| Magnetic deposit in Xiaowanggou iron mine results from sedimentary and metamorphic activities of the earth. The orebody is nearly bedded, the length of it varies from150m-300m, dipping from25°to40°,a maximum length of400m is measured at this direction, the vertical thickness is from20m-90m, it pitches15°-35°at the north-to-south direction. Taking advantages of small value of angle, three areas from top to bottom are separated for mining including upper, middle and lower part. Total production capacity is expected to2.2million t/a. It is noteworthy that there are affluent thick orebody in lower area, where production capacity reachs1.5million t/a. In the light of exceeding mining caused by transition period from open pit to underground, production capacity should be improved as rapidly as possible in order to maintain the high production life. Hence, it urgently need to research the highly intensive excavating techniques for lower part.In this paper, a proposal named "High intensive mining technologies for the lowest mining area using a method which combines sublevel caving with induced caving" is put forward, based on a review of study on high intensive mining technologies and detailed conditions of Xiaowanggou iron mine, in which overlying orebody of intermediate stability will be caved by induced caving and be recovered stage by stage at lower sublevels. The methodology is field survey and indoor test, theoretical analysis and field commercial test. First of all, cavability analysis and fragmentation prediction of ore and surrounding rock is done following rock mass quality classification, whose conclusion is favorable for the mining proposal. Then, optimization of structural parameters and layout of excavations is undertaken after granular flow experiment being carried out. Finally, several safety problems concerning induced caving are discussed resulting in countermeasures.Some of the conclusions made in this paper have been proved to be true by commercial tests. |
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