Example of non-metallic mining of building materials - Mengyin Diamond Mine

Diamond Mine No. 1 Mengyin Kimberlite red veins, angle of at least 80 °, ore average thickness of 0.37m, 1440m total length of the exposed surface, a small pulse 24 inclusive form en echelon arrangement similar. The stability of the ore body is poor. When it meets water and air, it is easy to absorb moisture and expand, so that the ore is broken, and it is easy to bond when stored for a long time. The surrounding rock is an ink-containing mica slanted gneiss . The lithology is hard, the layer is thick and not very developed. When the two small veins meet, the surrounding rock is generally broken.

The downward layered concrete roof mining method is used, as shown in Figure 1. The height of the stage is 40m. There is no digging for a patio every 40~50m. From the patio to the two sides, the mining is carried out from top to bottom. The height of each layer is 2.2~3.0m, and the maximum can be increased to 5m. According to the stability of the surrounding rock. And set. It is mined in the form of an access road under the protection of concrete shields. The width of the approach is 0.8-1.0m. The mine was discharged with a 4.5 kW electric raft. At the end of each layer of mining, immediately smooth the way and lay the steel mesh, and then lay a 100-150mm broken ore layer, and then pour the concrete to form a artificial top plate with a thickness of 0.25-0.3m. The concrete number is 150, the steel mesh is 300×300mm, the longitudinal steel bar is ф8～ф10mm, and the transverse steel bar is ф6mm. In order to make the concrete and the two sides can be firmly combined, the two walls must be cleaned before the concrete is poured and drilled between the two sides every 5m. Insert φ22～ф24mm, 400-500mm long scrap steel or round steel, leaving 150 at the outer end. ~200mm is poured into the concrete. The concrete is stirred on the ground and sent to the stope through the chute. The tamping is not required to be cured. Due to the need for ventilation, ventilation holes may be left in place on the concrete slab, and the guns are discharged into the upper goaf.

Figure 1 Downward layered concrete roof mining method

This mining method has obvious advantages compared with the shallow hole retention method, the subsection mining method and the sublevel caving mining method which have been used in the mine in the past. The recovery rate of the stope is over 98% and the depletion is stable. Even if the surrounding rock is broken, the stratification height can be reduced to ensure production safety, so the adaptability is strong. The disadvantage is that the production capacity of the stope is slightly lower (the monthly production capacity of the stope is 800-1000t). Considering the impact on mineral processing , the overall technical and economic effects are far superior to other methods. Figure 2 is a photo of the mined area after harvest.

Figure 2: Downward stratified concrete roof mining method