The average thickness of the coal mine ore Yellowstone Hubei Liushugou Mining Co. Dingxi phosphorus ore 3.5m, the average grade of ore 30% P2O5. However, the faults and joints in this area are extremely developed. The surface involves structures such as houses, roads, rivers, etc., and the area is close to the market town, and the surface is not allowed to have large deformation. Therefore, the mining rate of mining in the area using the room and pillar method is only 60% to 65%. In order to improve the resource utilization rate, the prefabricated top section tailings filling mining method of the mast is proposed and researched to achieve the purpose of controlling the goaf and using mineral resources efficiently. The thickness H2 of the water-conducting fracture zone is: Where m' is the average thickness of the nugget. In order to reduce the disturbance of the mining layer to the surface, it is mainly considered to determine the average load of the overburden by using the cumulative thickness of the caving zone and the water-conducting fracture zone: Where r is the average weight of the two bands; H is the average thickness of the two bands; S is the maximum exposed area of ​​the empty field. Where c is the spacing of the cutting tunnel; a, b is the width and length of the reserved pillar when designing the mining; R is the average weight of the overburden; h is the average thickness of the rock from the roof to the surface. According to formula (5), the maximum spacing of the masts can be calculated to be 8.33m. Then the average stress δP of the pillar is: Where γ is the column bulk density, N/m3; H1 is the overburden height; LP and BP are the length and width of the pillar; L0 and B0 are the length and width of the pillar spacing. Where, SP is the strength of the pillar; δc is the uniaxial compressive strength of the pillar material; BP is the pillar width; h1 is the pillar height; Bph1 is the pillar width to height ratio; n is a constant, when the pillar width When the height ratio is >5, n=1.4; when the aspect ratio of the pillar is <5, n=1. If the safety factor of the pillar is K, then: According to the original house column method, the spacing of the pillars is 12m, the inclination is 9m, the length of the pillar is 6m and the width is 4m. According to the mining method, the spacing of the columns is 8m, the inclination is 6m, and the length and width of the columns are 4m. Calculate the safety factor Kç ¼ column and K-mine column of the pillar separately, and obtain: Kç ¼ column>K pillar. Vacuum Cleaner,Cordless Vacuum,Handheld Vacuum,Stick Vacuum GUANGDONG DEERMA TECHNOLOGY CO., LTD. , https://www.fsdeerma.com
1 Geological overview and mining technical conditions
The mining area is located in the sedimentary caprock area of ​​the northern part of the Huangling anticline. It is located in the west of the Dingjiahe mining area of ​​Yichang Phosphate Mine. The stratum tends to the east to the north, with a dip angle of 2°-8°. It is a gentle monoclinic structure with no obvious folds, faults and joint development. .
The excavation strata in the mining area include the former Sinian ridge group, the Sinian system of the Doushantuo Formation (Z2d) and the Dengying Formation (Z2dn), and the industrial layer Ph13 is located in the Doushantuo Formation. The direct roof of Ph13 deposit is Z2d13 block-like powdered dolomite , and the bottom plate is containing potassium shale . The ore layer has a gradual transition relationship with the top and bottom.
The regional hydrogeological conditions are of a simple type. The main surface water flow is the Xichong River, which is the branch of the Huangbai River system. The underground karst water is not developed, and the fissure water is the main. The engineering geological type is a hard, semi-hard rock formation with simple to medium engineering geological conditions. The test nuggets are 116m long along the strike, with an average width of about 60m and a total block area of ​​7900m2.
2 mining methods
The mining method is divided into two stages: mast pre-control top and tailings filling and mining. The pre-control top stage of the mast is divided into two steps. The first step is to cut the column position of the mast in the mine. The column cutting width is 6m, and the continuous pillar is reserved for 6m in width. The second step is the construction of the column. After each column strip is cut, the column construction is carried out from top to bottom. The mast is a cylindrical structure with a diameter of 4 m, and the center distance is 10 m along the inclination (ie, along the direction of the column strip).
The second stage tailings dry filling mining is divided into two steps. The first step is to recover the 6m zone reserved between the columns after the completion of the column curing period. The second step is completed after each mining ore zone, empty field immediately dry-filled using beneficiation plant tailings. The order of implementation of the two phases is shown in Figure 1. 
