| Yanqianshan iron mine belongs to Anshan Iron and Steel Group Corporation which is in the transition period turned from open-pit to underground mining. The company current production is2.5million t/a. Open-pit mining is expected to end in early2012. After open-pit closed down, the production of transition period will mainly be from end-slope ore body mining. Design uses sublevel caving method without sill pillar. At present the preparatory construction of first sublevel of both east and west end-slopes have been completed. The first sublevel of west end-slope from the surface is53to114m and the first sublevel of est end-slope from the surface is35to106m. Initial mineral reserves are more than about5.5million ton. In order to ensure production safety and realize the goal of increasing cohesion transition period, the company and Northeastern University cooperate to profoundly research on high-efficient mining techniques.First, through the field geological survey and point load strength tests, the stability of rock mass is classified and the conclusion is gained that both east and west end-slopes are of good caving ability. Then, analyzing the ability further based on the results of the classification of rock mass, we calculate the vaules of critical span and area of of caving. Finally, according to the above research conclusions and the present development of mining engineering, the proposal is presented, namely "induction caving method for ore body at end slope". It is implemented to control the process and sizes of caving by adjusting the area vaule of the roof and the types of mined-out stopes, which eventually makes overlying rock body reach the earth surface and recovers caving ore rocks in the two lower levels of drifts.Using the proposed scheme, ore rocks are not only able to recover about5,5million ton above the first level but also reduce the engineering quantities of preparation, the cost and the steps of production and improve the intensity and output of mining. At present, This project has been accepted and applied in Yanqianshan iron mine, and has entered the stage of construction. |
