Mining with sublevel caving mining method

The sub-column sublevel caving mining method generally uses medium or deep hole or deep hole falling ore. Commonly used YG-80 and YGZ-90 rock drills are equipped with FJY-24 ring ski-type gantry, drilling vertical fan-shaped blastholes, blasthole diameter 65~72mm, general hole depth 10~15m, minimum resistance line It is 1.5 to 2.0 m, and the blasting hole density coefficient is 1.0 to 1.2. In order to improve the quality of ore crushing, some mines have conducted experiments to increase the blasthole density coefficient and achieved good results. The medium and deep hole rock drilling efficiency is 20 to 25 meters per shift. The rock drilling equipment for drilling deep holes mainly uses the YQ-100 type down-the-hole drilling rig to drill horizontal fan-shaped blastholes or inclined fan-shaped blastholes. The diameter of the blasthole is 105-110mm, the hole depth is 15-20m, and the minimum resistance line is 2.5-3.5. m, the blasthole density coefficient is 1.0 to 1.2. The rock drilling efficiency is generally 5 to 7 meters per shift in the hard ore, and the soft ore can be drilled to 10 to 15 meters per shift. The highly efficient CTC-700 and CRQ-80 trackless self-propelled deep hole mining rigs, which have been widely used in the sublevel caving method, have not been used in the sublevel caving method. In the future, the layout of the mining should be improved in order to further improve the mechanization of the mining work and adopt high-efficiency mining equipment.

The extensive application of extrusion blasting technology has been proven to help improve the quality of ore crushing and reduce the bulk yield. According to the condition of obtaining compensation space by caving ore, it can be divided into two types: small compensation space extrusion blasting and extrusion blasting in the direction of caving rock (also called “lateral extrusion blasting”).

Small compensation space extrusion blasting, as shown in Figure 1. The compensation space required for the caving of the ore is to utilize the lane space in the caving mine and one or several small compensation spaces. The commonly used compensation space factor is 15-20%. Its advantages are flexibility and adaptability, generally not subject to changes in ore body shape, state of adjacent caving ore, size of one blasting range, stability of ore rock, etc.; engineering of adjacent ore blocks The damage to the blasthole is small; the quality of the ore crushing is guaranteed. The disadvantage is that the amount of precision cutting is large; the structure is complicated; the construction conditions are not good. Therefore, small compensation space extrusion blasting is generally used in the case of complex ore body shape, and the ore stability is poor, or combined with lateral extrusion blasting.

If the shape of the ore body is regular, it should be better to use the blasting to the caving ore direction, as shown in Figure 2. This method can save special compensation space and reduce the amount of cutting work. Each blasting relies on the impact force during blasting to squeeze the loose ore to obtain compensation space. Therefore, before each blasting, the ore that has collapsed in the previous stage needs to be loosened and oreed, and the ore-mining amount is about 15-20%. Each thickness of the caving is related to the thickness of the ore body, the thickness of the adjacent caving rock and its loose state. When the thickness of the ore body is less than 7~8m, the blasting is frequent due to the high clamping property and the small amount of collapse. It is generally not suitable. Usually, the thickness of a single collapse should be less than the thickness of the ore body and the thickness of the adjacent collapse. The thickness of the adjacent caving rock and its loose state must ensure sufficient squeezing depth and displacement width during blasting to obtain good blasting effect.

The mining operations include three items: mining, secondary crushing and mining. In China, mines with sub-column sublevel caving are basically used for electric ore mining. The electric raft with a winch power of 30kw and a bucket capacity of 0.3m ^{3 is} the most widely used. A few mines use a 55kw electric winch with a bucket capacity of 0.5m ³ . The transport distance is generally 30 to 50 m. About 70-80% of the ore that has collapsed is released under the cover of the surrounding rock. Therefore, it is necessary to strengthen the management of the ore, control the state of the contact surface of the ore and its change in the spatial position, which reduces the ore in the process of the ore. Loss and depletion are extremely important.

Electric roadway maintenance. The production practice in the past 20 years shows that due to the large ground pressure and frequent secondary crushing and the impact of the bucket, the support of the electric roadway is often destroyed during the mining process, so it is necessary to strengthen the maintenance work of the electric roadway. . When carrying out the mining blasting, the support of the electric roadway must be temporarily strengthened. If it falls during the mining process, it should be repaired in time. Using wooden scraper roadway support and supporting the metal stent, the stent usually taken individually replacement method, when the stent have all been severely damaged, it must be completely renovated; concreting using shotcrete or electrical rake roadway, generally Sprayed concrete is used for spraying, so that the cracked concrete is bridged and re-supported.