Zijin Gold has been mined copper mine near 25a, the mining of copper has been mined 460 and 520m level, open-air gold mine exploitation of resources is expected to be completed by 2018, will be Zijinshan gold and copper open-pit mining, the mining model to a mining joint completely Underground mining mode. The two horizontal goafs of copper mines are as high as 120m, which is a safety hazard for open-air production and an important factor restricting the transformation of mining modes [1]. In order to maintain the economic benefits of the Zijinshan Gold-Copper Mine, it is necessary to treat the goaf of the 460,518m middle section of the copper mine to eliminate potential safety hazards and prepare for the transformation of the mining mode. Where d is the pore size, 85 mm. Where m is the deep hole density factor, which is 1.625. Calculate the bottom hole distance of the blasthole hole a=2.76m. Where q is the explosive consumption, 0.65kg/m3; b is the row spacing, 1.7m; n is the number of rows of blastholes, 7 rows; S1, S2 are the area of ​​the miner funnel, the area of ​​the partition, respectively 207 .5m2. The total dose of the 7-row hole blasting design is calculated to be 1605kg. The safe allowable distance of the blasting shock wave is calculated to be 293m. At the blasting site, the chamber with anchor spray support is selected as the detonation point to ensure the safety of detonation.
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1 stop overview
The lithology of the goaf in the middle part of the Zijinshan gold-copper mine is mainly weakly weathered medium-grained granite . Locally visible cryptoexplosive breccia, Ying'an porphyrite and quartz porphyry are mainly distributed in veins or lenticulars in medium and fine granules. In the granite; the main engineering geological rock group of the copper deposit is complete and rigid, the Rc is not less than 60 MPa, the RQD is not less than 75%, the fracture is less than 2 groups, and the spacing is greater than 1 m. The rock is fresh and complete, and the water is very weak - water-tight, partially weak, and the rock is of good quality. The core is mainly composed of long column-long column, the rock body is relatively complete-complete, and the engineering geological conditions are good. The ore-bearing rocks of the copper ore body of the mining area and the surrounding rocks of the top and bottom plates are mainly medium-fine grain granites, followed by cryptoexplosive breccia and a small amount of Ying'an porphyrite. The ore is stable and the tunnel is generally unnecessary.
Support.
There are 55 mining houses in the middle section of 520m and 36 in the middle section of 460m. The goafs in the middle of the two sections overlap and calculate 36 mines to be blasted. The plane position of the goaf is on the 0 to 15 line, and the vertical direction is on the level of 460 to 570 m. The mine is 15m wide, and the mine compartment is about 15m wide and has a length of up to 120m. The shape of the mined area of ​​the mine is relatively regular, which is similar to the rectangular parallelepiped. The average thickness of the 510-520m horizontal pillar is 8.3m.
2 goaf treatment method
According to the mine research, it is decided to use the caving method to treat the goaf, that is, to first collapse the 520m horizontal pillar, penetrate the 460,520m level, and then collapse the 30m thick isolation pillar in the open pit, transport the low grade ore in the open pit, and directly fill it. Gob area to reduce safety hazards in the goaf and control mine pressure. Therefore, blast caving must be carried out on the 520m horizontal pillar [2-4].
3 collapse method blasting design
3.1 Test stop selection
A total of 36 stope in the middle section of 520m need to be blasted. According to the physical and mechanical properties of the typical ore in the Maanshan Mine Research Institute and the evaluation results of the surrounding rock stability of the goaf, the 1-3 stope is located on the 7th to 11th lines. Surrounding the field strength is highest stope 520m middle, and belong to the basic region solid (â…² level), suicide, alunite alteration of strong, hard rock, partially opened by the petrochemical, and sericite of a semi-rigid state, The joint fissures are relatively developed, the roadway is wet, and occasionally seepage or dripping, mainly characterized by the integrity of the semi-rigid engineering geological rock group, and the surrounding rock of the roadway and its roof is basically stable. Choose the hardest and most stable 1-3 stop for blasting tests.
3.2 perforation design
Drilling boring machines are arranged on the roadway on both sides of the stope, and the fan-shaped medium-deep holes are arranged in the vertical roadway direction, and the blasting caving 510-530m horizontal pillars. The horizontal pillars of each mine are arranged with 7 rows of fan-shaped holes (Fig. 1): one is a grooved row, the third, fourth and fifth rows are single-sided holes; the other is a positive row, the first one The second, sixth, and seventh rows are bilateral holes. The trough row blasting forms a trough space, and is discharged to the adjacent goaf to blast the ore. 
3.3 blasting parameter design
3.3.1 positive row
3.3.1.1 blasthole diameter
This design uses T-100 high-pressure annular down-the-hole drilling rig , 85mm ball-toothed drill bit, the diameter of the positive row blasthole is 85mm.
3.3.1.2 Minimum resistance line
Calculated according to the hard rock formula:
Calculated W = 1.7 ~ 2.55m, take 1.7m.
3.3.1.3 hole bottom distance
According to the calculation formula
3.3.2 slotted row
According to the blasting parameters of the row and the particularity of the groove row, the blasting parameters are selected: the diameter of the blasthole is 85mm, the minimum resistance line is 1.6m, and the hole bottom distance is 1.6~2m.
3.3.3 Explosives consumption
According to the experience of other metal mine empty area treatment, the explosive unit consumes 1.3 times of the normal consumption of the normal step deep hole blasting explosive in the same part. Therefore, the explosive consumption of the 520m horizontal pillar of this blasting process is 0.65kg/ M3.
3.3.4 Calculation of dose
Calculate the total amount of blasting Q by the unit consumption of explosives, average to the amount of blasthole per row, and finally distribute the dose of each blasthole evenly according to the length of the blasthole.
3.3.5 Charge structure
The 60mm2# rock emulsion explosive is used, and the charge is coupled. In the middle of the blasthole, a roll of detonation kit with a non-conducting squib detonator is installed. The medium-deep hole is used as a primer, and the deep hole is made into two detonating kits. The length of the plug is 2.5 m. The structure of the medium and deep hole charge is shown in Figure 2.
3.3.6 detonating network
The non-electrical millimeter detonators that are led out in the same row are connected by a bundle of two non-electrical millisecond detonators, and the outer holes are connected to the main detonation network. The network connection is shown in Figure 3. The blasting parameters of the 1-3 stope hole are shown in Table 1.
3.4 Minimum safe distance calculation
There is a pillar blocking in the goaf, which can be neglected by the influence of individual blasting flying stones. According to the safe allowable distance empirical formula of blasting shock wave
Considering comprehensively, it is determined that the blasting warning distance is 350m.
3.5 Safety technical measures
(1) Since the middle section of 520m is located directly below the open pit, the open-pit blasting vibration will cause deformation and destruction of the surrounding rock of the roadway, and the blasting vibration of the partition will also affect the damage of the surrounding rock. Therefore, before rock drilling and charging operations Make a knock on top to ensure the safety of the work surface [5].
(2) Slotting the position of the blasthole strictly according to the design requirements. The rock drilling rig must drill according to the design angle and depth, do a good job in detecting and registering the blasthole quality, make up the abnormal hole, and form the inspection hole after all the holes are formed. In summary, provide a basis for per-pore volume design.
(3) The fracture of the rock layer makes the blasthole easy to seep. Before the charge, the high-pressure pump must be used for water blowing operation. The charge is smooth and the medicine package is connected to ensure that the bombardment wave is transmitted to each drug pack, and the explosion is started smoothly to prevent the explosion.
4 Conclusion
According to the blasting plan, the construction was successfully carried out, and the blasting was successfully carried out. The actual blasting used was 1,580 kg of explosives, the unit consumption was about 0.64 kg/m3, the detonator was 210, and the detonating tube was 1000 m. The horizontal pillar separator and the tapping funnel all collapsed to the middle of 460m. There is no super-explosion, which protects the integrity of the mine and obtains good blasting effect. The subsequent mining blasting construction can be used as a reference. According to the actual situation of the surrounding rock of the stope , properly adjust the blasting parameters, safe blasting.
references
[1] Shen Qihong. Control factors for comprehensive treatment of goaf in complex layer group of Zijinshan gold-copper mine [J]. Modern Mining, 2016 (6): 228-230, 232.
[2] Zhang Chengliang, Hou Kepeng, Li Kegang. Application practice of chamber blasting method in treating goaf [J]. Engineering Blasting, 2008 (4): 53-56, 59.
[3] Li Junping, Xiao Xufeng, Feng Changgen. Research progress in goaf treatment methods [J]. Chinese Journal of Safety Science, 2012 (3): 48-54.
[4] Liu Jiandong, Chen Yi, Sun Zhongming. Practice of blasting and caving of the lower landslide body in the extra-mining area [J]. Engineering Blasting, 2012(2): 33-35, 59.
[5] Zhu Dayong, Qian Qihu, Zhou Zaosheng, et al. Critical slip field of slope based on residual thrust method [J]. Journal of Rock Mechanics and Engineering, 1999(6): 667-670.
Article source: "Modern Mining", 2016.12
Author: Wang Shi-hyun; Fujian Straits Branch of the Fu Hing Construction Co., Ltd.
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