The mine is located 80.5km west of Denver, Colorado, USA. The mine ground industrial facility is on the east side of the continental watershed, and the plant is built on the west side. The ore is transported to the plant through a 15.5km long flat at 7500 main transport level. Construction in 1967, completed and put into production in 1976. The upper 8100 production level design is 27,215 tons of ore per day, and the lower 7700 production level is designed to produce 31,751 tons of ore per day. Currently produced at the upper level. The mine employs about 2,000 people.
(1) Geological overview. The deposit is 1200m deep and is a reticulated molybdenum deposit with a reserve of 303 million tons and a MoS 3 grade of 0.49%. The deposit is endowed with a Tertiary rhyolite porphyry intrusion into the Precambrian granite . The ore body formation and collapsibility are shown in Tables 1 and 2.
Table 1 Technical conditions for mining of natural caving method in foreign application stage
country | Mine name | Mining method | Deposit type | Ore body morphology | Ore inclination |
United States | Clemex Molybdenum Mine (Climax) | Overall continuous collapse, embers mining | Reticulated vein molybdenite | The section is in the shape of a circle, and the plane is oval. | |
United States | Henderson Copper Molybdenum Mine (Henderson) | Overall continuous collapse, scraper mining | Reticulated vein molybdenite | The cross section is serpentine and the plane is elliptical | |
United States | Longrad Molybdenum Mine | Continuously falling all day, electric shovel mining | Reticulated vein molybdenite | Oval vertical column | |
United States | Questa Molybdenum Mine | The mass of the nugget collapses | Molybdenite | Horizontal tubular | |
United States | St. Manuel Copper Mine | The mass of the nugget collapses | Dip-like porphyry copper-molybdenum ore | The section is inclined U-shaped and the plane is semi-elliptical | The southern ore body is steep, and the northern ore body is about 50°. |
United States | Grace iron ore | Overall continuous collapse, scraper mining | Massive magnetite | Waist shape | 30° |
Chile | Eltnent Copper Mine | The ore collapsed, the grid sieved out of gravity (secondary mine); the panel collapsed, the scraper demineralized (primary mine) | Massive sulfide copper ore | Columnar | steep |
Chile | El Salvador Copper Mine | The mass of the ore collapses the grid gravity, the embers and the scraper mine | Porphyry copper deposit | | steep |
Canada | Satford Asbestos Mine | The nugget collapses and the scraper mines | Igneous network asbestos vein | The plane is oval | steep |
Philippines | St. Thomas Copper Mine | Nugget collapse | Dip-dyed brass deposit | The section is tubular and the plane is oval | 80° |
South Africa | Dipie Diamond Mine | Panel collapses, embers are mined | With diamond brecciated mica | | |
Unfinished, see continued table 1 [next]
Continued Table 1
country | Mine name | Ore body size (m) | Ore body caving characteristics |
Go | thickness | Vertical height | RQD (%) | Joint density (bars / meter) | Compressive strength (MPa) |
United States | Clemex Molybdenum Mine (Climax) | 1219 | 250 | 420 | 40~70 | 8~11 | 34.3~109.8 |
United States | Henderson Copper Molybdenum Mine (Henderson) | 914 | 671 | 185 | 47 | 6.6 | 123.6~130.4 |
United States | Longrad Molybdenum Mine | 360 | 120 | 300 | 50 | 3 | 117.7~127.5 |
United States | Questa Molybdenum Mine | 1524 | 122~244 | 122~244 | 15 | >100 | weak |
United States | St. Manuel Copper Mine | 1500 | 30~300 | 600 | 30~40 | 13 | 98.1~132.4 |
United States | Grace Iron Mine | 360 | 90 | | From very broken to very strong | |
Chile | Eltnent Copper Mine | 1800 | 400~700 | 700 | 0~50 70~100 | 15~90 0.5~3 | 98.1~117.7 |
Chile | El Salvador Copper Mine | 1370 | 914 | 50~213 | From very weak to very strong | |
Canada | Satford Asbestos Mine | 457 | 244 | 366 | 59 | | |
Philippines | St. Thomas Copper Mine | 330 | 210 | 1000 | Good caving and fracture | |
South Africa | Dipie Diamond Mine | 900 | 450 | | | | 175 |
Table 2 Rock fragmentation characteristics of some mines in the natural caving method at the domestic and international application stages
