A sub-mining area of ​​the Dangping Tungsten Mine of the Jidongkeng Tungsten Mine is located in the southwestern slope of Jiulong Brain in the northern part of Dayu County, Jiangxi Province. The mine area has been using shallow hole retention method for mining. However, due to the complex changes of the veins, the parallel dense integration group, the frequent alternating faults and the local weathering of the surrounding rock, the problem of large mining loss rate has long plagued the mining operations of the mine.
To this end, in order to improve the mining process technology and reduce the loss of resources, the mine organized a survey on the occurrence and pulse rate of the veins in the area in the 1990s and 2000s. According to the survey data, there are a large number of parallel dense vein groups in this area. According to the principle of combined mining and mining, the “parallel dense vein group sub-mining mining method” was proposed.
Up to now, the middle section of the 500-370m area is being mined in the area. Except for some sections of the ore body that continue to be mined by shallow hole retention method, most of the parallel dense vein group ore bodies are mined by subsection mining method. The mining volume recovered by the section mining method accounts for nearly 75% of the annual mining volume.
Taking the mining method of section mining method between the 2-4 line parallel dense vein groups in the middle of 500m as an example, the process technology and economic effects of the “segment mining method mining parallel intensive vein group ore body” successfully applied in the mine for many years are analyzed and evaluated. .
1 Mine geological overview
The Jidongkeng mining area is located in the east-west complex structural belt of Nanling, and the tungsten-bearing quartz vein deposit is strictly controlled by fracture, and the structural fault is very developed.
The main faults in the area are F1, followed by F3~F10 faults. Among them, F1 is the largest fracture zone, the width is 27m, the trend is NEE, the tendency is SE, the inclination angle is 83°; the other faults are smaller, the trend is mainly NE, the tendency is NW, and the inclination angle is 70°～83°. Surrounding sandstone, sandy slate and slate; tungsten-containing ore is molybdenite, brass ore quartz vein. The ore is moderately stable, f=10~12, and the structure is complex and joint development.
The tungsten veins deposited in this deposit are divided into three groups: south, middle and north. The veins are dense and short, and the trend is 310°~320°, which tends to NE, and the inclination angle is about 75°. The average thickness of the veins is 0.19m, the average geological grade is 2.146%, and the pulse spacing is 2-7m, with an average of 4m. The three groups of veins are neither standard single veins nor large veins, nor typical fine veins, but sparse side curtains. Most of the veins are discontinuous single veins except for the complex veins composed of lenticular single veins that are closer to each other and larger in length. This discontinuous single pulse is between a few meters and a dozen meters apart in the horizontal direction or in the vertical direction. There are sparse veins between the two complex veins, and the morphological features of the veins are mainly characterized by the disappearance of the side, the enlargement of the enlargement, the branching and the reversion. At the same time, the veins are affected by the faults after mineralization, and the alternating faults are also frequent.
Application of 2-section mining method
For the Yandongkeng mining area, the characteristics of the deposits of the parallel dense vein clusters have been applied. Since the 1990s, the sub-mining mining method has been applied. Through the arrangement of cutting and cutting, such as sectional roadway, mining patio, sectional cutting cross-section, cutting patio, etc., in addition to facilitating safe mining and rock drilling, the complex changes of the veins in the horizontal and vertical directions are reliably obtained. Control, prospecting effect is good. Therefore, the sub-section mining method is to carry out the mining in the case of clear prospecting, which is one of the best solutions suitable for the combination of exploration and mining of parallel dense veins in the mining area.
According to the principle of demarcation of the mining area, before the implementation of the sub-section mining method, the calculation of the mining profit and loss grade of the mining block shall be carried out, and the mining boundary of the ore block shall be delineated accordingly.
According to the current market price, the profit and loss point of the mined ore grade of the 500m middle section 2-4 mining block is:
α Profit and Loss = C × β / (Y × ε) × 100% = (160 × 65%) ÷ (80000 × 84.5%) × 100% = 0.154%.
Where, C is the mining cost of the original ore of the enterprise, taking 160 yuan/t; β is the tungsten concentrate grade, taking 65%; ε is the ore recovery rate, taking 84.5%; Y is the sales price per ton of concentrate, taking 80,000 yuan / t.
The pulse rate of the circled ore was δ=0.154%÷2.262%=6.81%.
2.1 Subsection mining method
In the middle section of the 500m middle 2-4 line parallel dense vein group, the stope is arranged along the ore body, leaving no top and bottom columns, leaving only the column. The height of the stage is 40m, the height of the three sections is 14,13,13m, the length of the mine is 500m, the width of the column is 9.0m, the average mining width is 9.8m, the length of the bottom loading machine is 6.0m, and the spacing is 5~7m. . The section mining method is shown in Figure 1.

