The G-paste group of gypsum mining in Lvyang Rongguan area, V paste is layered in the Lower Cambrian alkali plant group, the maximum thickness of the paste layer is 5m, the minimum is 2.5m, the average is 4m, the block structure is grayish white. The hardness f = 2 to 4 and the density is 2.6 t/m3. V paste directly on top of 10m thick limestone, the lower part of which is 0.7-1.3m thick thin layered argillaceous limestone, relatively broken; the upper part is 6.1m thick gray black fine clastic limestone with flushing surface; bottom plate It is a 5.5m thick braided, finely crumpled black-gray dolomitic limestone with hard, bedding and joints.
1 mining method selection
The choice of mining methods has a direct impact on the safe production of mines, labor efficiency, ore quality, mining costs and recovery of mineral resources [1]. Most of the minefields are located under the village and the surface is not allowed to collapse. Therefore, mining by the room and pillar method. According to the occurrence of the ore body, the ore blocks are divided along the strike. The long axis of the mine is arranged along the inclined direction of the ore body, the mine is advanced along the strike, and the mine room supports the roof with continuous pillars.
2 stop formation elements
2.1 working face length
Reasonable working face length is an important condition for achieving high yield and high efficiency. According to the conditions of the plaster layer, the condition of the roof and the economic and technical factors, the roadway has a moderate tunneling rate, the lowest cost of the tonnage, and the equipment efficiency can be fully utilized to determine the economy. The best working face length. Because the average thickness of the paste layer is 4m, the blasting cream is used, the layer mining is carried out, and the 2DJP-55 type antimony winch is mined. At the same time, due to the large workload of support and open top, the working face is too long, which will affect the propulsion speed. It is difficult to control, therefore, the working face length is determined to be 70m.
2.2 Mine span
The roof of the stope is assumed to be a fixed beam, and the theory of material mechanics is applied. According to the rock beam hypothesis, the maximum allowable span of the roof is derived. The empirical formula is
Where Ls is the safety span, m; h is the thickness of the rock beam, taking 22m; RT is the tensile strength of the rock, 3.55MPa; n is the transverse fracture safety factor of the rock, taking 6; q is the rock beam load, q=Hγ =15.86MPa, H is the depth of the upper rock, taking 610m, γ is the rock bulk density, 26kN/m3.
Calculated as Ls = 6m. Considering the actual conditions of the roof and other factors, the mining width of the mine is determined to be 6m.
2.3 pillar width
According to empirical formula
Where a is the width of the retained pillar, m; b is the width, 6 m; S is the loss rate due to the retention of the strip-shaped pillar; γ is the average bulk density of the upper rock, 26 kN/m3; H is Mining depth, 610m; Rc is the allowable compressive strength of gypsum, 32MPa.
Calculated as S ≥ 0.495625, a = 5.896m. Considering the actual situation of reducing the width of the pillar after the two gangs of the mine in the mining of the V-paste group, the width of the pillar is 6m.
Based on the above analysis, it is determined that the ore length is 70m, the stage vertical height is 14.5m, the mining room width is 6m, the pillar width is 6m, the mining 6m is 6m, and the upper and lower sections are all 2.5s wide. 3m, do not leave the bottom layer.
3 mining cutting
The mining room adopts the method of moving forward to the pillars. According to the stability of the surrounding rock, it is conducive to the arrangement of mining machinery and equipment. The section of the section of the transportation lane is a three-hearted arch. The roadway is 3m wide, 2.8m high, and the tunneling area is 8m2. In the paste layer, the upper and lower sections are shoveled along the floor of the V-paste group, and the slope is 3‰. After the transportation and return airway are formed, an open-cut lane is drilled every 12m along the inclined floor. The opening cut is 2m wide and high. 2.2m, after the opening and cutting lanes are connected, a ventilation and production system is formed; after the opening and cutting eyes are penetrated, the roof is inspected every 5~8m along the direction of the cutting eye, and hits the gray-black banded argillaceous limestone in the roof. Drill, determine the thickness of the paste layer, and then determine the mining method according to the thickness of the paste layer.
4 mining process
Because the mining height is 3 to 5 m, the local maximum mining height is sometimes greater than 5 m. When the mining height is about 3 m, the total mining height is once. When the mining height is 4~5m, the upper and lower layers are mined.
Mining in full height mode: Starting from the lower part of the mine, the gap is first opened to form a step, the steps are arranged in an interlaced manner, and the working surface is formed by three steps on both sides of the center of the cutting eye. The height of the gang is 3m. , width 0.7 ~ 0.8m, lead borehole vertical direction to play 5, arranged along the two eyes paste layer capping the top plate, borehole depth 3m. The two gangs advance at the same time, and the step distance is 5m.
