A preliminary evaluation of a hydraulic mechanical splitter as a means of breaking rock in a deep-level mine

Abstract

Conventional drill-and-blast practice in deep-level hard rock mining impacts negatively on the immediate environment and alternatives are frequently sought for efficient, continuous, automated and safe rock breaking. The current method for breaking rock, drilling and blasting, is a “cyclic” activity where the rock mass is drilled, blasted, cleaned and the area supported. The mining process must be completed within the blasting times. Continuous rock breaking presents the opportunity to eliminate the “cyclic or batch” mode and improve productivity. Such a system for non-explosives continuous rock breaking is the hydraulic rock splitter. The choice for the splitter is the equipment is relative simple, easy to use, readily available and affordable, and has been successfully used in the construction and civil industries. The purpose of this study was to evaluate the functionality and applicability of the hydraulic mechanical splitter in deep-level hard rock mining. The specific instrument used in the study was the DARDA® hydraulic splitter. Rock breaking with the use of a hydraulic splitter has a place in niche applications in an underground mining operation. The static hand-held tool has distinct advantages in restricted areas. The unit is simple in design and is easily integrated into existing mining operations, and neither does it require a highly technical skilled workforce or expensive maintenance. A literature study was undertaken, with the main focus on non-explosives rock breaking where a hole needs to be drilled into the rock mass. A device or application is inserted into the hole to fracture the rock mass. The specific DARDA® hydraulic splitter used during the trials required a hole diameter of 45mm to 48mm and a minimum hole length of 680mm. Several trials were conducted on surface and underground. The most challenging process in mechanical rock splitting is to create a free face in the stope. In the trials four different “cut” layouts were evaluated to create a second free face. The trials highlighted the importance of quality drilling in terms of collaring the hole, hole length and directional accuracy. The results showed the potential of the DARDA® hydraulic splitter. Drilling the least number of holes produced the least amount of rock. The greater the cross-sectional area of holes drilled, increased the amount of broken rock and resulted in easier splitting, due to the increased void. The mass of rock broken per cut varied between 30 kilograms to 65 kilograms with cross-sectional areas of 0.09m2 and 0.144m2 respectively. The operational learning included the frequent lubrication of the feathers and the wedge. The unit needed to be supported during the splitting process, small rock fragments were caught between the moving parts. Fragments deep inside the “cut” area had to be removed manually and during the splitting process, starting at the hanging wall, obscured the holes close to the footwall due to rock fragments on the footwall. To alleviate a number of operational issues experienced during the trials, include the automation of the lubrication of the feathers and wedge, supporting the cylinder unit during the splitting process and small stones wedged between the moving parts to be removed prior to inserting the splitter into the next pre-drilled hole. The cross-sectional area of the cut should be as large as possible for the rock fragments to easily fall to the foot wall and the splitting process should start from the bottom to the hanging wall to not obscure the drilled holes with rock fragments.