At present, the shallow mineral resources in the country are gradually depleted, and the deepening of mining depth has led to a more severe mining environment. The mining conditions of many deposits are complex and variable. The surface of a large number of mining wastes is heavily polluted, and the government is increasingly demanding environmental protection. 6]. As the filling method more commonly used metal mine mining method, its advantages in control of ground pressure and surface protection of the environment is increasingly widespread attention and application. According to the traditional mining method, the smaller the dip angle of the ore body, the more difficult the mining is. The use of the post-filling mining method in the gently inclined ore body can better solve the problem.
1 Mine Overview
Fe6 main seam of iron ore South Ming River is a medium-sized ore body, to the NE, the tendency SE, the tendency around 20 °. The shape of the ore body is relatively simple. It is high in the west and low in the east. It extends from the west to the east and extends deep. It is a long strip-like slope.
The ore layer itself has a dense structure, many dense and massive structures, and good stability. The ore body's elevation in the mining area is 159.5~-126.67m, the strike length is about 980m, the average thickness is about 14m, and the average grade TFe is 52.04%.
The Fe6 ore body is present on the contact zone between diorite and limestone (O3-22). The roof of the ore layer is mainly crystalline limestone. Due to the large recrystallized particles in the rock, the rock structure is loose, affected by structural changes, the fracture is relatively developed, and the groundwater activity, the karst is also developed, especially in the west of the 11# exploration line. The rock is broken and the stability is poor. Skarn plate and diopside of diorite skarn loose structure, poor stability, development of the ledge base plate 1 ~ 10m thick. The altered diorite is dense and has good stability and is the base plate of the deposit. However, in the west of the 11# line, the stability of the altered diorite is affected by the fault.
2 original mining methods and problems
Before March 2010, the Nanfeihe iron ore mine has been in a state of suspension. The main reason is that the long-term large-scale exposure of the goaf caused by the empty field method, coupled with mining under the riverbed, will result in the instability of the surrounding rock in the goaf. In the case of subsidence and cracking, the riverbed water enters the mining area through the fissures in large quantities, and there is no safety guarantee, which is more likely to threaten the safety of the Wannian Mine adjacent to the Nanfeihe Iron Mine. Later, shallow hole chambers were used to fill the mining method, but the filling times were numerous and the process was complicated. After each filling, it took a long curing time to enter the next mining operation cycle, resulting in increased costs and affected production capacity.
3 mining method improvement
There is Nanxun River (seasonal river) in the upper part of the west end of the ore body. The pressure of the riverbed is about 4.7 million tons. The remaining ore body above the level of -80m is located under the floodplain. Because the height difference is not large, it is not suitable for caving. According to the geological characteristics of the various sections of the deposit and the occurrence and shape of the ore body, and taking into account various influencing factors, the iron ore mine improved the production process in 2013, using a segmented empty field and post-filling mining method.
3.1 stope structure parameters
The stope is arranged along the strike, leaving 6m thick columns at the end (through the vein); along the inclination of the ore body, the nugget is 12~15m wide; the height is the vertical thickness of the ore body, and the segment height is 8m. The adjacent ore blocks are mined by a mining method, and the distance between the ore-mining roads is 10.8m. Each section shall be provided with an ore slipway along every 60 or 40 m (ie, each vein), and a waste rock drifting well shall be provided every 120 or 80 m (ie, every 2 veins), and each stage shall be along the strike direction every 120 or 80m (every 2 veins) set up a ventilated pedestrian well. Ore chute, waste rock chute, well ventilated pedestrians, are disposed in the segment drift bottom slate stone ore. The method of filling the mining after the segmented empty field is shown in Figure 1.

3.2 mining operations
Segmented rock drilling and segmental mining are adopted. Each segment in each phase is first taken down and then taken back. After the cutting trough is opened, the free surface of the mining can be formed to carry out a large amount of mining in the mining room. In the mine rock drilling alley, the Simba1354 rock drilling rig is equipped with a COP1838ME rock drill, and the vertical upward fan-shaped blasthole is drilled. The diameter of the hole is 76mm, the maximum hole depth is 35m; the row spacing is 2m, and the hole bottom distance is 2~. 2.5m. The ROCMEC charge vehicle is used to charge the drug, and the emulsified granular ammonium explosive is used. In order to ensure the blasting effect, the detonating tube and the detonating cord are used to detonate, and one or two rows of blastholes are blasted at one time.
3.3 mining
The output of the mining site is ADCY-3L electric scraper, the bucket capacity is 3m3, and 2 scrapers are arranged for every 3 stopes. The scraping distance is 15~120m. The ore is poured into the stope ore by the scraper, and is loaded into the mine car by the vibration discharge machine. It is transported to the main slide through the vein transport lane and is broken and raised from the main well to the surface. The ore block is limited to 500mm,
The oversized slabs are secondarily crushed in the mining approach using a mobile crusher. The loss rate and waste rock mixing rate are shown in Table 1.

