuous haulage system that is being installed as a full project at Codelco Andina following previous testing at Codelco El Salvador and for which details were first published in IM. Cat describes its strategy in this area of underground mining as “providing the most innovative UG Hard Rock products and systems which help customer to increase safety and performance” and leading “in the paradigm shift to continuous hard rock mining by launching innovative continuous extraction and haulage machines for different applications” as well as replacing drill and blast with innovative cutting technologies in combination with a high grade of automation to provide an increased level of safety.
Prior to the current Caterpillar hard rock cutting announcement, before the acquisition by Caterpillar, Bucyrus had tested its activated cutting technology (ACT) at KGHM Polkowice in Poland. ACT adopted the so-called undercutting method, which made use of the fact that the tension and shear strength of rock is generally less in terms of magnitude than the compressive strength. Bucyrus at the time described the process as “chipping towards a free face” and highlighted the fact that cutting forces and, in turn, tool wear, are significantly lower in undercutting compared to conventional frontal attack, making the method more suitable for hard-rock cutting.