Big chestnut iron ore mining and mining method

Big chestnut iron ore Eastern sedimentary metamorphic iron ore deposit. Since 1970, the No. 6 and No. 6-0 ore bodies have been mainly mined. The two are parallel, with a length of 100-150 m, a thickness of 6-15 m, a dip angle of 30°, and a grade of 30-48%. The ore is moderately stable, and the surrounding rock of the top and bottom plates are all marbles , which are moderately stable. Only the direct roof of No. 6 ore body is 0.2 m thick phyllite. It is mainly mined by the method of retention. The mine is 30 to 50 m long, the top column is 4 m high, and the bottom column is 6 to 8 m high. Since 1979, attention has been paid to the recovery of pillars. In 1980, the amount of ore produced from the top and bottom columns reached 79.8% of the total ore produced in the area. There are empty areas around the top and bottom columns, and there are some falling rocks. In the past, the use of medium and deep hole mining top and bottom columns, due to unclear boundaries, improper design and construction of blastholes, not only the ore depletion and loss during blasting, but also large blocks, difficult to mine, most of the ore did not release the roof The recovery rate is extremely low. Later, the mining method was used to recover the top bottom column (Fig. 1). In order to ensure the safety of the operation, the following mining sequences and measures are adopted:

(1) The top and bottom columns are divided into small slits along the strike direction, and the strips are successively collected in the backward manner. The vertical direction of the striping is recovered from the bottom to the upper disc (or vice versa), and the exposed area is generally controlled at about 50 m;

(2) The mining layer is 2m high and mines with horizontal blastholes. The last layer is 3m high. If there is a waste rock in the upper part, leave a 1m thick ore, and as the ore is released and the suspended roof distance increases, the ore will naturally fall and the working surface pressure will be reduced;

(3) Strengthen the working face support with rafters and columns. Using the above measures, a large number of ore were produced in a few years without casualties, the recovery rate was 67.3%, the depletion rate was 10%, and the recovery rate was increased by 20 to 31% compared with deep hole recovery.

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