Mineral resources are the product of the earth’s crust in its long-term formation, development, and evolution process, and are formed by the aggregation of natural minerals acting under certain geological conditions. In the mining of underground mineral resources, different rock drilling and blasting mining processes are used according to the production status of the mine. In general, underground mining can be divided according to the depth of blast holes
1. Shallow hole rock drilling (hole depth 6m).
2. Medium and deep hole rock drilling (hole depth 10-30m).
3. Deep hole rock drilling (hole depth 50-60m).
Application of Rock Drilling Tools in Mining
In shallow hole rock drilling, for blast holes with a diameter of less than 43 mm, H22 mm tapered drill rods and chisel-type, cross-type, or button bits are usually used; for blast holes with a diameter greater than 43 mm, use R32-H25-R32×1000 mm or R32-D32-R32×1000 mm extension rod, cross-type or button bit. In medium and deep hole rock drilling, R32-D32-R32×1100 mm, 1200 mm extension rods are mainly used, with diameters of 55 mm and 60 mm cross bits and button bits, and T38-D38-T38, T45-D45-T45x1525 mm extension rod and MF rod, with diameters of 64mm, 76 mm button bit.
Deep hole rock drilling is mainly used for stage mining method, drilling deep horizontal holes or deep downward holes. The diameter of blast hole is usually more than 100mm, and the maximum can reach 165mm. High-pressure DTH drilling tools are usually used.
Application of Rock Bolts in Mining
Rock bolt is a rod-shaped body anchored inside a rock mass. The use of a rock bolt to support the roadway is when the roadway is drilled into the surrounding rock after excavation, then the rock bolt is installed in the hole of the bolt, and the surrounding rock of the roadway is artificially reinforced.
Rock bolts have many advantages: save pit wood and steel, reduce support costs, small excavation section, small roadway deformation, low maintenance costs, safe work, light weight, reduce physical labor, reduce ventilation resistance, conducive to lane construction and speed up the excavation, wide range of use, adaptable, reduce the amount of transport, conducive to the mine transportation and lifting. However, rock bolts cannot prevent the weathering of surrounding rocks and cannot completely prevent the spalling of rocks in the fissure between rock bolts and rock bolts. Therefore, rock bolts combined with other support measures, such as metal mesh, slurry spraying, or shotcrete, will achieve a better support effect.
Self-drilling Anchor Bolts in Mine Roadways with Soft Rock Formations
The principles of rock bolt support include suspension, composite beam, wedging, extrusion reinforcement arch, and span reduction.
Self-drilling anchor bolt is used to inject cement slurry into the fault fracture zone of the roadway so that the slurry fills the fault soft fracture zone, and the cement slurry solidifies to form a reinforced anchor nesting ring in the soft fractured rock layer, which increases the cohesion and internal friction angle of the rock, improves the strength and compressive capacity of the rock in the fault fracture zone of the roadway, and stops and controls the deformation of rock in the roadway under the joint action of the grouting anchor rod and the grouted surrounding rock.
The Process of Self-drilling Anchor Bolt in The Soft Rock Formation of The Mine Roadway
Self-drilling anchor bolts are grouted in the soft rock formation of the mine roadway, using a secondary grouting process. The first grouting is done while drilling, and the slurry water-cement ratio is about 1:1; the second grouting is after the self-drilling hollow anchor bolt is drilled to the design depth, and the slurry water-cement ratio is about 0.45~0.6:1. Both grouting are pressure grouting, which can make the grout fill the cracks of the rock mass, stabilize the internal structure of the broken rock mass, and enhance the anchoring force.