3.4 ventilation
The fresh air flow enters the stopway from the upper and lower lining along the vein transportation lane, the vein, the ventilation pedestrian well, and the stopway. The dirty wind from the rock drilling and mining face is extracted from the ventilation pedestrian well to the upper return airway. Or the return air well), the surface is discharged by the return air inclined shaft and the return air shaft.
3.5 filling process
3.5.1 Process
(1) The whole tailings of the selected plant are transported by pressure to the filling standing silo by the pump, and naturally settle. Before the filling, the clarified water on the surface of the whole tailing sand is discharged, and the gas is used for pulping. After the whole tailing sand is uniformly homogenized in the sand bin, the sanding pipe is discharged, and the whole tail mortar is supplied to the mixer.
(2) The bulk cement powder is transported to the filling station, and is supplied to the mixer after being metered by the feeder and the electronic scale.
(3) The mixture of the whole tail mortar and the cement powder is uniformly stirred to prepare a filling slurry having structural flow characteristics, which is self-flowed to the gob filling through the filling drilling and the downhole conveying pipeline.
3.5.2 Filling ratio
The filling ratio of Nanfeihe iron ore mine is (1:4.5)～(1:12).
(1) The mining house for the first mining will be used as the secondary mining column, and the proportion of the filling slurry is required to be 1:6 (gelling powder: tailings).
(2) The mines entering the residual stage in some areas will be returned to the mining column again, requiring a filling slurry ratio of 1:8 (gelling powder: tailings).
(3) The last mining house enters the finishing stage and is no longer used as an empty field for returning to the mining column. The ratio of filling slurry is 1:12 (gelling powder: tailings).
(4) The bottom of the mine is the ore, and the bottom of the mine is used as the roof of the lower layer or immediately after the filling is completed. The forklift is required to be filled and the top layer is poured 1m. The proportion of the filling slurry is 1:4.5 (gel powder) : Tailings).
3.5.3 Pipe laying
There are 2 sets of filling pipelines in Nanfeihe Iron Mine, and the filling stations are filled with +40m horizontal filling lanes to reach various empty fields in 0m horizontal area; from 2 filling holes in +40m level 1# Xiaojinglian Lane to 0m level measures Lane, along the 2# through the ramp to reach the end of the -40m mid-section. The on-site layout of the filling pipeline is shown in Figure 2.

3.5.4 Mine network
After the mining of some mines is completed, the bottom plate is still ore. In order to improve the safety of the recovered floor ore, it is necessary to lay the net. Adopting 6mm steel bar, the mesh size of the steel mesh is 2m×8m, the mesh size is 200mm×200mm, the hooks of the longitudinal ribs and the horizontal ribs are facing away from the bottom plate, and each 2 meshes are connected by hooks, and each mesh is erected. 3  6mm × 1.2m steel bars.
3.5.5 top work
In order to ensure the filling body is topped, when the filling body in the stope is 0.5m from the height of the top plate, a cement expansion agent is added to cause the filling body to expand as much as possible. The filling body 28d has a strength greater than 2 MPa. The construction site of the blockage is shown in Figure 3. Filling the roof is shown in Figure 4.

3.5.6 Filling technical problems and solutions
3.5.6.1 Filling the top
For the stratified filling of the mine, a stratification of 10m in each stage, so that each stratification is connected with the lower mining room, the top one layer is dig into the filling lane, and the top of the mining room is connected to arrange the filling pipeline, thereby Ensure that each mine is able to fill the roof. Specific solutions: Firstly, due to the irregular shape of the ore body during mining, there are often high and low, uneven and uneven. When drilling the filling hole, the highest position must be found from the measured data, and then the filling hole is hit to the highest. In order to ensure the filling of the top; secondly, in the filling process must ensure that the water and air in the empty field can be discharged smoothly, try to play 2 holes, but it is difficult to ensure that both holes can hit the highest point, It is also possible to completely discharge water and air, and finally decide not to fill the borehole. It is necessary to ensure that all empty fields have filled roadways, thus ensuring that the filling rate is over 98%.
3.5.6.2 Stope dehydration
When filling, the dewatering pipeline is pre-buried, and the water tank is digbed in advance along the vein roadway. The filling dewatering flows into the water tank through the dewatering pipeline, and is discharged by the pump after being precipitated by the water tank. Part of the position is drilled into the drain hole from the lower layer, and the filling water flows directly into the ditch through the drain hole to be discharged.
4 Conclusion
After using the post-filling mining method in the Nanfeihe Iron Mine, the formation of the filling body for ground pressure management can control the collapse of the surrounding rock of the mine and the surface subsidence. In view of the technical problems in the process of filling and filling and drainage in the filling process, the technicians worked together to solve the problem effectively. The implementation of the segmented empty field post-filling mining method provides an effective guarantee for ensuring the safe operation of the underground mining of the Nanfeihe Iron Mine, and also provides a technical reference for other mines with gently inclined ore bodies.
references
[1] Burd BJ. e valuation of mine tailings effects on a benthic marine infaunal community over 29 years [J]. Marine enviro nmental research, 2002,53( 5) : 481-519.
[2] Zhang Chuanxin. Application prospects of empty field post-filling mining method in ferrous metal mines [J]. Metal Mine, 2009 (S1): 257-260.
[3] Tian Jubo, Cai Wei. Application of post-mortem filling method in Lilou Iron Mine [J]. Metal Mine, 2012 (6): 19-21.
[4] Xie Yongsheng. Sublevel subsequent filling mining method research and application of lead-zinc mine in Pakistan Du [J]. In. Nonferrous Metals Engineering, 2012(1): 39-43.
[5] Zhang Xiaopu, Guan Zaiping, Wang Huxin, et al. Monitoring and analysis of stope stability in concrete pillar post-filling method [J]. Metal Mine, 2015( 4) : 132-136.
[6] Liu Renqin, Zheng Rongxiang. Stope subsequent stage filling method and Mountain Copper Cu [J] in. Mining Technology, 2007, 7(3): 6-7.

Author: Zou Jun; Jizhong Energy Fengfeng Group Co., Ltd. in Wu'an South Ming River iron ore;
Qiu Yu; China Iron and Steel Group Maanshan Mining Research Institute Co., Ltd.; State Key Laboratory of Safety and Health of Metal Mines; National Engineering Research Center Co., Ltd.
Liu Jiadong ; Wentian College of Hohai University;
Article source: "Modern Mines": 2016.2;
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