Application of open pit mining-open-air joint mining plan in Yanjin Mine

Long high gold mine in Tianlin County, Guangxi Zhuang Autonomous Region, is a fine grained disseminated gold deposits, metallogenic condition better mines, which uses open a joint underground mining technology.

I. Mining body mining technology

There are 9 ore bodies in the Jigongyan section of the Gaolong Gold Mine, of which the No. 6 ore body is the largest (its reserves account for 96% of the entire section), 800 meters long, 285m in depth, and 1265~ At 1180m, the ore body is vein-like and lenticular, and the branching and compounding phenomenon is common. There are not many branches in the 1220m elevation, the shape is regular, and the ore body is thick. In between 1220 ~ 1130m elevation, bifurcations prominent, reducing the thickness, especially in the 1190 level, the largest stock in ~ 1140m, the mineral stone 20.6t, only 41 000 t in the high average 10m segment, but also the lowest grade . The composite thickness of the ore body below 1130m elevation becomes larger, the average thickness of the ore body is 23.69m, the inclination angle is 50°~60°, and the average grade of ore body is 3.71g/t.

Second, the choice of mining plan

According to the occurrence conditions of the ore body, if the whole open-pit mining method is adopted, the production will be reduced in the middle-poor section, resulting in discontinuous production, and the stripping flood peak just happens during the transition period of the lean-poor area, and secondary investment must be made, which will seriously affect Enterprise economic benefits. Through multi-program technical and economic comparison, it is determined that the open-ground combined mining is the best solution, the intermediate grade is abandoned and the stripping peak is avoided. The scheme comparison is shown in Table 1.

Table 1 Technical and economic comparison of mining schemes

It can be seen from Table 1 that in the aspects of annual profit, investment profit rate and seeding after returning to the book, the II scheme is higher than other schemes, and the return period is the shortest, and the initial mining grade is high, which is conducive to returning to the original. Joint mining is reasonable.

The Gaolong gold mine is divided into east and west by 22 lines. The western ore body is distributed in the middle of the 4-16 line, the top is thick, and at the 1190m elevation, the ore body becomes thinner and the selected ore is sharply reduced. The ore body is distributed between 22 and 50 lines, the top is thick, to the elevation of 1180m, the ore body is thinned, and the amount of minerals selected is sharply reduced, but several of them still have more heap leaching. The exposed area is the thick part of the top of the ore body (see Figure 1).

Figure 1 The plan of the combined step mining infrastructure

The underground mining area is the deep ore body outside the western open-air boundary of No. 6 ore body, specifically the ore body between the 6th and 22nd lines of 1160～1015m. The reserve utilization reserves are shown in Table 2.

Table 2 Circled Reserves

Third, open pit mining

The upper part is mined in two small open pits in the east and west. The average stripping ratio is 1.83t/t, and the selected ore is 3.18t/t. The boundary parameters are shown in Table 3.

Table 3 boundary parameters

As the surface of the ore body is exposed at an elevation of 1265 to 1180 m, the inclination is consistent with the slope direction of the slope, and the inclination angle is 50° to 60°. Therefore, the slow working is used to help the longitudinal stripping process, and the single wall roadway along the hillside terrain is drilled to the upper part of the ore body. Then push from the upper plate to the lower plate. Car transportation is used to meet the needs of complex ore mining and rich and poor mining. When the upper and lower V-belts of the ore body are recovered, the ore is divided into sub-explosives.

The KQD-80 type down-the-hole drilling rig was selected as the perforating equipment. The ore was blasted with medium-deep holes. The No. 2 open-air rock explosive was selected, and the non-electrical detonation system was detonated.

The ZL-50 front-loading machine is used for mining, and the QUD-20 excavator is stripped.

The height of the mining steps is 5m. For mining gold ore bodies such as Gaolong, which have complex shapes, large thickness changes, difficult inclination control, and large grade changes, low-step mining is an effective means to reduce loss and reduce recovery.

The shovel face parameters are as follows

Fourth, underground mining

According to the occurrence conditions of ore bodies and the requirements of underground mining during joint mining, the underground mining adopts the segmented and divided gravel cementation filling method, and the individual rock mass has better stability and adopts the upward stratified filling method.

In order to ensure the production of the third-grade ore and the normal production, the intermediate mining block is used to push down, and then the upper mining block is taken in the order of mining, that is, the first 1090m middle section is adopted, then the 1050m, 1015m middle section is adopted, and the last mining is 1130m. Middle section.

The Pingyi slipping well development plan was adopted. The elevation of the middle section is 1160m, 1130m, 1090m, 1050m, 1015m, of which the middle section of 1050m is the main transport plane, which is responsible for the transportation of ore from the underground; 1090m is the middle section of the first mining, and the middle section of 1130m is the middle section of materials, personnel, equipment, Fengshui and other transportation, 1160m To fill the middle section. The various sections can be connected by ramps, pipe wells and pits. The ore below the middle of 1015m is developed by blind inclined shaft. The composition of the ore block is shown in Table 4.

Table 4 Elements of the nuggets

When the horizontal thickness of the ore body is greater than 20m, the vertical ore body of the mining strip is placed face to face; when less than 20m, the strip is arranged along the direction of the ore body.

When mining the mining, in the section mining roadway, the YGZ-90 type rail rock drill is used together with the TJ25 type rig to drill the upper parallel deep hole or the upper fan shape medium deep hole. The diameter of the blasthole is 65mm, the hole spacing is 1.5m, and the minimum resistance line is 1.5m. After all the medium and deep holes in the strip are drilled, the rock drill is withdrawn and the end of the strip is retracted. The charge is made of BQF-100 type charger, and the explosive is No. 2 rock ammonium nitrate explosive. It is detonated by non-conducting blast pipe, and 2 blasts are exploded at a time, and the step of collapse is 3m. After the blasting, the fan is pressed into the ventilation, and the sewage is filled into the upper and middle sections of the returning windway through the segmented filling roadway and the ventilation patio of the stope. The ore is transported to the mining site by the EHST-1A electric shovel. The ore is scraped and cleaned and filled.

The filling adopts the combination of electric shovel and self-flow, and the artificial slab wall is built in the section mining roadway before each filling to prevent the loss of the filling.

The mining strips are divided into 4m wide and 8m high. For the irregular ore body mining and striping, the width, length and arrangement form are determined according to the stability of the ore rock.

In the middle section, the bottom section is sequentially harvested, and the first section of ore is placed in the lower middle section by the chute to reduce the loss of the ore.

Before the first section is completed, the tunnel is built through the vein and the slipway is formed to form a concrete bottom structure.

The ore collected in various sections is transported to the middle section of 1050m by the mine. The 1050m main transport flat is exported to the northwest of the open pit. The underground mining ore is transported into the mine silo by the main transport, and then transported by the mine to the selected plant.

V. Evaluation

As the depth of the stope continues to increase, the amount of open-pit mining and stripping increases. The use of open-air joint mining can reduce a large number of rock-peeling and reduce mining costs. At the same time, it can improve the quality of the ore and improve the quality of the ore due to the reduction of external drainage. However, there are two sets of production systems in the joint mining, the management is more complicated, and the one-time investment is larger.