Application of underground mining in vertical mining of vertical gold stripping

Huayin City of Shaanxi Province Po valley gold ore deposits in accordance with its conditions, the application of vertical striping full cast blasting mining method.

First, mining technical conditions

The Puqi gold deposit belongs to the western section of the Xiaoqinling gold ore belt. The ore body is found in the quartz veins and fractured altered rocks of the gold-bearing structural fracture zone. The thickness of the ore body is 0.20~2.31m, and the average thickness is 1m. The ore body has a dip angle of 9°. The surrounding rock of the ore body roof is altered gneiss or mixed granite , f=10～12, medium stable to stable. The surrounding rock of the bottom plate is stable, and the f=8~10 ore is hard and stable.

Second, mining method structure and mining cutting

The length of the nugget is 40 to 50 m along the strike and 30 to 40 m along the slope. Along the strike, the ore blocks are divided into 5 to 6 mining strips, each of which is 6 to 8 m wide and the length is equal to the length of the ore block.

In the upper and lower levels of the ore block, an in-pulse flat roadway is arranged, the lower horizontal in-pulse roadway is used for transportation and pedestrians, and the upper horizontal in-pulse roadway is used as a return air contact road. The specifications of these roadways are 2m×1.8m, the top plate is the top of the mine bed, and the undercover is excavated to 1.8m degrees.

Before the mining, the trenches are dug in the center of the strip. If the back-type mining is adopted, after the trench is connected with the upper horizontal contact, the trench is used as the cutting space, and the ore is returned to both sides of the mining trench; if the forward mining is used, after a trench is excavated, This is the cutting space for mining, as shown in Figure 1.

Figure 1 Puqi gold mine vertical strip throwing blasting comprehensive mining method

1—transport lane along the vein; 2—recovering the trench; 3—falling the blasthole; 4—mining the blasthole before the trench

5—mine column; 6—return air link; 7—cutting area

Third, mining work

(1) Recovery order and promotion method

The mining is carried out in strips, and the strips are taken as the first branch in the vicinity of the gob. Adjacent strips can be picked up at the same time, but there is a lag in turn. There is a pillar between the first mining strip and the goaf, separated from the goaf. The lean or very thin ore deposit between the parties is reserved as a pillar.

When each strip is harvested, it is divided into forward type and backward type according to the propulsion mode. When the stability of the surrounding rock of the roof is good, the forward type mining is adopted; when the stability of the surrounding rock of the roof is poor, the backward type mining is adopted.

(2) Forward type mining

Firstly, from the inner wall of the tunnel, along the center line of the mining strip, the mining layer with a width of 2.5-3.1 m and a length of 2.0 m is taken, and then the rock below it is produced under the bottom to form a height of 1.8 m, a width of about 2.0 m and a length of about 1.5. m cutting space. According to this process, two cycles are repeated to form a recovery trench having a width of about 2 m and a length of about 4.5 m. The trenching process is shown in Figure 2. After the gully is formed, the ore on both sides is collected into the sulcus by the blasting method and manually loaded and transported. Then carry out mining, mining, and mining, until a complete strip is taken. When mining the ore bodies on both sides of the trench, the angle between the direction of the blasthole and the center line of the trench is 42°~45°, the row spacing of the blasthole is 1m, the blasting is 3~4 rows, the pushing distance is 3~4m, and the blasting effect is 70. %.

Figure 2 Schematic diagram of digging trench

1—intra-pulse transportation lane; 2—recovering trench;

I, II, and III are the first, second, and third mining, trenching

(3) Backward mining

When the stability of the top plate is poor, the back-feeding mode is adopted, and the strip width is reduced to 6 m. When mining, first pick the ore in the center of the strip, the width of the mining is 2.0 ~ 2.5m, and the advancement is 2.5 ~ 3.0m, then the undercover is excavated with a width of 1.8 ~ 2.0m, and the ore on both sides of the trench is not recovered. In this way, the upper ore is excavated, and the lower trench is excavated, and it is propelled step by step until it is connected with the upper horizontal return airway. Then from top to bottom, back to the ore on both sides of the mining trench. The angle between the blasthole and the center line of the trench is 37°~42°, and the throwing blasting is used, and the propulsion is 1.5~2.0m each time. The ore under blasting is transported by hand.

(4) Roof management and powder recovery

In the process of mining, when the local roof is unstable, it is supported by wooden columns. The rock of the trench is collected and the stone collected in the mining is piled up in the goaf outside the blasting area to support the roof. The powder ore produced during the blasting process should be carefully cleaned and shipped in bags.

Fourth, technical and economic indicators

The main technical and economic indicators of mining methods are shown in Table 1.

Table 1 Main technical and economic indicators of mining methods

V. Evaluation

Compared with the original mining method of the mine, the mining method has the following advantages:

(1) The ore loss rate decreased from 20.15% to 13.2%, and the depletion rate dropped from 27.64% to 11.76%. The poverty index has dropped significantly.

(2) The amount of mining work is reduced.

(3) Each branch can be recovered at the same time, and the production capacity of the ore block is increased from 25 to 30 t/d to 30 to 50 t/d.

The main disadvantages of this mining law:

1. The degree of mechanization is low, and the digging and transporting of rock and ore are all manual operations, and the physical labor is heavy.

2. Before the sulcus and the upper horizontal return airway are connected, it is a single operation and the ventilation conditions are poor.

The applicable conditions of this mining method are: gently inclined, thin and extremely thin ore body, the roof is medium and stable, and the boundary between the ore body and the surrounding rock is obvious. When the thickness of the ore body exceeds the height of the mining width, it can be advanced in full section.