Mine name | Number of joint groups | Joint density (bars / meter) | Complete rock block compressive strength (MPa) | RQD (%) | Cavitation index | Initial pull-down area (m 2 ) | Original rock stress (MPa) | Capacitability description |
Level | vertical |
Jurad Molybdenum Mine | 3 sets of steep joints without horizontal joints | 3 | 117.7~127.5 | 50 | 7.5~8 | 14214 | 10.0 | 18.0 | Difficult to collapse |
Clemex molybdenum mine | More than 3 sets of joints have horizontal joints | 8~11 | 34.3~109.8 | 47~70 | 3~5 | 122×122 | 7.0~8.0 | 11.0~13.0 | Easy to medium collapse |
Henderson Copper Molybdenum Mine | 2 sets of steep joint level joints are not obvious | 6.6 | 123.6~130.4 | 47 | 6 | 120×180 | 29.0 | 30.0 | Medium collapse |
St. Manuel Copper Mine (San Manuel) | 3~4 sets of joints have horizontal joints | 13 | 98.1~132.4 | 30~40 | 5~6 | 40×60 | 140.0 | 112.1 | Easy to collapse |
Eltnient Copper Mine (primary mine)
(El Teniente) | 2 groups of steep joint levels are not developed | 0.5 | 98.1~117.7 | 70~100 | 7~10 | | 40.0 | 39.0 | Hard to collapse |
Lakeside Copper Mine (Lakeshore) | Extremely developed | 25.6 | 2.0~147.1 | 15 | 3~4 | 30×30 | 7.0 | 6.0 | Easy to collapse |
Zhongtiaoshan Nonferrous Metals Co., Ltd. | 2 sets of steep joint level joints are not developed | 6 | 73.5~147.1 | 70 | 7~9 | 120×133 | 11.8 | 4.9~5.9 | Collapse |
[next] (2) Appropriate layout. The ore body is divided vertically into three main stages of production (Figure 1). The stage is 122m high and has two main mining stages and one main transportation stage. The three main stages are connected to the shaft, and the various levels of each stage are connected by ramps.
Figure 1 Mining stage and production levels
1-8155 bottoming level; 2 - upper 8100 production level; 3-8050 inlet level;
4-8035 return air level; 5--lower 7700 production level; 6-7500 main transport level; 7-mining runway
There are six levels in each stage of mining; the level of the bottom, the two levels of weakening (44.2m and 62.5m above the production level, respectively), the level of production, and the level of incoming and return air below it. [next]
It is divided into three panels along the main axis of the ore body on the plane, with a width of 244m and a length of ore body thickness. There is no pillar left in the disk section. A panel can take 7 to 10 years. The vertical ore body is digging into the scraper road every 24.4m; the excavation path is 12.2m from the scraper road at a horizontal angle of 12.2m (see Figure 2), in the corresponding two outbound approaches. The middle is excavated by the mining funnel. The ore-draining well is arranged on the side of the scraper, and one is arranged every 97.5m or 8 ore points. Two adjacent ore branch slides are combined to form a straight through-transport level.
Figure 2 Scraper tapping system
1-Scraper road; 2-loading approach; 3-flat bottom V-groove; 4-draw roadway; 5--mining trench blasthole;
6-lower blasthole; 7-mining runway; 8-transport roadway; 9-return airway roadway; 10-return airway; [next]
(3) Pulling the bottom. Drill the roadway parallel to the scraper road at 16.8m directly above the scraper track. The annular deep hole is drilled from the bottoming roadway, and the annular blastholes of the adjacent roadway are arranged offset from each other, the spacing is 2.1m, the aperture is 76mm, the hole depth is 18m, and there are 23 annular holes in each row (see Figure 2). The blasthole below the horizontal line (thick line) is blasted to form a sulcus, and the upper blasthole forms a bottoming space after blasting. The annular blasthole is filled with blasting, first blasting the deep hole below the horizontal line, and then blasting the deep hole at the bottom. When blasting the annular blasthole, the V-groove must be excavated in the middle of the cross-over road in the middle of the mining approach. The annular blasthole is blasted 3 times at a time, and is carried out in the order of advancing with the collapse line. In order to avoid stress concentration damage to the scraper path and the outflow port, efforts should be made to make the collapse line an optimal step-like advancement. The distance between the two adjacent bottom roadways is controlled to be 6~12m.
