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An example of an empty area for the collapse of surrounding rock
   A copper mine guanshan breakout force Surrounding processing Gob
The Tongguanshan copper deposit is a hydrothermal contact metamorphic metamorphic skarn type copper- sulfur deposit. The ore body is like a layered output, the upper part is relatively large, and the deep part is gradually narrowed and branched, and the thickness of the ore is 2 to 33 m. The inclination angle is 32 to 82°. The upper plate is quartz diorite , which is very stable. The lower plate is quartz shale , which is stable to moderate stability, but it is soft and brittle and has poor stability due to the influence of the fault at the contact of the rock. The ore is stable and the copper grade is 0.71%. The surrounding rock contains very little copper. Pyrrhotite, pyrite ores easily oxidized under certain conditions, spontaneous combustion and agglomeration. Some mining sections of the mining area are mined by the stage mining method and the retention method. By 1982, the goaf had a volume of 4,942,500 m3 . It is difficult for the surrounding rock to stabilize and collapse naturally. The empty space is treated by arranging the medicine chamber on the upper part of the ore body and partially assisting the deepening of the surrounding rock by deep hole blasting. It is required to form a mat thickness of not less than 20 m. Table 1 shows the treatment status of the mines in the mines in 1980. The schematic diagram of the treatment area of ​​the chamber collapsed surrounding rock is shown in Figure 1.
Table 1 Treatment status of each section of Tongguan Mountain
Mine section
Going long
(m)
inclination
(°)
Elevated stage elevation
(m)
Total empty area
(million meters 3 )
Empty area
Pine tree mountain
260
23~45
Average 30
35, 5, -25, -55, -95
85.8
There is filling in the empty area, and the amount of surrounding rock is about 370,000 m3 , and some surface subsidence
Old temple base mountain
190
30~55
Average 38
35, 5, -25, -55, -95, -135
166.6
The empty area is filled with fillers, and the amount of forced rock is about 890,000 m3 , forming a loose cushion with a thickness of 30 m.
Little Tongguanshan
180
43～60
Average 55
95, 65, 35, 25, -55, -95, -135
107.9
The pharmacy collapsed on the roof and the surface has fallen.
Lushan
200
33～78
Average 58
17
6.2
Underground mining to surface open pits, surface subsidence filling empty areas
Baoshan
200
55～67
Average 57
95, 55, 11, -30, -80, -130, -170
54.3
Multiple use of the drug chamber collapsed the roof, the surface collapsed and filled the empty area
Fig.1 The blasting and caving surrounding rock treatment area of ​​Tongguanshan Copper Mine
1- gob area; 2-pharmaceutical room; 3-contact roadway; 4-deep hole rock drilling chamber; 5-resist line; 6-designed collapse surrounding rock boundary
Practice has shown that the timely treatment of the mined area of ​​the mine has a significant effect on ensuring the safe production of the lower part. For example, the old temple base mountain section has been recovered to -175m level, the depth of mining is more than 200m, and the exposed area of ​​the roof of the empty area is large. However, due to the thick rock layer of more than 20m in the upper part of the operation stage, several large times have occurred in the past years. The roof surrounding rock collapsed, but it did not affect safety production.
   Second, the Tieshan Ridge tungsten mine collapsed wall treatment empty area
Iron Mountain Mine sand ridge tungsten ore vein with 16 lines hydrothermal quartz vein wolframite deposits, occurs in quartz sandstone slate, veins or steeply inclined surface directly exposed population. The ore is medium in stability and the mining area is steep.
The single vein of the upper part of the vein has been used in four stages. The lower veins are densely converged, the pulse width is increased, the pulse distance is reduced, and the bandwidth is 9-16 m. The stage mining method is arranged along the strike. After the upper single-pulse mining, the empty area is larger. Although some empty areas are filled with waste rock, it is difficult to control the movement of surrounding rock and wall due to low filling rate (52%). In order to create better safety conditions for the lower mining, the wall between the top and bottom columns of the ore and the empty area mined by the upper stage mining method is forced to collapse with deep holes (Fig. 2).
Figure 2 Tieshan Ridge Tungsten Mine
1-gun hole; 2-clamped wall; 3- partially filled empty area
The deep holes of the collapsed wall adopt four types: horizontal fan shape, vertical fan shape, horizontal parallel, and vertical parallel. Rock drilling with the YQ-100 drilling rig and concentrated blasting. The hole diameter is 100~110mm, and the hole depth is 10~20m.
The surface topography of the vein belt is high in the east and low in the west, and the grade gradually decreases from west to east, and the thickness of the empty section increases gradually. Therefore, the requirements for each section are different: all the west collapses to the surface; the middle part collapses in two stages; in the east, only 20m thick rock cushion is required. The first two parts of the fallen rock are recovered because they contain a certain amount of tungsten. The technical and economic indicators for the forced collapse wall treatment empty area are as follows:
Number
Wall with pulse rate (%) 11
Comprehensive grade (%) 0.137
Ore avalanche (ten thousand tons) 13.85
The amount of metal recovered (t) 189.9
Long processing range (m) 140
Wide processing range (m) 11
Total depth of blasthole (m) 7394
Explosive total consumption (t) 14.2
Unit explosive consumption (kg/t) 0.26
Rock mass per metre of blast hole (t/m) 18.7
Unit empty area processing fee (yuan/ m3 ) 1.77
Total cost of empty area treatment (ten thousand yuan) 22.57