The Heshan Iron Deposit is a high-temperature gas-liquid metasomatism (stratigraphic) deposit, which mainly occurs in the contact zone between the diorite and the Zhouchong Village Formation and the Zhouchong Village limestone near the contact zone. The ore body strikes 320, the strike length is 550m, the maximum extension depth along the trend is 960m, the average thickness is 23m, and the ore body inclination angle is about 45. The ore is dominated by semi-artificial hematite and a small amount of magnetite. The ore is mainly loose and powdery, soft and unstable, and a small amount of hard. The main rocks of the top and bottom of the ore body are limestone, marl , sandstone and shale , which are generally hard and complete. The bottom plate is mainly limestone, marble , diorite, and has good stability. The local near-rock surrounding rock is altered diorite and has poor stability. (1) Section height. According to the shape of the ore body and the thickness of the ore body, it is determined that the height of the section above the level of -150m is 10m, and the height of the section below the level of -150m is 12.5m; when the thickness of the ore body is greater than 12m, the approach is arranged vertically, when the thickness of the ore body is less than At 12m, the approach is arranged along the strike. Heshan Mountain adopts low-poor ore-mining method. Therefore, when the section height H=12.5m, the approach spacing is S=12m; when the section height H=10m, the approach spacing is S=10m. In recent years, a large number of experimental studies and practical applications have proved that the new high-efficiency mining method is suitable for the mining technical conditions of the Heshan Iron Mine and at the same time provides experience for the mining of such ore bodies. At present, while the production site has reached the design production capacity, it also exposed some problems that still need to be solved.
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1 mining plan
The dip angle of the ore body of the Heshan Iron Deposit is about 45. The ore body and the surrounding rock joints are developed with poor stability. Especially the ore is mainly loose and powdery, and the exposed area is small. Such ore bodies are suitable for mining methods that have no bottom structure, have a small degree of cutting of the ore body, and are dispersed and mined. For this reason, a sublevel caving method without a bottom column was selected. Due to the softness of the ore rock, it is difficult to mine, support and recover the mining roadway. Therefore, only by reducing the mining coefficient can the mining efficiency be improved.
However, due to the gentle inclination of the ore body, if the mining coefficient is reduced by increasing the structural parameters of the stope, the ore loss will be increased. In order to achieve the purpose of reducing the mining coefficient without reducing the ore recovery rate, sufficient mining engineering is arranged on the lower disc side, and at the same time, the mining project on the upper disc side is greatly reduced, and the recovery space of the lower disc side mining project is utilized. The ore body on the upper plate side is induced to naturally fall. Based on this idea, the technical solution using induced caving is determined (see Figure 1). At the same time, according to the principle of combining the induced caving technique with the sublevel caving method without pillars and the research results of the continuous caving area of ​​the rock mass, the scheme of simultaneous mining of the upper and lower working faces was adopted (see Figure 2). That is to say, the -50m and -150m sections are used as the first mining section, and the space provided by the -50m and -150m section mining induces the natural mining of the upper ore body, and is also the lower ore body (the middle section of -100m and the level below -150m) The mining is carried out to relieve pressure. 
2 new high-efficiency mining method process parameters
2.1 Determination of the structure parameters of the stope
According to the similarity ratio of 1/100, the flow parameters of the ore body in the Heshan mining area were experimentally determined, and then the structural parameters of the stope were determined based on the ore flow characteristics and ore body conditions.
(2) Route spacing. The calculation formula of the route spacing is:
2.2 Determination of the parameters of the recovery route
Due to the sub-column sublevel caving method, when the last section of the ore body is recovered, a large ore ridge residue is formed in the lower part of the goaf. Considering the utilization and economic value of the ore resources, this part of the ore should be recovered. Therefore, a recovery route is set in the surrounding rock below the residual body (see Figure 3). According to the experience of similar mines in China and the use of cut-off grades, it is determined that the recovery route will be excavated at the 6~7m position of the surrounding rock. The distance between the recovery routes is 12.5m.
3 conclusions and existing problems
(1) Due to the poor stability of the ore body, the induction of caving will form a large caving area, and whether the mining of the upper working surface will cause safety hazards remains to be studied. A systematic monitoring system should be established to monitor the relationship between the sinking of the roadway floor and the time, the signs before the rock body falls, and the falling edge of the empty side wall and the surrounding rock.
(2) From the actual situation of the site, the situation of induced and falling is different, the irregularity of the ore body is not irregular, and it does not fall in the shape of the ellipsoid expected, and it produces a large number of large parts. There was a wave of surrounding rock falling on the upper plate, which was detrimental to ore recovery.
(3) Due to the poor stability of the center of the ore body, the caving property is good, and the stability of the ore at both ends is good, it is difficult to form a caving condition. Therefore, in the future, the recovery of this part of the ore body must be increased by technical research and investment. A reasonable, safe and feasible recovery plan.
references:
[1] Ren Fengyu. Research on stope structure and ore-mining method of sublevel caving without foundation column[J].China Mining,1995,(6).
[2] weeks were red, Renfeng Yu. Xiadian application of gold ore lean low loss in sublevel caving [J]. Mining Industry, 2006, (1).
Article source: Mining Technology; 2008.8 (6)
Author: Huangxiao Zhong, Liu Faping; Gushan Mining Co., Ltd., Anhui when the float County  243184
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