2.2 Mining and cutting engineering layout and mining operations

(1) Cutting and cutting engineering layout. A 500m mid-section 2-4 line parallel dense vein group is arranged at each end of the mining site with a mining patio, and a cutting patio is arranged in the center. According to the performance of the YGZ-90 medium-deep hole mining rig , a section of rock drilling roadway is drilled at a certain height (14, 13, 13m), and the bottom rock drilling roadway uses the original V38 along the pulse roadway. At the intersection of each section of the alley and the cutting patio, the vertical stopway is used to dig the cutting lane. At the bottom of the stope, the mine roadway is excavated in the upper and lower plates, and the mine lanes are excavated in the direction of the stope at intervals of 5 to 7 m.

(2) Mining operations. After completing the mining and cutting project, the YGZ-90 rock drill was used . In each section, the horizontal cutting of the flat roadway is drilled to the middle and deep hole, and the blasthole plum blossom type is arranged, and the resistance line is 1.0 m, thereby first forming the transverse cutting groove of the entire stope. Then, the fan-shaped middle deep hole is drilled in each section of the flat roadway, and the cutting groove is a free surface, and the back side is retracted from the center to the both ends from the top to the bottom. The effect of the medium-deep hole drilling rig is 40m/set, and the whole stope is drilled with a deep hole of 16150m.