(4) Weaken the project. The weakening of the ore body boundary is to form a cutting sump or a crack surface by drilling a vertical deep hole blasting in the roadway. In the initial caving phase, the first, second and second layers weaken the deep holes with a diameter of 76 mm from the weakened roadway, and the hole spacing and the row spacing are both 1.5 m. After the blasting, a continuous cutting groove is formed. The third layer weakening is to drill the 18m deep upper vertical deep hole from the uppermost layer, and the hole spacing is 1.5m, and the pre-cracking surface is formed after blasting. After the collapse is normal, the three layers can be weakened by pre-cracking, and only the local groove can be made at the corner.
(5) Support for mine roadway. Both the scraper roadway and the mining roadway are supported by 305mm thick concrete, and the eyebrow line is reinforced with steel beams. When the collapse line moves through the production area, the concrete supports are reinforced with anchor bolts and repaired with shotcrete.
(6) Mining. With a 3.8m 3 diesel scraper, the maximum transport distance is no more than 49m, each scraper is responsible for 9 to 12 mine discharge points, with an average efficiency of 816 tons / shift. Under normal circumstances, there are 320 mine discharge points that can be mined. A block size of less than 1.2 m is a qualified block degree. The large block is broken by rock blasting or hydraulic breaker, and the card funnel is treated with a special rock drilling rig. Secondary blasting is not always possible even in the early stage of mining.
The mine-mining engineer releases the number of buckets for the discharge of the scraper to each mine release point every day. The total amount of ore and ore grade released by each ore point is controlled by a computer. Each time a 907t ore is released, a sample is taken at the ore point to determine the ore grade. At the end of the mine release, the sampling interval is reduced to 91t, which is sampled once, so that the cut-off grade of the discharge point can be determined in time.
The ore-mining engineer balances the rate of ore discharge and the rate of collapse, which is about 0.3 m/d. In order to minimize the depletion, the ore contact surface maintains a 56° inclination angle. For this reason, from the collapse line, the allowable ore discharge per discharge point is increased by 15% of the ore-bearing amount.
(7) Ventilation. A push-in extraction hybrid ventilation system is used. The fresh air is pressed into the well from the 3 #风井, and enters the scraper path from the inlet air level through the wind shaft. The dirty wind is discharged to the return air level through the branching well of the ore discharging well, and then the surface is extracted from the 1 # wind well by three exhaust fans. [next]
The main technical and economic indicators are shown in Table 21-29.
Table 3 Main technical and economic indicators of natural caving method in foreign mine application stage
Mine name | Production scale (t/d) | Labor productivity (ton / work class) | Secondary crushing explosive unit consumption (kg/t) | Ore recovery rate (%) | Ore depletion rate (%) |
Underground production workers | Full mine |
Klemax Molybdenum Mine Henderson Copper Molybdenum Mine Questa Molybdenum Mine St. Manuel Copper Mine Grace Iron Mine Eltnient Copper Mine (Secondary Mine) El Salvador Copper Mine Satford Asbestos Mine St. Thomas Copper Mine Dipie Diamond Mine | 48000 28000 13600 55000 10000 62000 26000 4080 21000 5.3 million tons / year | 200 58.7 34~45.3 73 72 54.67 twenty four | 31 31.8 17 36 45 17~20 14 6.5 | 0.23 0.023 0.454 0.01 0.272 0.249 0.09 | 92.5 96 97 101.5~134.4 85 90.95 100 100 | 15 15 20 12.2~14 20 10~20 20 20 |
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