Layered mining: the thickness of the lower layer is 2.8-3.2m, which is mined by gangs; the upper layer is 1.7~2m thick and is mined by pressure top. The height of the space after mining and stratification is about 3m, and the height of the space after the top of the laminated roof (the volume after the rock is broken) will not block the head (the layer that is not topped) and affect the pedestrians and ventilation. The gangs are arranged in an interlaced step, which is pushed from the bottom to the top. The working surface forms three steps along the sides of the center of the cutting eye. The height of the gang is 2.8-3.2 m and the width is 0.6-0.7 m. Five blastholes are drilled in the direction, 3m deep, and the two gangs advance at the same time, and the step distance is 5m. Downward mining is used for mining stratification, which is pushed from top to bottom. The top is double-layered blasthole. The upper blasthole is blasted by single-stage air column. The depth of the eye is 2.5m, the eye distance is 0.8m, and each small shift is 2 cycles. In order to ensure the stability of the pillar and the roof, it is required to use a single-stage air column charge structure when arranging the eye and the top blasthole, so that the rock face after blasting is smooth and smooth.
Each working face is equipped with a 2DZP-55 type antimony winch to transport ore. The lower part of the mining room is equipped with a cornice. The ore is loaded into a fixed type mining car that transports the flat road. The mining capacity is 80t/shift.
5 top board management
The roof is controlled by the continuous pillars between the mines. Because the V-stacks are directly layered and sloping, the thin-layered argillaceous limestone is 0.7-1.3m thick, and the roof is relatively broken. Therefore, the anchor steel strip is adopted. Joint support roof. For local area reinforced support encryption according to the actual circumstances to add a bolt or a metal mesh.
5.1 support parameters
Mine roof bolt support density according to formula
Where n is the number of anchors in each row of the mine, and the root; M is the thickness of the easy-falling rock layer (paste layer), 1.3 m; L is the width of the easy-falling rock layer (paste layer), 6 m; B is the inclination of the anchor Row spacing, 1.2m; γ is the easy-to-fall rock layer (paste layer) bulk density, 27kN/m3; K is the safety factor, 1.5; t is the single anchor anchoring force, 100kN.
Calculate the number of anchors per row n = 3.8, take 4. Support parameters: bolt size is 22mm×2000mm, anchoring agent is 500mm resin roll, tray is 100mm×100mm×5mm steel plate, using equal strength nut; steel strip specification is 10mm×80mm×1200mm; metal mesh specification is 5m ×1m; the anchor and the top plate are laid at 75° to 90°.
5.2 support inspection
According to the formula
Where, G is the gravity of the rock suspended by the anchor, kN; M is the thickness of the easy-falling rock layer (paste layer), 1.3 m; L is the maximum support width, 1.2 m; B is the anchor row spacing, 1.2 m; The inclination of the rock layer is 13°; γ is the bulk density of the easy-falling rock layer (paste layer), 27kN/m3.
It is calculated that the gravity of the rock suspended by the anchor is G=50.6kN<100kN, which satisfies the requirements.
The exposed length of the anchor end shall not exceed 50mm; the mixing time of the medicine roll shall be strictly in accordance with the instructions; the medicine roll shall be evenly stirred, and the rock drill shall be removed after initial setting for 3 minutes. The joint support of the V-stack roof bolt steel strip is shown in Figure 1.
5.3 support effect
The strength of the resin anchoring agent increases rapidly, reaching 65% to 90% of the final strength after 30 minutes, and the final strength is 120 MPa. With resin anchor, the anchoring force can reach 100kN, which has the advantages of fast bearing, large anchoring force and high reliability. After returning to the mining room, the roof has a certain degree of fracture and sinking, but it remains intact and stable, which plays a role in reinforcing the roof. If the depth of the crushing area of ​​the roof is not large, there is no need to re-install the bolt, and the nut can be directly tightened to continue to use, without reducing the anchoring force and reducing the consumption of labor and materials. The use of waste steel wire rope to make steel strip can meet the production needs, and reduce the material cost, saving material costs of 350,000 yuan per year. Therefore, the use of equal strength anchor steel strip joint support has the advantages of simple process, convenient construction, low labor intensity and cost saving.
6 conclusion
The V-paste group is developed by the room-column method. The combination of full-height mining and layered mining has strong mining capacity and high efficiency. The roof is managed by the same strong anchor and steel strip support method, which can effectively control the roof of the mining face. The development of deformation, displacement and cracks increases the stability, safety and reliability of the roof, thus accumulating reliable experience for deep gypsum deposits and medium-thick gypsum mining processes and roof management.
references
[1] Xu Yongzhen. Mining science [M]. Xuzhou: China University of Mining and Technology Press, 2005
Sun Bo; Shenyang Company Hongyang Third Mine;
Zhang Zhenting, Sun Zhongsheng ; Shenmei (Group) Liaoyang Gypsum Mine;
Article source: "Modern Mines": 2016.2;
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