Research and Application of Controlled Blasting and Mining Method in Jinchangyu Gold Mine (Underground Mining of Rock Gold Deposit)

The Jinchangyu Gold Mine uses the retention method as the main mining method, and its mining volume accounts for 56% of the total mining volume of the whole mine.

First, mining technical conditions

The Jinchangyu gold deposit is a medium-temperature hydrothermal fissure filling type. There are 6 vein belts in the mining area. The length of the ore body is generally 50-150 m, and the longest is 300 m. The mineralized belt has a total length of 1500 m and a strike of 30°. The ore body has a dip angle of 60° or more and tends to the southeast. The ore body is vein-like and lenticular, with an ore body thickness of 1 to 6 m and a maximum thickness of 24 to 40 m. The stability of the ore stabilized ore is ƒ=7～8, and the rock ƒ=8～12. Minerals pyrite-based, semi-euhedral shape and grain structure, with irregular shaped gold natural pyrite particles filled in, in the mineralization ring against gold grade ore, ore boundary Grade 1.5g/t. The ore is non-oxidizing, pyrophoric and cohesive, and has poor water content.

Second, the application of controlled blasting technology back to the mining room

(1) Ordinary upward blast hole mining back to the mining room

In the past, the Jinchangyu gold mine has been used to control the blasting to the ore hole. The hole spacing and row spacing are generally 0.8-1.1m, the hole depth is 1.5-2.0m, the hole diameter is 38-42mm, and the mine length is 30-32m. The thickness of the ore body is 28 to 29 m high. The half or full length of the blasthole of the mine has finished the blasthole, and multiple rows of the same section of differential blasting are used. After the blasting, the roof of the mine is seriously damaged, forming a blasting relaxation zone of 0.5-0.7 m, which causes the following problems:

1. Workers always carry out all mining operations under the damaged roof, and safety production is seriously threatened;

2. The workload of inspection and dome is large, labor intensity is high, and safety is poor;

3, due to the use of equal hole spacing and row spacing, the cutting type of blasting, easy to produce large blocks, the secondary crushing volume of the stope is large, while the flat field workload is large and heavy, generally takes 3 ~ 6d;

4. For the next cycle, the mining operation is safe, and the support is also required after the flat field. In general, a wooden main column is required for every 6-10 m ^{2 of the} stope. For example, there are many cracks in the ore body. In the process of flat field, the raft should be supported.

Ordinary upward blasting technology, due to the large working area, it is possible to use multiple machines to simultaneously drill rock, which is convenient for centralized operation to improve labor productivity. Therefore, the ore-mining process is suitable for the stability of the ore body and surrounding rock, the thickness of the ore body is less than 6m, and the steep slope shape of the exposed roof area of ​​the stope is less than 300m ² compared with the regular ore body occurrence condition.

(2) Horizontal blasthole control blasting falling mine back to mining room

In view of the problems existing in the normal upward blasthole mining, the mine and the Maanshan Mine Research Institute collaborated to study the horizontal blasthole control blasting technology.

This horizontal blasthole mining process uses the smooth blasting technology as the basis for the peripheral hole blasting of the mining, so that the blasthole density coefficient increases from 0.8 to 1.0 to 1.3 to 1.4, and the other blastholes use small resistance lines and large hole spacing. The hole density factor is 3. All the holes are curved on the working surface and the plume is arranged between the holes (Fig. 1).

Figure 1 Schematic diagram of horizontal blasthole control blasting arrangement

In order to achieve water blasting, it is first necessary to excavate the cutting groove at both ends of the stope as a horizontally propelled blasting free surface. The height of the cutting groove is equal to the height of the mining layer, which is 2.5 m, and the length along the strike is 2.5 to 3.0 m, and the width is equal to the thickness of the ore body.

The surrounding horizontal hole spacing is 0.8-0.9m, the minimum resistance line is 0.6-0.7m, the hole depth is 2.0-2.5m, the blasthole charge concentration (ammonic fry) 0.3kg/m, air-spaced charge (Figure 2).

Figure 2 Schematic diagram of the surrounding hole charge structure

1—gun hole; 2—air interval; 3—millisecond detonator; 4—plastic detonator tube; 5-ф32mm drug roll

The hole spacing of other blastholes is 1.5-1.8 m, the minimum resistance line is 0.6-0.7 m, the hole depth is 2.0-2.5 m, the blasthole charge coefficient is 80%, and the charge structure is column-shaped reverse continuous charge.

The non-electric millisecond detonator is used to detonate, the same row is in the same row, and the row is slightly blasted.