3 mast design
3.1 column spacing
According to the three-band law of the surrounding rock movement failure, there are a falling belt, a fractured water guiding belt and a curved sinking belt. According to the empirical formula, the thickness H1 of the fall belt is:
According to the pillar-supported area theory, the average load on the overlying strata of the pillar is:
Substituting the column for the column, the load capacity of the column is assumed to be the average load of the overburden, and the density of the column is:
3.2 column size
From the perspective of maintaining the stability of the stope, the spacing of the pillars should be less than the limit span of the mine, and the cross-sectional dimension of the pillar itself should meet the bearing capacity requirements. Therefore, the pillar size can be determined by its compressive strength. According to the theory of area bearing capacity, it is assumed that the gravity of the overlying strata is evenly distributed according to the area, and the pillar supports the gravity of the overlying rock pillar. The bottom area of ​​the rock pillar is the sum of the mining area allocated by the rock pillar and the area of ​​the pillar itself.
The strength of the pillar depends mainly on the uniaxial compressive strength of the pillar and is related to the shape and size of the pillar. According to previous studies, the pillar strength can be calculated by formula (7):
There are no structural planes such as joints commonly found in the original pillars in the concrete pillars, the strength is high, and the concrete texture is relatively uniform. The main bearing capacity of the pillars is subjected to axial pressure. According to the principle of mechanical properties, the 4m×4m square pillars and the diameter of 4m Cylindrical masts have little difference in the ability to withstand axial pressure, while cylindrical masts save material, and are easy to support and cast.
Considering the factors such as the bearing pressure of the mast, the mining safety factor, the material cost, the ease of construction, and the construction progress, it is determined that a cylindrical concrete column with a diameter of 4 m is used.
4 Economic and social benefits analysis
(1) The total area of ​​the test area is 7900 m2, the average thickness of the ore layer is 3.5 m, the ore specific gravity is 2.8 t/m3, and 66 columns are designed. According to the design of the house and pillar method, the actual amount of mine returned is M1≈50323t, and the actual loss of mine M is '≈27097t. According to the pre-control top-slump tailings filling mining method of the mast, the recovery rate of the ore block tends to 100%, and the mined amount M2≈77420t is expected to be mined. Compared with the original mining method, the ore-producing amount can be 27097t.
(2) According to the local actual situation, the cost of the column is about 300 yuan/m3, and the total cost of the column is W≈87 million. According to the existing phosphate market, the net profit of 1t ore is about 200 yuan. According to the mining method, the mining test area is expected to generate a profit of 5.42 million yuan. After deducting the cost of the column, it is expected to create a net profit of 4.55 million yuan for the company. Mining using this method is expected to consume about 25,000 m3 of tailings from the concentrator, reducing the cost of land acquisition, construction and post-treatment of the ground tailings pond.
(3) Using the filling method to recover the resources, the utilization rate of resources can be improved, and the service life of the mine can be extended. Moreover, the goaf filling and topping can effectively alleviate the large-area caving hazard in the goaf, reduce the deformation and damage of the mining surface environment, and reduce the occurrence of geological disasters.
5 Conclusion
(1) Through the pre-control top-section tailings filling mining test of the mast, the diameter of 4m is obtained, and the distance from the center to the center is 12m. The support of the mast along the inclined center is better than the original pillar. Ensuring the safe operation of the second-stage mining and dry-end dry filling of empty tails increases the safety factor of mining operations.
(2) Using the pre-controlled top section tailings filling mining method of the mast, the first stage mast construction and the second stage empty section tail sand dry filling can improve the resource utilization rate of the test area by 30% to 35%, and is effective The disposal of the goaf has increased the economic benefits of the enterprise.
(3) The prefabricated top section tailings filling mining method of the mast can be adjusted according to the actual conditions of different mines, and the spacing and size of the column are properly adjusted, which has a good prospect of popularization and application.
references:
[1] Tian Xuheng, Chen Faji, Long Xiucai. The application of the mast roof open-pit mining method in mining gently inclined ore bodies [J]. Mining Technology, 2008, 8(6): 11-12.
[2] Yang Xiuming. Study on replacement of primary ore column with mast column [J]. Mining Technology, 2011, 11(4): 25-27, 50.
[3] Ma Yushan, Wang Jianguo, et al. Experimental study on pre-controlled top segmental empty field tailings filling mining method [J]. Gold, 1999,20 (10): 13-17.
[4] Brady B. H. G. BrownE. T. Underground mining rock mechanics [M]. Yan Shigang, Zhu Wancheng, Zhao Wen, etc. Beijing: Science Press.
Article source: Mining Technology; 2017.12(1)
Author: Yu silver propionate, Tian Qi, Peng Shanyao; Liushugou Mining Group Hubei, Yichang, Hubei 443145
Copyright: