Static shrinkage stoping method experimental study carried out in Dongtongyu gold mine. The experimental research has achieved good technical and economic effects, which indicates that it is feasible to adopt static mining and mining method for unstable surrounding rock.
I. Problems in the geology of deposits and the application of ordinary retention methods
The No. 1 vein of Dongtongyu Gold Mine is a steeply inclined thin ore body with an inclination of 70-80Â°, an average thickness of 2.62m, a partial thickness of 5-7m, and an average grade of 7.41g/t. The ore body is located in the modern mineral tectonic belt. The average thickness of the tectonic belt is 8.63m. It is composed of various extruded schist, physicochemical diabase and fragmented rock. There is fault contact between the ore body and the surrounding rock, and the fault plane is mostly filled with fault mud, and is squeezed by the later structure, with small displacement. The surrounding rock joints develop and form a fracture zone. Therefore, the surrounding rock of the upper and lower plates are not stable. Between the gold-bearing quartz veins have small veins interspersed, it is a medium firm.
Since the mine was put into production, it has been mining by ordinary mining method. In the process of mining, a large number of surrounding rocks are placed on the upper and lower plates, so that the ore grade is reduced to 2.5~1.56g/t, and the ore depletion rate is as high as 57%-75%. The surrounding rock often blocks the concentrating funnel, consumes a large amount of wood and explosives, so that the collected ore can not be released, resulting in a large loss of resources, the ore loss rate of 32%, seriously affecting the economic benefits of mine production and enterprises.
In response to the above problems, Dongtongyu Gold Mine cooperated with Xi'an Metallurgical and Architectural College and Shaanxi Gold Company. From March 1991 to May 1993, it carried out mining technology water attack and experimental research, using static mineral filling and cement roller anchors. Comprehensive technical techniques such as supporting surrounding rock, horizontal blasthole control blasting and falling, and the bottom structure of the lower-plate flat-bottom electric raft have achieved good technical and economic effects.
Second, the main results of scientific research
(1) Technical conditions and structural parameters of mining stope mining
The test was selected at the No. 501 and No. 502 West Wings of the 679 phase II ore body of the Q 1 vein. The ore body has a dip angle of 79Â° and a thickness of 1.9 m. The ore firmness coefficient is 10=10~12, and the joint fissures are developed and interspersed with veins. The surrounding rock of the ore body is a structural fracture zone, which is very unstable and is difficult to mine.
The exit section is 35m high, the 501 stope is 50-60m long, and the 502 stope is 30m long. Without leaving the top column, the bottom column is 6m high, the column width is 3~4m, and the spacing of the ore discharge is 5m. Patio and electric ramps, stage transport lanes are arranged outside the lower disc. The flat bottom electric ramp bottom structure is used (see Figure 1).
Figure 1 Static mining method of No. 501 stope
1â€”transportation laneway; 2â€”passage roadway; 3â€”raceway patio; 4â€”through-pulse communication road; 5â€”pathway along the vein;
6â€”Electric Ramp; 7â€”Cut Road; 8â€”Local Mine Leaching; 9â€”Single Bucket Partial Release; 10â€”Cement Roll Anchor
(2) Horizontal blasthole controlled blasting
Due to the development of ore joints and the intertwining of veins, it is safe for the mining work, and the upper blastholes used in the past are changed to horizontal blasthole controlled blasting. The horizontal hole spacing is 0.6m, the edge hole is 0.7m away from the surrounding rock contact surface, the row spacing is 0.6m, the hole depth is 1.8m, and the rows of blastholes are arched (see Figure 2).
Figure 2 Charge structure
The air column spacer charging structure is adopted, and the air column of the middle blasthole of the ore body is located at the bottom of the hole (see Fig. 3a), the charging coefficient is 0.75-0.8; the edge of the ore body is blasted, and the air column is in the middle (see Fig. 3b), the charging coefficient 0.5 to control the charge of the blasthole at different positions.
Figure 3 Charge structure
a-II beat drug structure; b-I, II row charge structure
1â€”blasthole; 2â€”drug roll; 3â€”priming roll; 4â€”cavity
The non-conducting squib is slightly detonated, the same row and the same segment, multi-row segmentation (segment difference is not more than 50ms), one detonation.
The practice of controlled blasting proves that the ore is broken evenly, the bulk rate is reduced, the destructive impact on the surrounding rock is alleviated, and the stability of surrounding rock is played well.
(3) Cement roll anchor support upper and lower plate surrounding rock
According to the on-site observation, when returning to the mining room, the surrounding rock began to fall for 15-20 hours. In order to control the surrounding rock fragments in time, the upper and lower disc rocks are supported by cement coil anchors.
Two kinds of cement rolls with outer diameter Ñ„38mm, inner diameter Ñ„8mm and length 250mm are made of expanded cement. The anchor rod is made of Ñ„4ï½ž16mm round steel. The anchor length is 1.8ï½ž2.0m, the bottom end has Ñ„36mm, 3mm thick washer, outer end. There are 10cm threads. Before the anchor hole is not installed, the cement roll is immersed in water for 3~5s and then quickly loaded into the anchor hole. The cement roll is compacted with the impact tube. After 5 minutes, the plate is clamped on the anchor and the nut is tightened. After 24 hours, Tighten once.
The bolt net is 1.2mÃ—1.2m, and the surrounding rock of the upper and lower plates is fully anchored. The average pull-out force of each anchor was 39.76 kN as determined by the pull test. After the mine was exposed to the mine, the anchor rod had a good effect on the surrounding rock support. The cost of the bolt is 1.88 yuan / t.
(4) Static mineral filling and filling mine
In the process of mining, the frequent local ore deposit method creates conditions for the deformation and failure of the surrounding rock. The production practice proves that the dynamic retention of the ore in the stope does not support the surrounding rock, and the ore of the local ore is moved downwards to the full impact of the frictional impact, which in turn aggravates the surrounding rock fragmentation.
The static retention process is to take two-thirds of the ore remaining in the stope, similar to the filling and filling of the stope. During the period of returning to the mining house, it remains statically in the stope, supporting the surrounding rock and the surrounding rock. One-third of the local mined volume is discharged from the stope into a dedicated chute. In this way, the mining process of the retention method is used, and the deposit ore has the characteristics of a dry filling mine, which effectively maintains the unstable surrounding rock of the upper and lower plates.
(5) Technical and economic effects
The comprehensive techniques such as horizontal controlled blasting, cement-rolled anchor-reinforced surrounding rock and static-retained ore-filled mining house have played a good role in maintaining the stability of surrounding rock, and the static ore-filling ore is a mining method. The new technology has enabled the mining method to be successfully applied to medium-thick ore bodies where the steep slope surrounding rock is unstable, which expands the scope of use of this mining method. The research results have common social benefits.
The main technical and economic indicators obtained from the test stop are listed in Table 1.
Table 1 Main technical and economic indicators of static retention method
Ordinary retention method
Static retention method
Excavation grade /gÂ·t - 1
Mining Class Efficiency / tÂ·Taiban - 1
Stope mining capacity /tÂ·d - 1
Mining ratio /mÂ·kt - 1
Ore depletion rate /%
Ore loss rate /%
Bolt support fee / yuan Â· t - 1
It can be seen from Table 1 that except for the mining ratio of the test stop, which is larger than the ordinary retention method, other indicators are better than the ordinary retention method, the ore grade increased by 118.4%, and the mining capacity increased by 77.8%. The ore depletion rate has decreased from 66.0% to 17.55%, and the ore loss rate has decreased from 32.0% to 11.48%.
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