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RESEARCH REPORT EOLOGY CONSOLIDATION AND VENTILATION CONTROL DEVICES IN UNDERGROUND MINES: DETERMINATION OF DESIGN, MONITORING AND SAFETY STANDARDS As the mining industry strives to develop a national standard for conformance of ventilation control and geology consolidation devices, the development of new methods of determining specifications not only aids the design of innovative ventilation management strategies, but also provides the industry with the assurance of knowing that their ventilation control devices increase the safety factor in underground mine environments. Technical Executive for PB Energy, Mining and Industry, Michael Salu, reports. While hazards resulting from spontaneous heating, gas migration, explosions and flooding remain a major threat to the safety and productivity of underground mines, specific research into overpressure ratings and integrity testing of ventilation control devices (VCDs), bulkheads and dams remains relatively limited. Given the difficulty to conduct field tests in operational environments, as well as the high variability of mine ventilation and geology conditions, the performance of ventilation control devices poses a significant challenge for underground mines. In Australian studies, a computational engineering model has been developed to determine overpressure-rating standards for ventilation control and geology consolidation devices. With data obtained from live blast testing in an underground mine in Australia, explosion dynamics and structural responses of full size VCDs were analysed and used to calibrate a 3-dimensional finite-element computer model of a VCD subjected to blast loading. This calibration began by transferring actual pressure distribution contours from the testing and then compared axial, bending and shear stresses as well as total loading and deflection between various configurations. The results were then used to develop a design tool that can assess installation requirements for a combination of height, width, over pressure, head of water and a factor of safety for individual sites. With the resultant computational model now widely utilised in underground mines, testing parameters have been extended to determine engineering requirements for water-retaining bulkheads and dam walls, where non-uniform pressure and long-term water resistance are critical to mine safety. As the mining industry strives to develop a national standard for conformance of ventilation control and geology consolidation devices, the development of new methods of determining specifications not only aids the design of innovative ventilation management strategies, but also provides the industry with the assurance of knowing that their ventilation control devices increase the safety factor in underground mine environments. While many underground mining fatalities in Australian mines have been directly attributable to ventilation control failure, the variability of underground mine ventilation and geology conditions continues to challenge the implementation of widespread industry performance standards. Affected by three significant disasters since 1975, the Moura district in central Queensland has presented a substantive case for ventilation and geology control standards in underground mining. The first of these disasters occurred at Kianga Mine on 20 September 1975, where 13 miners died from an explosion found to have been initiated by spontaneous combustion. The second occurred on 16 July 1986 at Moura No 4 Mine when 12 miners died from an explosion thought to have been initiated by one of two possible sources; frictional ignition or a safety lamp. The third of the disasters occurred on 7 August 1994 at Moura No 2 Mine. On this occasion 11 miners died following an explosion. As a result of these disasters, and more specifically the loss of 36 lives, a series of task groups was formed by the Mines Inspectorate to report on various aspects of mine operations and the disasters themselves. In 1998, Task Group no. 5 reported on the development of appropriate standards for construction of underground mine seals and stoppings. New mining regulations that specified the strength requirements for VCDs became effective in Queensland coal mines in March 2001. The Queensland Department of Mines and Energy Safety and Health Division subsequently established a recognised standard for the evaluation of performance of VCDs. This standard provides for either physical testing of VCDs or certification of a design including material strength and appropriate safety factors by a certified professional engineer. Engineered computational VCD modelling With a large number of variables involved in determining the actual strength of a VCD and limited guidelines provided on appropriate material strength or safety factors, in 1998, Australian company, Aquacrete, in co- operation with independent engineering consultants, PB, decided that full-scale explosion testing was needed to determine if VCDs designed to a theoretical model would withstand an overpressure event. While similar testing had been conducted at purpose-built facilities such as Londonderry testing facility in New South Wales, the use of an underground mine in Australia provided full underground confinement of the explosive testing and enabled a wider range of tests to be completed. Testing was carried out on a range of VCD thicknesses, ranging from 100mm to 500mm. Typical VCD size was 4.2m x 4.2m, determined by the dimensions of the mine roadways where the testing was AUSTRALASIAN MINE SAFETY JOURNAL 75