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Bottomless column caving method
1) Distance of mining roadway——In mine production, the distance of mining roadway is generally 8~12 meters, which is slightly less than or equal to the height of one section. There are many mines (e.g., iron ore temple) 10-m spacing. The spacing of the mining roadway is too large, too small is not suitable.
1 From the perspective of ore mining, when the distance of the mining roadway increases, the ellipsoids of the adjacent two mining roadways are not tangent, and the ore loss is increased. (Separation of two ellipsoids)
The distance between the entrances ↑→the amount of roadway excavation engineering→the stability of the roadway→the ore loss↑.
2 Two ellipsoids intersect. When the ellipsoids B and C intersect, when the ellipsoidal ore is released, the ore of the ellipsoid C is placed, and A is already a waste rock, and thus the depletion increases.
The road between the roads → the roadway excavation project → the roadway stability ↓ → the ore depletion rate ↑.
3 When the two ellipsoids are tangent, it is also the choice of the spacing of the two mining roadways. The loss and depletion indicators are better. It can be seen that in determining the spacing of the mining roadway, the relationship between the release of the ellipsoid shape and the depletion index should be considered.
When the ore is stable, the spacing of the back roadway mainly depends on the ore loss index of the ore.
In addition, when the ore of the caving ore is too much, wet, and the fluidity is poor, the spacing of the mining roadway should be smaller.
2) Cross section size of mining roadway
1 The size of the section of the mining roadway depends on the ore and stability, and the selected mining and rock drilling equipment. If ZYQ-14 loader and CEE-700 rock drilling rig are used, the access section can be width × height = 3 × 3 or 4 × 3 m 2 .
2 The section of the mining roadway is related to the ore flow law during the mining.
(i) Route width – from the perspective of reducing the depletion of ore losses, the approach is wider. The widening of the road and the loading equipment can be loaded on the full width of the roadway, so that the ore rock is lowered at the horizontal contact surface, which can improve the ore recovery index. Therefore, when the ore is stable, the access is wider.
(ii) Height of the mining approach – from the point of view of the mine, the approach height is small. Because the height of the roadway is large, the upper waste rock will be mixed into the ore in the approach in advance, so that the frontal loss in the approach is increased. The frontal loss is difficult to recycle. (Not to mention the positive loss has a considerable proportion)
In general, the access height is about 3 to 3.5 meters.
3) Cross-section shape of mining roadway
The cross-section shape of the mining roadway can be either rectangular or arched. From the perspective of mining, the rectangular section is better than the arched section. Because the arch of the arched roadway is higher, the narrower the ore flow surface is, the more likely it is to block, and the ellipsoid is elongated and the ore loss is increased.
From the perspective of the stability of the roadway, the arch shape is better than the rectangular shape. Therefore, when the stability of the ore is poor, when the arched section is to be used, the spacing of the mining roadway should be appropriately reduced.
4) Arrangement of mining roadway
Can be divided into two types of layout along the strike and cut. When the thickness of the ore body is large, (≥15~20 m), the approach can be cut to the direction, and vice versa. (Damu Iron Mine is cut to the direction of >20 meters.)
When arranging along the strike, the mining roadway is arranged as close as possible to the lower plate, so that the ore layer can be diamond-shaped to collapse. Thereby reducing ore losses.
Pay attention to the layout of the mining roadway:
1 Slope requirements - In order to facilitate the drainage of the mining roadway, the shipping equipment is heavily loaded downhill. Therefore, the slope of the roadway should be 3-5% of 0.
2 Turning radius requirements—There is a turning corner in the mining roadway. For the convenience of loading and loading equipment, it should have a large radius of curvature.
The general turning radius is R>12 meters.
3 The mining roadway of the upper and lower sections shall be arranged in a diamond shape.