Mining method in deep mining
Second, priority is given to mining methods with low depletion rate or for sorting and recovery, in order to improve the original ore grade and reduce the amount of lifting.
3. When determining the mining method, the exposed area of ​​the goaf should not be too large, so as to avoid the sudden fall of the exposed rock formation; sometimes, in order to ensure the exposed area of ​​the goaf in order to ensure the production capacity of the nugget, pre-reinforced long anchors may be considered. Technical measures such as cable to strengthen the rock formation.
Fourth, leaving no affect various types of roof slate stone pillars uniform sinking. Because these pillars cause stress concentration, rockburst occurs. Mining methods that can form continuous goafs must be used.
5. The mining method must be selected from the point where the elastic strain energy is accumulated at an angle close to the release energy from the recovery process, or from the slowing of the release rate of the accumulated energy. Therefore, a mining method suitable for ore rock conditions can be selected from the caving method or the filling method. In the Soviet Union, the sloping and steeply inclined ore bodies with large burial depth and ore and surrounding rock are not stable, such as the Krivorog mining area.
When choosing a mining method for deep deposits, you can draw on many of the experience of transferring from shallow deposits to deep deposits. When the open-field mining method used in shallow opening is transferred to deep mining, the increase of ground pressure will cause some pillars to be destroyed, and the roof (or two plates) will fall, which will cause difficulties in the mining work. To overcome these difficulties, the following technical measures can be taken:
First, reduce the size of the mine, and increase the size of the pillar. For example Shizuizi copper ore from the top of the stage Bikeng 25m, a depth of 950m, always shallow hole Shrinkage Method. Good results are obtained in medium depth (above 530 m) mining. As the mining depth increases (530-710m), the mine pressure increases, and the conditions of mining operations become increasingly difficult. For this reason, the structural parameters of the ore block are changed accordingly. The mining method of the mining house and the pillar is based on specific conditions. The mineralization method variant has basically achieved satisfactory results. However, below 710m and stage, due to the excessive pressure in the deep, the mineralization method variant can not completely solve the difficulty of roof management in deep mining, which makes the mouth unable to guarantee, the pillar is difficult to recover, and the loss is too high. The practice of the mine shows that when the mining depth is 710 ~ 950m, it is not suitable to use the retention method. For example, the Flinfrun Copper Mine in Canada adopts the deep hole mining stage mining method, which makes the mineral amount in the pillar reach 1/3.
Second, change the mining method. The moderately inclined gold deposit with a dip angle of 21° is mined in the Witwatersrand mine in South Africa. When the mining depth is less than 300 m, the full mining method of the retained column is adopted. After the mining depth exceeds 300-400 m, the total proportion of the retained column is reduced. The proportion of the wall mining method in which the working face is continuously propelled in a line-filling arrangement is gradually increasing.
For example, the Pesma copper mine, which has a history of more than 100 years of mining in the Soviet Union, has been using the problem of the mining method of the cross-pillars to the ladders in the past. From 1910 to 1915, it was impossible to carry out the mining work by using the up-slope cross-supporting mining method. . Had to use the shallow hole retention method. After the mining depth was further increased, due to the large-scale rock movement, the vegetable in the recovery stage became a large supporting pressure belt, and the recovery work could not be maintained normally. Therefore, the filling mining method was adopted from 1947.
When some gold mines in Canada are less than 500-600 m deep, almost all of them use the method of retention, but when the mining depth exceeds 500-600 m, they all use the filling mining method.
3. Long anchor cable is pre-reinforced and filled once after mining. The Canadian birch mine uses large-diameter deep-hole mining in the deep part, with a stage height of 121m and a length of 35.5m. The upper part of the stope is pre-reinforced with long anchor cables, and the mining roadway is supported by spray anchors and 3.8m3 scraper. The mine has achieved good results.
Fourth, improve the use of the caving method. In deep mining, the main problems of applying the caving method are as follows:
(1) When the mining reaches a certain depth and the original rock stress increases to a certain value, the outflowing roadway at the bottom of the ore block is unstable. It is often uneconomical to reinforce the roadway to ensure its stability, which determines that the caving method has An effective depth of use. The effective depth of use depends on the thickness of the mining body. When the thickness of the ore body is 100m, the critical depth for reasonable use is 1400-1500m; when the thickness is less than 100m, the critical depth of use is 1800-2000m. When the mining depth exceeds the critical depth of use, the cement filling method should be used instead.
(2) The ore that has collapsed is compacted, causing difficulties in mine release and an increase in depletion indicators. The following measures can be taken to improve the use effect of the caving method: 10 to 15% of the caving ore is partially released on the whole panel area to loosen the ore and improve the ore-mining conditions; the ore roadway in the adjacent panel remains fixed (1) /2 segment high) height difference.
Through the analysis of many mine experiences that have been transferred to deep deposits and the evolution of mining methods used, it is known that the open field method and the caving method are difficult to continue to use in deep mining, and the filling method is the most effective mining method for mining deep deposits. For example, the Gifford mine in the Goral gold mine in India is one of the deepest wellbore in the world, with an opening depth of 3,260 m, mainly using filling methods. Canada's deepest mine, Kreisin Nickel , No. 9 shaft, with a depth of 2,175 m, is also mainly mined by filling.
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