Becker's copper mine borehole blasting - underground heap leaching example (USA)

The mine is a lentil-like ore body with an inclination of 50°, a length of about 200m and a thickness of 100m. It extends 100m from the ground. The reserve is 100,000 tons of Cu10.0% block sulphide ore and 700,000 tons of Cu 2.0% mixed mine. The former has been harvested from open pit mines, and the latter has 475,000 tons left at the bottom of the pit and slope. Under the help, it is not suitable for exposure, but the impregnation is good. Therefore, it is decided to use the drilling and blasting to make the necessary permeability after loosening, and then carry out underground heap leaching. The total length of the hole is about 7000m, and the hole diameter is 146.229 and 251mm. Among them, there are 175 holes and ø229mm inclined holes in the pit (the hole is inclined at 3 to 35°), accounting for 70%; the hole diameter varies depending on the hole diameter, ø229mm The above borehole is 7×7.7m, the following is 3.3×3.3m, the hole depth is 13.3～92m; the blasthole above the groundwater level is filled with ammonium nitrate explosive, the following blasthole is equipped with high-density water-gel explosive; the instantaneous power generation detonator is used to pass the hole The bottom is detonated, and two sets of detonating lines and parallel detonating cords are used to detonate to prevent the guns. The total charge is 181t and the blasting rock is about 580,000 tons. After the explosion, a heap with an average block size of 230 mm was formed underground, with an average of 1.18% Cu. Divide it into four steps of different sizes, flatten out and open the furrows, and then cloth. The immersion liquid is a replacement tail liquid, pH=1.6-2.0, and the ø150mm main pipe is used for infusion, the branch pipe is ø50mm polyvinyl chloride tube, and the nozzle is mounted. The cloth liquid flow rate is 662 to 757 L/min. The rich liquid is merged into the bottom of the pit, and the ø406mm and 54m deep liquid collecting well drilled through the mine is lined with a stainless steel casing with a wall thickness of 6.35mm and ø330mm. The 17m long pipe wall has a mesh hole. Let the solution pass. A 29.8kW, 660L displacement 10 grade stainless steel pump is installed in the well to extract the rich liquid. The rich liquid contains Cu1~2g/L. The original design of the project is 2270kg of copper per day and the service period is 5 years. The sponge copper was recovered 3175t twice before and after the operation, and the total recovery rate was 25%. The investment has been fully recovered within 6 months.

The underground heap leaching diagram of the Bickmaker copper mine is shown in Figure 1.

Figure 1 Schematic diagram of underground heap leaching of Bickike copper mine

1- Section view of the pit before blasting; 2- Rain bird nozzle; 3- Taihang section after blasting;

4-rich liquid well; 5-burst hole; 6-blast boundary line