Study On Stable Transition From Open Pit To Underground Mining In Yanqianshan Iron Mine

The transition from open pit to underground mining is a trend of deep open-pit mining, this paper has over-all discussed the techniques on the transition from open-pit to underground mining, and connected with the actual conditions, studied on the stable transition from open-pit to underground mining of Yanqianshan Iron Mine. The appropriate mining system is probed, meanwhile adopt the key technique to attain the stable transition, which mainly include:the first strata, which is used to make sure the stable production, does not stay the pillar in the bottom of open-pit, and stay the ore bedding cushion, its thickness is 10m, which shortens the time of making capping and enlarges the production ability of the first strata; the side slope's ore adopts the mining technology of "strong driving, strong mining and strong extracting", the mining method make up for the production lack in the last year from open pit to under ground mining, and create the condition for the first year production in the underground mining; in order to make up for stable transition in time, we strictly follow the key line to construct the sinking and driving engineering, and finish the anticipational the ore production of development work and preparation mining; the process of making capping can not influence the normal production in the open-pit and the driving in the underground mining, the making capping adopts the abandoned rock in the open-pit, which meets the need of production technology in the underground mining, winter protection and flood protection. Otherwise, the disadvantage factors which influence the transition from northern open-pit to underground mining has been analyzed. By studying on the arrangement plan of roadway, the driving subsequence, the mining stopping subsequence and the absorption of vibration in the open-pit blasting, and adopt the advantage method to lessen the stress concentration in the open-pit slope and the failure of underground roadway; according to the character of northern climate, we adopt the ventilating method of the drawing and pressing multilevel station, lessen the negative pressure of stopping, and attain the winter protection; adjusting the stopping sequence, we apply the impound pit created by the initial stopping step to settle up the drainage in the underground stopping.By studying on the upper questions, we master the key influence factors of the transition from northern open-pit to underground mining, attain the stable transition, and shorten the transition period. The results will give other iron mine of Anshan Iron and Steel Co. Ltd., from open-pit to underground mining for some references.