Controlled foam injection: a new and innovative non-explosive rockbreaking technology

http://dx.doi.org/10.17159/2411-9717/2017/v117n3a5 Controlled foam injection: a new and innovative non-explosive rockbreaking technology by R.G.B. Pickering* and C. Young† Controlled foam injection, or CFI, is a highly effective, novel non-explosive rockbreaking technology that with appropriate implementation and application can replace traditional drilling and blasting methods with drilling and non-explosive breaking. The CFI technology is safer, more productive, environmentally friendly, and fully developed; and it can operate with the same flexibility as more traditional small-hole drilling and blasting. To date, CFI has been regarded as an interesting rockbreaking process that could be used only in a few specialized applications. However, in extensive trials it has successfully broken every rock type encountered and in reality it could be used in place of all mining and civil engineering rockbreaking processes that utilize explosives in short and small-diameter blast-holes. The narrow-reef hard-rock mines, typical of the southern African gold, platinum, and chrome sectors are under severe pressure to mechanize and preferably operate on a 24/7 basis, and this could be achieved through the application of CFI. What is still outstanding is a suitable machine to fit a defined application, such as tunnel development or stoping. 97"26/. non-explosive rockbreaking, controlled foam injection, mining cyble, continuous operatios. 3062/+-0423 How do we increase productivity using technology as the driver for change? From studies in mining tunnelling it is obvious that developments in drilling technology, as well as increased drilling rates, have not led to a significant increase in the rate of tunnel development. Drilling rates with mechanized drills have increased fivefold in the last 50 years, while tunnel development rates in mechanized mining operations have reduced to about one-third of those 50 years ago. The biggest obstacle to lower cost and safer mining in narrow-reef orebodies, typical of the gold, platinum, and chrome mines found in southern Africa, is the blasting cycle, with its inherent poor utilization of the mining assets. In conventional mining operations, the total face working time is typically less than eight hours per day and less than seven days a week. In reality only 25% of the totally available time is utilized to generate revenue (Fenn, 2016). What is required is a technology that allows for continuous mining, thereby maximizing the use of the asset. By          
* Rod Pickering & Associates, Port Alfred, Eastern Cape, Cape Town, South Africa. † CFI Technologies, Steamboat Springs, Colorado. © The Southern African Institute of Mining and Metallurgy, 2017. ISSN 2225-6253. This paper was first presented at the New technology and innovation in the Minerals Industry Colloquium’, 9–10 June 2016, Emperors Palace, Johannesburg, South Africa.  
  
 237 L 32).4. implementing some form of non-explosive mining the rate of face advance can be increased and the length of face being worked can be reduced, which leads to more concentrated mining. Concentrated mining means less service infrastructure, less ventilation, and more effective management. In soft-rock mining this has been achieved with the introduction of pick-cutting machines, such as road-headers, shearers, and continuous miners. The introduction of pick-cutting in the coal mining industry in the 1950s led the move away from blasting and by the mid1990s fatalities, measured in deaths per million tons produced, had reduced to only 1.6% of the 1947 figure and productivity at British Coal, measured in tons per employee, had risen by more than 20 times compared to the blasting era (Pickering, 2004). Replacing blasting with cutting also reduces the blast damage to the surrounding rock and increases safety. Operating 24/7 results in much higher rates of face advance in development ends, leading to shorter lead times to production and better NPV returns Thus, we see that the move to non-explosive mining had a major impact on safety, productivity, operating costs,, and return on invested capital. The only rock-cutting machines that have been operated successfully in hard-rock mining are raise-boring machines and, in very limited applications, tunnel-boring machines (TBMs). All these machines use discs or buttons to break the rock, primarily in compression; and to overcome the high Controlled foam injection: a new and innovative non-explosive rockbreaking technology compressive strength of the rock requires very high forces, massive machines to supply these forces, high power, and consequently high capital cost. This is exacerbated by the high running cost of these machines due to the exceedingly high abrasivity of the rock. To make matters worse, these machines are difficult to manoeuvre, which makes following the reef very difficult, if not impossible, and furthermore they only cut circular openings. Original equipment manufacturers (OEMs) have conducted extensive work, often funded by mining companies, to develop rock-cutting machines for hard-rock mining. Because of the inherent inefficiencies of cutting hard rock in compression, some OEMs have developed rockcutting machines that attack the rock in an undercutting mode to break the rock in tension, as the tensile strength of these hard rocks is 5–10% of the compressive strength. Some examples are: To date, no-one has been able to develop a hard-rock cutting machine for everyday commercial use in the mining industry, other than for the specialized application of raiseboring circular shafts and a few specialized TBM-driven mine access projects. The above story is interesting and has been told many times to justify the introduction of new technology. However, the recent work carried out by the Chamber of Mines sheds a new light on the possible future of the gold and platinum mines in South Africa. This work was presented at the New Technology and Innovation in Mining Colloquium organised by the SAIMM and is part of the Mining Phakisa initiative. Figure 1 shows predicted production from the gold and platinum mines in South Africa. In each graph the block on the left is production from conventional mining and indicates the predicted closure of the gold and platinum mines by 2026; unless the mines mechanize. The central block indicates an increased lifespan if the mines are mechanized with drill-and-blast operations, and the block on the far right shows how the life of the mines could be extended until the middle of this century through the introduction of nonexplosive mechanized mining operating 24/7. It has been stated that without this drive to modernize mining it will not be possible to unlock the potential to: ® Achieve zero harm and get closer to the goal of eliminating fatalities ® Mine South Africa’s deep-level orebodies profitably. ® The Mobile Tunnel Miner (MTM6) (...truncated)