Empty field method recovery mining top pillar

Figure 1 is an example of the recovery of the top and bottom columns by the open field method. The top and bottom columns are 14 to 20 m high, and the upper and lower mine houses have been cemented and filled. The strength of the backfill is expected to be R ₂₈ = 3 ~ 4MPa, according to the measured top and bottom column has reached 10MPa. The mining work included digging a pedestrian ventilated patio to the transport level in the lower part of the column, and digging a slip mine to the electric ramp level. The electric roadway is excavated in the surrounding rock of the lower plate, and its position should be able to control the mining of all the top and bottom columns. A single-sided funnel is arranged from the electric roadway. The cutting groove is pulled out on one side of the top and bottom column, and the ore is mined in the upper fan-shaped hole. After mining, it is filled with cementing material to facilitate the recovery of adjacent top and bottom columns in the same stage. The horizontal length of the filling body is 30 to 40 m, and the natural collapse does not occur when the width is 10 to 15 m.

Figure 1 Empty field mining method mining top and bottom column

1-distribution funnel; 2-mining field; 3-way partition wall; 4-column;

5--cemented filling mine; 6-耙 mine roadway; 7-ventilated pedestrian patio; 8--minening well

FIG 2 is an example of lead zinc ore Huangshaping Kobo column method employing a pillar mining. Huangshaping Lead to a high temperature to mesothermal fracture filling and replacement lead-zinc multi-metal deposit, ore mining industry have more than two hundred. The ore body has a length of 40-280 m, a thickness of 1 to 70 m, an average of 5 to 20 m, and a dip angle of 40 to 80 °. The ore body has a variety of shapes and complex shapes. The ore is generally more stable. Most of the upper plate is limestone, which is relatively stable, but the sand shale is not stable, and the lower disc dolomite and quartzite rock are stable.

Figure 2 Artificial room column method mining bottom column

1-concrete cemented surface; 2-filled body; 3-filled well; 4-concrete column; 5-iteral column;

6-concrete partition wall; 7-slide mine; 8-side walkway; 9-reinforced concrete floor;

10-bottom column; 11-artificial rock column; 12-upper stope bottom boundary

The mine mainly adopts the dry filling method of the upper horizontally layered concrete partition wall. When the horizontal thickness of the ore body is less than 15~20m, the stope is arranged along the strike, the length of the mine is 30~50m; when it is larger than 15~20m, it is arranged vertically, and the width of the mine is 10~20m. The width of the column is 7~8m, and the height of the bottom column is 5~6m. If it is necessary to protect the transportation and ventilation of the upper stage, leave the 4m top column.

The method of mining the column is the same as that of the mine. After the column is pulled down, water is poured on the bottom column. 0.4 to 0.5 m thick reinforced concrete bottom plate, main rib ø12 ~ 18mm, secondary rib ø6 ~ 8mm, mesh degree is 200 × 250mm or 250 × 250mm. The bottom plate is embedded around the pillars by 0.5 to 0.7 m around the pillar. Rock drilling with the YSP-45 type up rock drill requires a concrete partition wall of 0.5m or more for the blast hole distance (filling the concrete partition wall with a thickness of 0.3m between the mine house and the inter-column). The layer height is 1.5 to 1.8 m, and a concrete backing plate of 0.2 to 0.3 m is poured on each layer of the filling material.

The top column mining method is the same as that of the mining room (dry filling, 0.2~0.3m thick concrete cushion on each layer of filling). The bottom column is divided into two layers for recovery. After the first layer is recovered, a concrete column with a diameter of 3 m is constructed, and the column spacing is 7 to 9 m, which is placed as low as possible in the ore. When the second layer is taken up, the ore on the concrete column is left as a pillar. Practice has proved that the artificial false roof of the upper concrete can be exposed to a large area and time when the rock pillars are tightly combined (the 180m ² exposure is not peeled off for 2 years), and the false top is easily damaged. In order to strengthen the support, a triangular prism of 0.6 to 1.0 m is left around the bottom column. A second hierarchical blasthole is drilled, and then to the outlet chute and security receding points and blasting ore in the entire area of the pillar with the YSP-45 to the drilling machine. It is required that the blasthole is 0.8~1.0m away from the stope and 0.6m away from the ore pillar. The bottom of the hole is 0.5m away from the reinforced concrete false roof, and the number of blasting holes is not more than 30. The top and bottom columns are taken back before the column. For more than ten years, the mine has used this method to recover more than 300,000 tons of ore from the top and bottom columns. The effect is good, and the relevant indicators are close to the mine. The ore loss rate is 8.8%, the depletion rate is 12.2%, and the direct mining cost is 7 yuan/ton. The disadvantage is that the amount of labor for pouring concrete columns is large.

The above two cases show that if the ore is stable, the strength of the upper filling body or the artificial bottom column is sufficient, it is possible to use the empty field method to return to the mining column, and better technical and economic indicators can be obtained.