The parameters of the medium-deep hole fan-shaped blasthole are: the minimum resistance line is 1.2-1.4m, and the hole bottom distance is 1.8-2.0m.
Medium-deep hole blasting adopts “detonating cord-detonating tube millisecond detonator double-type detonation network”, manual charging, segment-by-row blasting, and the charging coefficient is about 70%. The block rate is about 10%.
2.3 Subsection method mining main technical and economic indicators
For the 500m middle section 2-4 line segment mining method stope, according to the mining grade profit and loss point and the pulse rate of 6.81%, the mining width is 9.8m, and a total of 5 mining veins are returned, except for the V38 main vein. There are 4 secondary veins with a pulse spacing of 1 to 3 m, a total average pulse width of 0.84 m and a geological grade of 2.262%.
Mining quantity: Q mine = LHBr (1-ω) = 50 × 38 × 9.8 × 2.7 × (1-10.7%) = 44895t;
Where L is the length of the stope, m; H is the height of the mine, m; B is the mining width, m; r is the weight, 2.7t/m3; ω is the uncollected loss and the column loss, 10.7 %.
In the entire stope, the deep hole rock drilling footage is 16150m. Then, the amount of deep hole mining per meter is: 44895 ÷ 16150 = 2.78 (t / m).
The amount of gangue collected: Q pulse = 50 × 38 × 0.84 × 2.7 × (1-10.7%) = 3848 (t).
Depletion rate: ρ=(9.8-0.84)÷9.8×100%=91.4%;
It is concluded that the mining grade of the stope is: α mining = (1-91.4%) × 2.262% = 0.195% > 0.154%.
Loss rate of ore block: the loss of uncollected field and the loss of inter-column is Q loss = 462t, the loss of mining stop is 110t, the total loss of gangue is 572t, and the quarry of quarry is Q. =4309t. Therefore, the total loss rate of the stope is: ρ total = (Q loss / Q mining) × 100% = 13.3% (where the loss of mining is 2.6%).
The amount of metal recovered: this sub stope mining method capable of recovering an amount of metal of metal Q = 3848 × 2.262% × (1-2.6 %) = 84.78 (t).
Mining ratio: K = (ΣL÷Q pulse) × 1000 = (446÷44895) × 1000 = 9.93 (m / kt).
Explosive unit consumption: Explosives are Φ45mm ammonium nitrate columnar medicine (medicine length 300mm, each medicine weight 0.5kg), total construction depth of 16150m, the total explosive dosage is: 16150m × 70% ÷ 0.3m × 0. 5kg=18842kg. The unit consumption of medium-deep hole blasting explosives is 0.42kg/t. Another secondary crushing requires the consumption of explosives: 44895t × 10% × 0.42kg / t = 1886kg, in the formula, the mining block rate is 10%. The total explosive consumption of the mining site is 18842kg+1886kg=20728kg. Then, including the amount of secondary crushing, the total consumption of total explosives in the entire stop mining is: 20728kg ÷ 44895t = 0.462kg / t.
Direct cost of mining: Calculated according to the current market price, rock drilling tools of 142,400 yuan, blasting equipment of 316,600 yuan, feng shui power consumption of 248,700 yuan, precision cutting costs of 557,500 yuan (total amount of engineering 446m) ), the wages of workers are 121,200 yuan, and the total direct cost of mining at the end of the mining stop is 1,386,400 yuan. The direct cost per ton of ore is: 138.84 million yuan ÷ 44895t = 30.88 yuan / t (including the mining unit mining cutting unit cost 12.42 yuan / t).
2.4 subsection mining method evaluation
(1) The subsection mining method overcomes the shortcomings of the shallow hole retention method, the mining area of ​​the intensive ore body is too large, the operation is unsafe, and the clamping wall is difficult to maintain. If the ore block is mined by shallow hole retention method, only the V38 main vein with a pulse width of 0.40 m can be recovered, and there are 0.24 m in-situ veins and 0.2 m off-site veins cannot be recovered. Therefore, the segment mining method is the most likely to recover resources, and has achieved better economic benefits than the shallow hole retention method.
(2) In view of the occurrence characteristics of the parallel dense vein clusters in this area, based on the investigation of the mining loss rate of the shallow mining method in the 50 sections of the two sections of 538,500, the loss rate of the mining block is 31.6%. Among them, the top, bottom and inter-column loss of the stope is 8.2%, the loss of ore discharge is 10.2%, and the mining loss is 13.2%. With the segmentation method mining, the total loss rate of the stope is reduced to 13.3%.
(3) Sectional mining method Rock drilling and blasting are all carried out in the sectioned roadway, which overcomes the safety hazards such as the roof slab and the suspended space caused by the shallow hole retention method directly entering the mine operation.

(4) According to the annual production scale of 100,000 tons, 3 stopts can meet the annual production demand of the mine, thus reducing the number of ore blocks and the time pressure for the preparation of the ore blocks, increasing the potential of the mine production scale, and facilitating Mine production management.
(5) The application of the sub-section mining method, the shallow hole retention method reduces the mining-production ratio by 18.77m/kt, which saves the engineering cost; the explosive unit consumption is reduced by 0.238kg/t compared with the shallow hole retention method. The direct cost of mining was reduced by 33 yuan / t. According to the annual production of 100,000 tons of ore, the mine can save mining costs of 3.3 million yuan per year.
(6) It has been more than 20 years since the first application of the sub-mining method in the middle section of the 500-series mining method. It has been used in the case of shortage of mining industry workers, and it has been safely exploited by the sub-section mining method of 500-370m. Nearly 60 stopes in the middle section. Due to the reduction of mining losses, the mine production service life has been greatly extended, and the social and economic benefits are significant.
(7) For the shortcomings of the large-scale depletion rate of the sub-section mining method, in addition to increasing the waste-discharging process in the hand-sliding wells, the pulse rate of the mining block is increased as much as possible, and the reasonable mining rate is the main means to reduce the depletion. There is also a need to further improve the process structure and mining techniques of the subsection mining method.
3 conclusions
For the Jidongkeng mining area, the vein is neither a standard single vein, a large vein type, nor a typical fine vein belt, but a complex feature of the sparse side curtain type, which is reduced by the application of the subsection mining method. Mining costs, reducing production safety management risks, increased resource recovery rates, thereby extending mine service life.
references:
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[5] Editorial Board of Mining Manual. Mining Manual (Vol. IV) [M]. Beijing: Metallurgical Industry Press, 2008.