Engineering & Mining Journal

DEC 2012

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GROUND CONTROL One of the big benefits of the new generation of TSLs is their use in confined places where shotcrete application would be difficult. (Photo courtesy of Spray On Plastics) in the next two years. These systems are focused on improving the cure times and the application process, he said. While Minova's focus has been on cement-based TSLs, Canadian company Spray On Plastics has developed a twopart polyurea product, RockWeb. Technical specialist Tyler Macpherson's view is that the biggest advance in TSL technology has been the ability to use liquid RHSF (reactive, high-strength, flexible) TSLs to cover irregular or broken surfaces. These systems provide the absolute highest tensile strengths available, he stated, can cure without the need for, or interference from moisture, and develop their strength much faster than other types of systems—in hours compared with days. "Most significant is the webbing technology that allows us to do this," he added. "We have also done considerable equipment development that has made application quick and easy, and we have created bonding systems for excellent adhesion to rock and concrete. We have also developed state-of-the-art equipment that makes mobilization fast and simple: no different from hooking up a drill jumbo or bolter," Macpherson said. DSI North America claims leadership in inflatable expansion bolt and coating 50 E&MJ; • DECEMBER 2012 technologies, and is working on expanding further the ground conditions for which inflatable expansion bolts can be used. The company told E&MJ; it has also developed a major role in the supply of hard rock cable-bolt and resin technologies, while its engineering staff has extensive experience in helping its customers with geologic analysis and product development. BASF's Hage noted that the company has made significant contributions in advancing ground-support technology, with a comprehensive range of chemicals and equipment for wet-mix sprayed concrete in particular. Its R&D; team is continuing to develop solutions through expertise in cement chemistry, concrete technology and material science, he added. The Challenges and Solutions In practice, of course, ground-support systems are only as good as the standard of installation or application. A poorly designed support system will not perform well in the long term, and may not even address immediate safety issues such as spalling where the surrounding rock mass has been damaged during excavation, or where inherent geotechni- cal features bring the potential for localized failures. Such concerns have led to the increased use of shotcrete and mesh, with roofbolts providing the compressive arch needed for durable selfsupport. E&MJ; asked each of the respondents what challenges they see in installing modern roof-support systems, and how these can be overcome. DSI: All underground mining operations see ground control as a major expense, so partnering with DSI allows the operator to have a business partner with industry-leading expertise, innovative products, and superior service and support with experienced professionals. These elements are strategic to allow underground mining and tunnelling operations to be safe and productive. Harker: "In relation to TSLs, challenges include the ease of application and adaption to the current equipment available in mines and controlling the quality of the application. A design thickness of 5 mm is very hard to achieve consistently on a rough rock surface with no gaps in the spray." Macpherson: "We see a lot of work rehabbing broken shotcrete. Damaged shotcrete is very difficult to fix by overcoating because the cracks propagate through the new shotcrete. Also, in places like electrical substations or refuges, the equipment inside cannot be removed for shotcreting so it difficult to repair because of rebound cleanup and 'collateral damage' to infrastructure. In some cases, a shotcrete nozzleman cannot even get access because of the bulk of his hoses." Hage looked at a different perspective: "The major challenges to the industry are establishing enough qualified professionals to meet industry demand, and the involvement of individual people and companies in the industry who don't understand the business of ground support. This leads to inferior solutions being offered, and inadequate training of their representatives and industry personnel. The solution would be to introduce industry-accepted training packages and ensure the certification of nozzlemen." Depth-related Challenges Increase With mines getting deeper, rock conditions will inevitably become more challenging. E&MJ; sought the respondents' views on the key areas of ground-control www.e-mj.com

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