Horizontal blasthole control blasting test results show that the roof is flat, the residual rate of the semi-hole after blasting is greater than 50%; there are few pumice stones , basically no bristles; the roof is stable, basically no wooden support; The rate is small (less than 5%), the amount of secondary crushing is small, and the amount of work in the flat field is small, which shortens the preparation time of the lower cycle.

(3) Alternately controlling the blasting and falling back to the mining room

Although the horizontal blasthole control blasting test has achieved good results, it is difficult to greatly improve the labor productivity because the horizontal blasthole mining is limited by the working surface. Therefore, after the horizontal blasthole control blasting, the ordinary upward blasting hole is performed. Mine, to achieve a combination of horizontal and vertical integration method. In this way, the mining operation is always carried out under the roof of the horizontal blasthole control blasting, the stability of the roof is good, and the operation is safe and secure. However, due to the general upward blasting of the blasthole and the high bulk yield, the secondary broken explosive is consumed more.

In order to obtain better technical and economic effects, the experimental research on the upward blasting control blasting was completed, and the perfect mining technology combining horizontal blasthole controlled blasting and upward blasthole controlled blasting was realized.

The upward blasting of the blasthole is also required to dig the cutting groove. Generally, the cutting groove is opened by the wedge-shaped grooving method or the existing surface of the mining room is used as the free surface of the upward blasting.

Uphole hole blasting is based on the principle of large hole spacing, that is, the hole spacing is 1.5~1.8m, the row spacing (minimum resistance line) is 0.6~0.8m, the blasthole density coefficient is 2.5, the hole depth is 2.0m, and the charging coefficient is 80%. (Ammonic Fry), the charge structure is a reverse continuous charge.

The hole is filled with mortar and mortar 0.2m. The non-electric millisecond detonator is used for two blasting, and the slot hole is first exploded, and then the mine hole is exploded. 2 to 3 rows of holes in the same section, partition clusters connected lines, double detonation network, fire detonators detonated.

The uphole control blasting reduces the bulk rate to less than 6.8%.

(IV) Comparison of the effects of the four types of mining methods

The Jinchangyu Gold Mine retaining mining method mining house has carried out a series of experimental research on the mining technology, and the technical and economic effects obtained are very significant, which makes the control blasting technology fall day by day.

The effects of the four mining methods applied in the mine are listed in Table 1.

Table 1 Technical and economic effects of four types of mining methods

It can be seen from Table 1 that the horizontal and vertical holes alternately control the mode of blasting, and the technical and economic effects are most prominent. For similar mining conditions, the mining method should be promoted.

Third, mining pillar mining and goaf treatment

(1) Top and bottom column mining

The mine retention method uses a funnel electric ramp bottom structure. In order to reduce the amount of bottom pillars, the electric ramps are generally placed at the stage transportation level and loaded with the skimming station. The funnel spacing is 5 to 7 m, the bottom column is 6 to 7 m high, and the top column is 5 m thick.

In the upper stage, the bottom column and the top column are simultaneously recovered. In the upper stage, the YZG-90 type rail rock drill is used to cut the fan-shaped medium-deep hole to the top column, and the upper-stage bottom column is chiseled to the fan-shaped middle deep hole, and the cutting well is drilled in the center or both ends of the top column. The row spacing of the blasthole is 1.3 to 1.5 m, the distance between the bottom of the hole is 1.5 to 1.8 m, and the depth of the hole is 3 to 7 m. The top column hole is blasted by multiple rows of the same section, and the bottom column hole is blasted by the same section ("one slam") (Fig. 3).

Figure 3 Deep hole arrangement in the top and bottom columns

Years of production practice has proved that the top and bottom columns of the mining and mining method by the above method have a good effect, which not only ensures the quality of the blasting, but also reduces the consumption of explosives and reduces the mining cost.

(2) Inter-column mining

The width of the column is 8-10 m, and the length of the column is equal to the thickness of the ore body. In the inter-column contact road, a fan-shaped medium-deep hole is chiseled, and generally 5 to 7 rows of holes are arranged along the strike line, and the upper layered blast hole rows are required to correspond to each other. The detonators of the same section of the blasthole are detonated with good results (Fig. 4).

Figure 4 Arrangement of the blast hole in the mining

(3) Gob area treatment

The goaf of the Jinchangyu Gold Mine is north of the No. 11 exploration line and is close to the surface. With the natural collapse of the goaf, it will reach the surface and reach the purpose of treatment. In the goaf area south of the No. 11 exploration line, due to the deeper surface, the method of excavating the “sunroof” from the goaf to the surface is adopted to reduce the harmful effects of the impact of the large amount of rock in the goaf.