I. Geological overview of mining deposits and research on mining plan
North River marsh iron ore as a contact metasomatic skarn type magnetite beds, ore bodies located beneath the marsh north of the river bed, geological conditions and hydrogeological conditions more complicated. The main ore body Fe7 has a depth of 265.76~679m, a strike length of 1620m, a width of 92-376m, a maximum thickness of 160.68m, an average thickness of 44.9lm, an average TFe content of 51.04%, and a secondary ore body Fe6 burial depth of 285-476m. 360m, the maximum thickness of the ore body is 68.5m, the average thickness is 16.7m, and the average TFe content is 49.27%. The ore structure is mainly dip-dyed and block-like structure, the texture is relatively soft, and it is unstable to moderately stable. The roof is the middle limestone of the Ordovician Majiagou Formation, which is moderately stable to unstable; the surrounding rock is severely altered and has poor stability. The bottom plate is Yanshanian diorite , which is moderately stable. Between the ore body and the diorite, there is a layer of 5-10 m skarn alteration zone, which is extremely unstable.
According to the occurrence conditions of the ore body, the sub-column sublevel caving method is used for mining. The original design has a height of 60m in the middle section, a section height of 15m and a spacing of 12m. After cooperating with Northeastern University in 2001, the “four lows and one high†(low loss, low depletion, low cost, low accident risk and high production capacity) were proposed for the Beimuhe deposit conditions and the production experience of the Xingxing Mine Management Bureau. ) mining targets, designed for this refinement Sublevel caving, i.e. the ore is divided into a lead in the vertical direction, two parts, with a large structural parameters SUBLEVEL caving ore mining lower portion Inducing the upper part of the ore body to naturally fall. The falling ore is gradually received in the recovery of not less than three segments below. In the improvement scheme, the method of determining the structure and structural parameters of the stope is systematically analyzed and studied.
The bottomless column segmentation method affects the mining site structure parameters mainly by segment height (H), approach spacing (S) and collapse step (L). In order to improve the mining intensity, reduce the mining ratio and effectively control the mining site pressure, the current application of the sub-pillar-free sublevel caving method is to increase the segment height and the route spacing. The Beimuhe Iron Mine has adopted the optimization study to take the section height to 15m. This height is more suitable for the ore body conditions and mining technical conditions in the middle section of the first mining, but when it is beneficial to improve the ore moving space conditions, when determining the access spacing, In principle, the following two points should be considered: First, after the end of the section mining, the formed ore ridge residue (the shape of the residual ore formed by the approach) has only one peak, and the peak point is located in two In the middle of the road; second, the peak point reaches the mining port first when the lower section is mined. The former limits the approach spacing not to be too large, and the latter limits the reasonable spacing of the approach spacing.
In the stope structure of the diamond-arranged approach, each of the accesses is responsible for recovering one ridge residue, as shown in Fig. 1, the 14-way load recovers the ridge residual body A, and the 2 # access burden recovers the ridge residual body B. Moreover, in order to achieve the best recycling effect, each mining route should be able to completely recover the burden of the remaining ridges without disturbing the residual body of the adjacent ridges. Therefore, the boundary of the effective flow zone at the time of ore mining should completely surround the burdened ridge residue while not intersecting the adjacent ridge residue.
Figure 1 shows the method of determining the spacing of the route
It is experimentally concluded that the effective flow band width of the dispersion is:
(1)
In the formula, the α, β-vertical approach direction of the bulk flow parameter value; z-height direction coordinate value.
According to the relationship and expression (1) of Fig. 1, the calculation formula of the approach spacing can be obtained:
(2)
In the formula, the H-segment height, the b-path width, and the μ-factor are related to the exposed width of the waste rock funnel in the inlet top plate. The width of the Beimuhe iron ore mine is 4.2m, and the vertical flow parameters of the vertical approach direction at the end of the ore are: α-1.3221, β-0.5387. Substituting H=15, b=4.2, α=1.3221, β=0.5387 into equation (2), calculated:
(3)
Calculated by equation (3):
1 When using the non-depleted ore-mining method (μ≈0), the reasonable value of the approach spacing is 15.54;
2 When the cut-off grade mining method is adopted (μ≈0.75), the reasonable value of the approach spacing is 18.69;
3 When the low-depletion ore-concentration method is adopted (μ≈0.1～0.6), the reasonable value of the approach spacing is 15.96~18.06.
The Beimuhe Iron Mine adopts a low-poor ore-mining method, so the reasonable value of the approach distance should be between 16 and 18 m.
