Experimental study on mining method of rock gold mine

Zhangjiakou gold mine since 1976, wall caving method according to the original design of the test in the northern two nuggets, not get good results, later renamed route monolayer caving mining. When the method is used to excavate the road, it leaves a regular discontinuous pillar. When the tunnel is excavated, it adopts a receding recovery part of the pillar, and uses the pillar to control the roof at the mining work site instead of artificially releasing the roof. The transition to the comprehensive law.

July 1980 to January 1983, Northeast University of Technology in collaboration with the mine, according to production practice since the mine into production, the stability, fault joint distribution relationship Mined state stope roof and slate roof layer structure is proposed According to the stability of the roof of the whole mine, the corresponding roof consolidation technology and the determination of the mining method parameters are adopted. According to the thickness of the ore body, the single-layer or layered mining method of the pillar mining method is tested separately.

First, mining technical conditions

Changgiakou hydrothermal gold deposit fissure filling type monopulse type gold-bearing quartz veins and altered rock deposit, mineralization within the fractured zone and the press belt, near the main host rock is gneiss and amphibolite plagioclase granulitite rock, and subject to different degrees of sericite, and silicide carbonate effect. At the discontinuity of quartz veins, there are often altered rock deposits. Quartz veins are up to 8.15m thick, the thinnest is only 0.28m, and the average thickness is 2.27m.

The shape of the ore body is very complicated, the thickness and inclination angle vary greatly, and the ore grade distribution is extremely uneven, showing a lenticular shape. The length of the strike and the tendency is up to 800m (interrupted ore body), and the ore body is about 450m long and the shortest is only a few meters. The ore body has an inclination of 14 to 20 degrees and an average of 17 degrees.

After mineralization in the mining area, it is subject to multi-stage tectonic movement, and the fault is very developed. There is a fault every 5 to 7 m along the ore body. Joints and cracks are also very developed. The ore body and the near-rock surrounding rock are fragmented structures.

Second, the mining method test program

The key technology for adopting the room-pillar mining method is to do a good job in roof management. When the thickness of the ore body is less than 2.5-3.0 m, a single-layer recovery scheme is adopted. According to the stability of the roof, the corresponding roof management method is adopted: the roof structure destroys the less stable and stable thin ore body, mainly depends on the pillar supporting the roof and the mine can be unsupported or partially anchored; the roof has a small number of structures. For moderately stable thin ore bodies with good integrity and damage, the mines can be supported by bolts or bolt trusses; the broken and unstable roof with more structural damage or the extremely unstable roof with structural damage should be advanced. Support or anchor and metal mesh joint support.

For medium-thick ore bodies (thickness greater than 2.5-3.0m), before returning to the mining room, cut the roof and use the bolts or anchors to add metal mesh to support the roof, and then descend to the ladder-type back to the mining room.

The long axis of the mine is arranged along the ore body, and the mountain is excavated and cut in the center of the mine, which is connected with the upper stage. Reverse tilt back to the mining room and return to the discontinuous part of the mining column. At the same time, the mine house is anchored. After the mine is harvested, part of the pillars are recovered from top to bottom according to the stability conditions of the roof. The ore is collected and transported to the transportation lane for loading. Workers always work under the roof of pillars and supporting mines, and work safely.

The mining houses are harvested in a certain order, and the mining houses at the end of the mining are closed. After a certain period of time, the roof is naturally collapsed and the gobs are treated by themselves.

Third, thin ore body room column mining method test

(1) Geological conditions of the test ore block

The thickness of the ore body is 0.6-1.6m, the inclination angle is 6-15°, the inclination length is 56m, and the strike width is 8-20m. The ore is moderately stable with an average grade of 8.5 g/t. The top and bottom plates are altered gneiss and are moderately stable. The ore body is in contact with the roof plate, and there is no large fracture structure damage in the ore block.

(2) Precision cutting work

The mining of the test nugget is extremely simple. The original prospecting roadway can be basically used. The 1401m alley can be used as the transport roadway. The prospecting mountain can be used as the main ramp. The upper prospecting level can be used as the return airway, only in the lower part of the ore body. At the office, digging the 5m contact road to return to the return airway of the lower mine.

Cutting is also very simple. For each mine, the road is excavated from the mountain to the boundary of the mine. The specification is 2m×2m. The uphill and the road are supported by bolts with a mesh of 0.8~1.0m ² /root.

(3) Mining work

The ore body of the uppermost mine is thinner, only 0.6m, and is extracted by extraction method. The mining volume of the remaining mines is about 1.7m.

In the order from top to bottom, the sides of the mine entrance are expanded to the boundary of the mine, and then the discontinuous pillars are formed. The roof of the mine is supported by bolts with a length of 1.6 to 1.8 m and a netness of 0.8 to 1.0 m ² /root.

The 7555 rock drilling machine for rock drilling has a hole depth of 1.6 to 1.8 m and a 0.8 m spacing. The ore is first transported to the mountain with a 5.5 kW electric raft, and then transported to the transportation lane with a 13 kW electric shovel.

After mining, the exposed area of ​​the mine has reached 110-170m ² . Residual pillars account for 16% of the total recovery area. The ore loss (mainly remaining in the bottom plate) recovered from the mine is about 1% to 2%. The total ore recovery rate of the whole ore block is 83%.

The ore depletion rate cannot be calculated because it has not been tested by the ore sample. However, according to the on-site observation, the roof did not fall and the ore remained without any ore. Due to the softness of the floor rock, the large bucket of the main ramp destroyed the floor into the ore. The depth of the enthalpy is about 0.5m, and the estimated ore depletion rate is about 5.7%.

Test the mining state of the ore block, as shown in Figure 1.

Fig.1 Zhangjiakou gold mine thin ore vein test method

Three months after the mining of mines II and III, due to the destruction of local geological structures, the two collapsed and the caving patterns were basically similar (Fig. 2). The smooth slope formed by the triangle at the top of the trail is very obvious due to the local structure. The range of the fall is limited by the pillars on both sides, and the pillar is not under pressure. According to this, the pillars are necessary measures to control the falling range and prevent the large surface from collapsing. The other two mines, due to the small exposed area, have good roof integrity and are still in a stable state after 10 months of exposure.

Figure 2 Schematic diagram of the local roof

A—mine area II caving area; b—mine room III caving area

1—mineral column; 2—asp.

Fourth, medium and thick ore body room column mining method test

(1) Technical conditions for mining ore mining

The test nugget is a quartz vein type deposit with an area of ​​753 m ² , a buried depth of 50 to 60 m, an average thickness of 5.2 m and a dip angle of 6 to 15 °. There are F ¹⁶ and F ¹⁷ fault interspersed in the nugget. Ore and surrounding rock alteration and weathering are serious, joint fissures are very developed, and stability is poor.

The average grade of ore is 3.62g/t. The shape of the ore block is a large and small inverted triangle, which is not conducive to the layout of the roadway. In addition, the test ore block is located near the inclined shaft of the inclined shaft, the lower part of the ore block (1357m) and the upper part (1370m) of the roadway, which bears the transportation and ventilation tasks of the whole pit, and needs to be topped and protected by the bottom column.

(2) Structural parameters of the ore block

The test nugget has a vertical height of 13m, a slant length of 42m, a mine width of 4~12m (estimated to be 5m), and a mine room with a discontinuous pillar of 5m×5m and a spacing of 5~8m. It is estimated that the maximum load of the pillar subjected to the overburden is 5.0-6.0 MPa, and the aspect ratio of the pillar is 0.6-1.2. Therefore, the pillar has greater strength and stability.

In order to protect the upper and lower roadways, the top and bottom columns are 4m and 6m respectively.

(3) Approved arrangement

In order to avoid affecting the 1357m main roadway, the tunnel is transported from the roadway to the bottom of the test block, and the chute and the mine are connected to the mines. From the lower end of each mine to the upper end, the patio is cut vertically to the roof of the ore body, and the crossroads are cut under the roof to the boundary of the mine, and the mines are penetrated to facilitate pedestrians and small electric eels, and the lower end of each mine is excavated. Electric winch winch chamber. Under the roof, shallowly cut the roadway from the center of each mine and connect it with the 1370m roadway.

The total length of the mining roadway is 167.6m, and the mining ratio is 18.7m/kt.

(4) Cutting work

The cutting well and the cutting cross-section are used as free faces, and the shallow holes are used for mining and expanding to open a cutting groove of 1.5 m width. The ore is taken and slipped to the lower part of the mine.

The cutting roadway is used as a free surface, and a shallow hole is used to form a 2m high top layer from the side of the cutting groove. The ore is transported to the lower part of the mine with 5.5kW electric pick.

(5) Mining work

As the cutting work progresses, the anchor or anchor is immediately installed with a metal mesh. The anchor depth is 1.8 to 2.0 m and the mesh is 0.53 m ² /root. Each metal mesh is 20m long, 1m wide, 5cm×5cm or 3cm×3cm, and the adjacent metal mesh is 5~10cm. The bolt support area only accounts for 46% to 93% of the exposed area of ​​the mine.

Press to the step 2m × 2.5m (height × width) for mining. Use a 7655 rock drill to make a horizontal hole with a hole depth of 1.8 to 2.0 m. With No. 2 rock explosive, the non-conducting squib detonated, the ore blasting was very good, and the mining efficiency was high.

The ore is taken to the lower part of the mine by the weight of the ore. The mines I and II are transported to the chute by 15kW and 28kW electric picks. The mines III and IV are directly transported to the chute with 28kW electric picks.

All mines can form a through-flow and have good ventilation.

Most of the mines have localized natural landslides due to direct delamination of the roof for 1 to 2 months after harvest. The mining sequence is carried out from the upper part to the lower part of the mine (ie from I to IV), making it easy to close the gob.

The roof support of the test ore block is shown in Figure 3.

Figure 3 Schematic diagram of roof support

(6) Roof reinforcement effect

A total of 6 flash roof landslides occurred in the test nuggets, two of which occurred at the end of mining III and IV mining, and the other four occurred after the mining end of mining or shortly after the recovery of the mine. See Table 1 for roof collapse.

Table 1 Statistics on roof caving of each mine

In the range of cutting the top, basically all of them are supported by bolts or bolts and metal mesh to ensure the safe and normal mining of the mine. After mining some of the pillars, the exposed area of ​​the roof is enlarged and the reinforcement cannot be supplemented. In this case, it is an inevitable phenomenon that the roof falls.

In the test site, the broken roof and its exposed area are 80-160 m ² . After the bolts and anchors are added to the metal mesh to support the roof for 42-86 days, the roof is partially collapsed. The normal recovery time is only 10 to 15 days (including the recovery of some of the pillars), while the time for cutting and supporting the roof is 27 to 32 days. Therefore, the cutting and supporting process should be improved to improve its speed and quality. At the same time, according to the stability of the roof and in a reasonable order, the possibility of recovery of the pillar and the amount of recovery should be determined, and the roof reinforcement effect is more obvious. The safety of top and back mining operations is guaranteed.

V. Main technical and economic indicators and evaluation of test results

The main technical and economic indicators obtained by the thin ore body and medium-thick ore body-pillar mining method test nuggets are listed in Table 2.

Table 2 Main technical and economic indicators of the test block of the room and pillar mining method

From the results of the two ore test results, the following conclusions can be drawn:

(1) For the thin ore body condition of the stable roof with less damage to the top plate, leaving 10% to 15% of the regular ore column, and controlling the exposed area of ​​the roof of the mine to 150-200 m ² , The mortar anchor fully supports the mine, the network degree is 1.0~1.2m ² /root, and the anchor depth is not less than 1.6m, which can ensure the normal mining of the mine safely.

(2) For medium-thick ore bodies with poor roof stability, the room-column mining method can be successfully applied on the premise of good roof control. The method of controlling the roof is: 1 During the mining period of the mine, it is necessary to maintain an appropriate amount of pillars to bear the load of the overburden (the proportion of the pillar is about 20%, the aspect ratio is 0.6 to 1.2), and each mine should be controlled. The exposed area of ​​the roof is not more than 150m; 2 after the roof is cut, it should be fully supported by bolts and bolts and metal mesh in time; 3 improve the topping, support and recovery strength, so that the roof exposure time does not exceed 30d.

(3) After the mining of the mining house is completed, according to the stability of the roof, the possibility of partially recovering the pillar and the amount of returning mining shall be determined. At the same time, the mining column shall be returned in a reasonable order to improve the recovery rate and the mining house shall be closed. The gob area is treated by a local natural slumping method.