| In underground mining of metal mine of China,there are about 20%steeply inclined medium thick orebodies.With the increase of mining depth and the production of hard-to-mine ore deposit,steeply inclined medium thick orebody ratio will be further increased.Therefore,it is significant how to mine them safely and efficiently to improve the recovery of mineral resources.In this paper,we use three-law efficient and well adaptable mining theory that rock mass falling down law,granules flow law,geostatic activity law,to study systematically drift induced caving mining technology of steeply inclined medium thick broken orebodies,and to develop new ways to difficult mining orebodies.First,the minimum width of drift induced caving methods are studies with arching experiment based on the analysis of the easy-caving character of ore-rock mass and the process of caving.And then the applicable conditions are analyzed and established.Secondly,structures of the stopes along with following-vein drifts to induce and recover ore rocks are proposed and so are the methods to delimit induced falling area and forced one and to choose structural parameters of induced engineering based on characteristics of granular flow.Third,the quantitative relationships between the position of following-vein drift and mining index are studied with the experiments,determining the reasonable positions of following-vein drift in different angles of dip for the steeply inclined medium thick orebodies.Fourth,some technologies are given to restrict the caving of hanging wall,deal with large ore in excavating area,and recover retention ore rocks.And then the advancing and supporting technology for working faces and soft broken rock mine excavating drift are also given in order to make sure that drift induced caving method is going on well.The drift induced caving method proposed in this paper was applied in the north ore area of Jianlong Shuangyashan iron mine.The cutting roadway,the broached groove of oblique blastholes and both ends of the retreat mining of the drift induced caving method have been proposed.No.S3 and S5 stopes were selected for testing at 170m level.Aiming at the conditions that there is a large amount of residual ore at upper level and medium-sized goaf in No.S3 stope.Firstly,we adopted transverse drifts to claim residual ore at upper level.On the basis,according to S3 and S5 test stopes conditions,the structural parameters were analyzed and the mining process of drift induced caving method were designed.And then based on S3 stope goafs locations and the easy-caving characters,a measurement to resolve mined-out areas is proposed that induce the ore rocks to falling at the side of mined out areas.By tracking and observing the conditions of test stopes,we found that the size of boulders were great and when the roofs were falling,mixed rock ratios rose with fluctuations and ranges of variation were related to exposed boulders.We also found that the speeds were related to the locations of drifts.If the location of drift was not good or the bulks were stuck,the mixed rock ratios were strongly affected.Charging vehicle were used in later period,blasting effects were significantly improved.To S3 and S5 deposits,it means a better extraction index.The theoretical analysis and practical application showed that drift induced caving method is flexible,security,economic and the like,and is effective to solve the problems of mining steeply inclined medium thick broken orebody.The method is one of simple and highly efficient mining methods because it focuses on the broken characteristics of orebodies,reducing work volumes of stopes,which is suitable for low-grade and difficultly-mined broken orebodies and can achieve the goal low cost and high efficient mining. |
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