Ore flow velocity is less in inclined ore pass

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Unformatted text preview: For the same elevation difference vertical ore pass is shorter, less direct hit or impact to sided walls, easy to drive, slash (if required to enlarge their capacity) and maintain. Vertical pass does not require knuckle and has none of the problems inherent with knuckles. Ore flow velocity is less in inclined ore pass, therefore, there is less problem with entrained air, fragmentation and dust. For some conditions ore and ore pass, arching is less likely in an inclined pass due to imbalance of normal forces. Glory Hole Ore Passes:16 For some mining applications at high altitude, very long vertical ore passes are required. These long passes are normally excavated with a raiseborer. They are similar to the long waste rock passes except that they are normally run empty while a waste rock pass is designed to be kept nearly full. The glory hole ore passes have all the problems of regular ore passes (as described in the preceding paragraphs), plus some of the following problems. Air Blast: Because this type of ore pass is normally designed to feed directly into an underground bin, it is run empty. This means that the ore stream obtains very high velocities resulting in intermittent air blasts due to piston effect that must be relieved by an underground connection to a relief airway. A second ore pass connected to the same bin underground may provide the required relief. Ricochet: The high velocity of the ore stream produces tremendous impact at the bottom of the raise; therefore, the geometry is designed to provide an impact bed (rock © 2005 by Taylor & Francis Group, LLC 354 SURFACE AND UNDERGROUND EXCAVATIONS box) at the bottom of the raise. In some cases, liners are required to take care of the ricochet (bounce) from the rock box. Another ricochet phenomenon occurs when the glory hole raise is fed with a conveyor. The horizontal motion of ore on the conveyor continues when the ore stream falls into the raise. The result is a first impact on the far side of the raise and subsequent ricochet to the near side. If nothing is done to mitigate this action, it produces wear in the upper portion of the raise. Attrition: The loss of potential energy due to the drop of the ore stream is divided between friction and comminution of the ore. The total potential energy is simple to calculate. The portion of this energy that results in attrition is difficult to estimate in advance. The amount of attrition is important if the ore is to be treated in an autogenous mill. If the ore has a high work index, and a conservative fraction is assumed for comminution, the amount of reduction in lump size is not normally significant. In some cases, such as a limestone quarry or a rock fill quarry, the generation of fines by attrition may result in an unsatisfactory product. REFERENCES 1. Agoshkov, M; Borisov, S. and Boyarsky,V Mining of Ores and Non-metallic Minerals. .: Mir Publishers, Moscow, 1988, pp. 67–69. 2. Alimak: Raise Climber (leaflets). Vein Mining, 1977. 3. Atlas Copco – Robbins: Leaflets and website, 2002. 4. Atlas Copco: Raise driving with Jora Hoist, 1970. 5. David, J.S. and Pfleider, E.P.: Ore-pass, Tunnels and shafts. In: Surface Mining, E.P. Pfleider (edt.)AIME, New York, 1964, pp. 637–642. 6. Hamrin, H.: Guide to Underground Mining Methods and Application. Atlas Copco, Sweden, 2002, pp. 12–13. 7. Home, L.W.: Raise Drills. In: Underground Mining Method Handbook, W.A. Hustrulid (edt.). SME (AIMMPE), New York, 1982, pp. 1093–1097. 8. Jimeno, C.L; Jimeno, E.L. and Carcedo, F.J.A.: Blasting and Drilling of Rocks. A.A. Balkema, Netherlands, 1997, pp. 241. 9. Kolihan Copper Mine, India.: Technical Innovations – Long-hole Blasting, 1986. 10. Olofsson, S.: Applied Explosives Technology for Construction and Mining. Applex, Sweden, 1997, pp. 160–170. 11. Paul, R.B. and Eric, G.B.: Drifting and Raising by Rotary Drilling. In: Cummins & Given (eds): SME Mining Engineering Handbook. AIME, New York, 1973, pp. 10: 89–97. 12. Selleck, D.J. and Pfleider, E.P.: Ore passes, Tunnels and Shafts. In: Surface Mining, Vol. II, 1994, pp. 6: 38–40. 13. Singh, J.: Heavy Constructions – Planning, Equipment and Methods. Oxford & Ibh Pub. New Delhi, 1993, pp. 554–560. 14. Svensson, H.: Rasie Climbers. In: Underground Mining Method Handbook, W.A. Hustrulid (edt.). SME (AIMMPE), New York, 1982, pp. 1051–1055. 15. Tatiya, R.R.: Longhole Raising, Mining and Engineering Journal Vol. 18, 1979, pp. 1–8. 16. Vergne, J.N.: Hard Rock Miner’s Handbook. McIntosh Redpath Engineering, 2000, pp. 324–329. © 2005 by Taylor & Francis Group, LLC...
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