Chinese copper mine since 1954, has been in this mining method as the primary mining method. The mine is a contact-deposited skarn type deposit. The majority of the ore bodies are discontinuous small isolated ore bodies. The vertical height of a single ore body is generally only 10-15 m, a few of which are 150 m; the strike length is generally about 15 m, and the individual length is 200 m; the thickness is generally 5-20 m; . The shape of the ore body is very irregular, the upper inclination angle is relatively large, generally above 65°; the lower inclination angle is relatively slow, generally 40° to 65°. The ore body is in close contact with the surrounding rock. The upper plate is dolomitic marble and the lower plate is granite , which is very stable. The ore is stable. Because the deposits are mostly short and small blind ore bodies, the height of the stage is 30-40m. Experience has proved that the exposed area of ​​the roof of the mine should not exceed 400m 2 and the span should not exceed 12m. If the span exceeds 12m, even if the exposed area of ​​the roof does not reach 400m 2 , it is not safe. Therefore, when the thickness is less than 12 m, the nuggets are arranged along the strike, as shown in Fig. 1; when the thickness exceeds 12 m, the nuggets are arranged vertically, as shown in Fig. 2.
Fig.1 The structure of the bottom structure of the electric ramp arranged along the strike
1-stage transportation roadway; 2-return roadway; 3-electric roadway;
4-minening well; 5-bottom column; 6-top column; 7-column
Figure 2: The vertical structure of the electric ramp bottom structure retention method
1-Transportation lane; 2- return airway; 3-electric roadway; 4-minening well;
5-Pedestrian well; 6-bottom column; 7-top column; 8-patio; 9-contact
When a single ore body divides several ore blocks along the strike, a column of 10 to 12 m wide is left between the mine houses. In most ore bodies, the bottom column can be left without the bottom column, and the bottom structure is placed in the rock below the ore body. Since most of the ore bodies are not tall, it is often possible to leave the top column or leave a thickness of 4 to 5 m. Therefore, the total amount of mine bottom pillars accounts for only 3 to 5%. The slope of the electric ramp varies between 0° and 18°, preferably between 5° and 10°, and the maximum is no more than 18°. The funnel spacing is 6m.
When mining, use the YT-25 or YG-30 rock drill to make horizontal blastholes with a hole diameter of 38~40mm and a depth of 3~4m.
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