(1) Geological overview. Mine is located in northeastern Arizona, Tucson, about 72km, it is a Magma copper companies. It was put into operation in 1956, with a design capacity of 35,000 tons/day, and has recently expanded to 65,000 tons/day. The deposit is characterized by a large low-grade disseminated brass deposit in a two-long porphyry with weak structure, fracture and strong alteration. The ore body is inclined U-shaped on the section. The upper ore body is divided into two branches, north and south, respectively called the south and north ore bodies. The south ore body is the main ore body, which is steeper and has a depth of more than 600 meters; the north ore body has a dip angle of about 50°. The ore body has a length of 1500m and a thickness of 30-300m. At the top of the ore body, there is a relatively strong and difficult-to-crack Tertiary breccia cover with a thickness of 9-610m. As shown in Figure 1.
Figure 1 Section of the St. Manuel ore body
1-oxidized ore; 2-mixed ore; 3-sulfurized ore; 4-conglomerate [next]
The main ore rocks are two-long porphyry and quartz monzonite, which have joint development and good collapseability. The joint fillings are mainly clay and chlorite, and the joints are mostly open. The Tertiary breccia is relatively strong and tends to become large when it collapses. The ore body collapse characteristics are shown in Table 1.
Table 1 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 |
In the mountains of non-ferrous metals mining company Tongkuangyu | 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 |
(2) Appropriate layout. The height of the stage is 183m. Due to the gentle inclination of the ore body, a section is added between the main sections, and the section height is 91m. The mine used the checkerboard type of ore mining, the double-block interval recovery and the double-diagonal diagonal retreat, but they were all stopped due to excessive ground pressure. At present, the horizontal size of the first nugget in the sub-panel is generally not less than 64 × 42.7 m to ensure that there is enough horizontal pull-down area to promote initial collapse. There are three levels in each mining stage, and the lowest level is the transportation level. The upper level is 18.3m, and the upper level is 4.6m. The circular transportation system is installed in the roadway, and the distance between the tunnels is 21.35m, and there are two lanes in each lane, which are respectively driven into the centerline position of the half panel. Some of the tunnels are connected to the roadways along the veins, while others form a single head. The latter are connected to each other by a wind bridge for ventilation and safe entrance and exit, as shown in Figure 2. In the grid horizontal vertical ore body excavation panel roadway, the center distance is 85.4m, each serving two panels. The ore-boring wells and branching wells are excavated at a slope of 63° every 10.7m in the tunnel of the vein-transporting lane, and the gridway is arranged along the ore body at a distance of 10.7m, which is 42.7m long. The funnel spacing is 5.33m and the bucket neck is ф1.52m. Dig the contact roadway in the middle of the two panel roadways, and connect the grid roadway for ventilation and safety exit, as shown in Figure 3.
Figure 2 2075 horizontal transport system layout [next]
Figure 3 gravity mining
1-Transportation roadway; 2-minening chute; 3-branch chute; 4-grid roadway;
5-funnel; 6-pull roadway; 7-pull hole; 8-way
(3) Roadway support. The roadway along the vein is supported by a 300×300mm wooden shed, and is reinforced with cross braces at the vault and column foot. The stability of the rock is poor and the area close to the production area is supported by arched steel brackets and watered with 450-600 mm thick concrete. All the roadway lanes are supported by wooden brackets or steel brackets and concrete supports. The grid floor of the grid is supported by 450m thick concrete, and when it is deep, it is reinforced with wooden brackets or steel brackets. Each lane serves 3 to 4 years. All the grid roads are filled with concrete, the side thickness is at least 450mm, the top is 600mm thick, and the bucket is reinforced with 200mm wide wear-resistant steel beams. The grid roadway has an average service of 1.5 years. The ore-boring and branching wells are supported by wooden frame brackets, and the wear-resistant high-carbon steel plates are nailed on the wooden frame brackets, and the net section is 1.2×1.2 m. The monthly concrete consumption of the mine is 4600-5400 m 3 . [next]
(4) Pulling the bottom. The distance between the bottoming lanes is equal to the funnel spacing, supported by wooden sheds, shallow holes are pulled, and a funnel distance is blasted each time.
(5) Mining. To meet the production of 55,000 tons / day, an effective bottoming area of ​​56,907 m 2 is required, and about 2000 concentrating funnels. The average ore-mining speed of each concentrating funnel is 0.45-0.61 m/d, that is, 32-45 t/d. The mine geological department makes a sectional view of each discharge ore funnel, indicating the ore layer height, ore content, grade, and type and grade of the rock causing depletion, and calculates the ore and grade of the entire ore block. According to the prospectus, the production requirements and the number of nuggets that can be produced (about 22 production nuggets per day), the ore-mining engineer assigns weekly production quotas and mining units to each production block, and prepares the mining instructions. It is sent to the mine squad leader every day. Each shifting squad leader fills in each of the concentrating funnels and actually releases the ore amount of the ore mining engineer into the computer. Samples were taken by a miner, analyzed by X-ray fluorescence fast analyzer, and the results of the grade analysis were also entered into the computer. When the cumulative release of ore and grade reports indicate that the ore hopper is nearing depletion, it should be encrypted and sampled. The three consecutive grades are lower than the cut-off grade, and the ore-mining engineer issues a stop-mining instruction.
(6) Ventilation. The design air volume is 11327m 3 /min, and the wind is taken from the No.1, No.4 and No.5 auxiliary wells, and then the main stone gate and the ventilation stone gate of the transportation and grid level are respectively entered into the grid road and the transportation lane. The filth level of the filthy wind is discharged to the surface of the mine through the ore-draining or return air patio to the surface level through four main transport lanes.
The ventilating block uses 15kw high air volume, ground pressure, low speed fan fan, single working place and heading face to ventilate with high pressure high speed fan fan of 7.5kw and 15kw.
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