We use the loose-body flow parameters of the Beiganhe iron ore to carry out the simulation calculation of the ore-mining computer, and the change of the mining index with the distance of the approach is shown in Figure 2. It can be seen that in the range of the route spacing of 16 to 18 m, the ore recovery rate is high and the waste rock mixing rate does not change much. Therefore, the route spacing can be selected from any value in the range of 16 to 18 m. However, considering the advantages of improving the mining efficiency and preventing the ground pressure, the choice of the 18 m approach spacing is superior. For this reason, the Beishuihe Iron Mine is At a section height of 15 m, an approach spacing of 18 m was used.
Fig. 2 Simulation value of the relationship between the route spacing and the mining index
After the increase in the distance between the inlets, the residual body of the ore ridges increases, and the requirements for the recovery route are more stringent. In order to facilitate the production, the recovery route is set between the lowermost recovery tunnels, that is, the lowermost recovery tunnel is doubled, and the encrypted approach is used as a recovery route to fully recover the amount of minerals in the bottom plate. In addition, the first segment approach is placed inside the relatively stable ore body, and the space provided by the first segment approach is used to induce the natural rock from the upper ore and the roof surrounding rock. This resulted in a new large-structure parameter sub-column sublevel caving method (Fig. 3) that combines the natural fall of the Beihe River iron mine with the blasting caving.
Figure 3 The structure of the new scheme of the Beiyuhe Iron Mine
The mining sequence of the bottom-level approach of the new scheme is shown in Figure 4. The adjacent recovery tunnel is first recovered, and the recovery tunnel is then recovered (encrypted approach). For safety reasons, the lag-recovery distance of the recovery route should not be less than 3 to 5 collapse steps.
The recovery route is the lowest-level recovery route, and the amount of returned mining that it bears does not have the transfer condition, and the continuous moving space condition of the above-mentioned segmental transfer ore received by it is also natural at the end of the recovery route. It disappears, so that the ore that cannot be released from the recovery road becomes a permanent loss. Therefore, the recovery route adopts the cut-off grade mining method. As shown in Figure 4.
Once the segment height and the approach spacing are determined, the collapse step can be optimized. Since the actual shape of the ore body (falling body) after blasting is not easy to find out, the optimization work needs to be completed by on-site observation according to the actual mining phenomenon. According to the research results of the stochastic medium ore-mining theory, each particle trace has a certain position at the ore exit. According to the height of the first position of the waste rock at the exit, the waste rock can be identified along the trace from the front. Still the top. If the exposed part of the waste rock is low and surrounded by ore, it means that the waste rock comes from the front of the end. At this time, the step of the collapse is too small, and the step of the collapse should be increased; if the waste stone is “high†by the eyebrow of the mine The thin layer "flows out", indicating that the waste rock comes from the top surface. At this time, the step of the collapse is too large, and the step of the collapse should be reduced. The reasonable value of the step of collapse is to make the top and the front of the waste stone reach the mine at the same time. At this time, the waste rock is exposed late, and once it appears, it will occupy a large break at the exit. The area flows out at a faster rate.
Preliminary observations show that the Beiyuhe iron mine has a better position at the end of the mouth when the section height is 15m and the distance between the roads is 18m. To this end, the current Beiyuhe iron ore mine adopts a 3.7m collapse step, that is, two rows of blastholes are blasted once, the resistance line of the front row of blastholes is 2.0m, and the resistance line of the rear row of blastholes is 1.7m.
After the implementation of the natural structure and the blasting and caving of the Beiyuhe Iron Mine, the large-structure parameters of the bottomless sublevel caving method are reduced. The mining coefficient of the main mining area is reduced from 3.6m/kt to 2.07m/kt. in geological and hydrogeological conditions are more complex conditions, improved productivity, a year in advance to meet the design production capacity, creating a mine quickly reach capacity of precedent for the domestic large-scale metal; furthermore determine stope structure parameters as described above, and The low-depletion ore-mining method is adopted to better adapt to the flow characteristics of the caving rock, so that the ore recovery rate of the normal mining section reaches 92.5%, the ore depletion rate is about 11%, and good technical and economic effects are obtained.
Figure 4 shows the recovery sequence of the recovery route
Second, the conclusion
1. The new structure parameters of the natural structure and the blasting and caving combined with the bottomless sublevel caving method have reduced the mining coefficient and increased the production capacity. After the implementation of the Beihe River, good technical and economic effects have been achieved.
2. In the sublevel caving method without bottom pillar, the stope structure and the method of mining are to adapt to the movement law of the caving rock, in order to achieve the goal of low poverty mining.
3. The reasonable relationship between the section height and the approach spacing is related to the bulk flow parameters and the mining method. It can be calculated by the following formula:
4. The stepping distance of the collapsed ore needs to be gradually optimized according to the position and the exposed strength of the waste rock at the end of the end of the production. The Beiyuhe iron ore mine has a section height of 15m and an interval of 18m. The reasonable breakage step is 3.7m.
5. The problems concerning the shape of the collapse and the method of determining the step size of the collapse are to be further studied.
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