In order to improve the production capacity of the stope and reduce the mining cost, the mine is generally divided into two steps, that is, the mining column after the mining room. The one-stage mining room is made of original rock on both sides, with large production capacity and safe working environment. The two-step pillar is affected by factors such as concentrated stress in the stope, blasting vibration damage, ore body integrity and strength reduction, which increases the difficulty of mining. At the same time, two-step mining
The sides of the field are filled with strength, which is much lower than the strength of the original rock, which greatly reduces the stability of the mining of the two-step pillar and seriously threatens the safety of the work in the stope [2]. Therefore, the mining environment of the two-step pillar and the one-step mine is quite different, and the structural parameters of the stope should be separately analyzed for better, so as to ensure the safe and efficient mining of the two-step pillar.
1 engineering background
Luo River iron ore is a large underground mine, ore bodies are bedded, gentle lenticular [3]. The ore body is buried at -382～-846m, the inclination angle is 3°～12°, the east is shallow and the west is deep, the shallowest is 425m from the surface, and the deepest is 856m. The west edge of the deposit is affected by the F001 fault and the depth is 910m. There are 8 iron ore bodies, of which I# and II# are the main ore bodies. The ore body is thick, the spatial shape is complex, the mining area is wide, and the regional fault structure is developed.
Luo River iron ore complex surface facilities, there are villages, roads, rivers and ponds, farmland, on the eastern side Hefei to Tongling mining area highways, such as rivers and ponds north, middle Quaternary surface thickness, is rich in water times above the ore body Quartzite rock mass, local area has anhydrite ore [3]. Therefore, according to the occurrence conditions of each section ore body, most of the ore bodies in the north of the II longitudinal exploration line are suitable for the vertical deep hole stage empty field post-filling mining method, and the corner part adopts the point-column stratified filling method or medium depth. The hole segmentation empty field is filled with mining method; the south of the II longitudinal exploration line is suitable for medium-deep hole segmentation empty field and post-filling mining method, and the corner portion adopts point-column stratified filling method. In this paper, the structural parameters of the two-step stope in the deep-hole section of the ore body in the south of the II longitudinal exploration line are optimized.
2 two-step stope parameter optimization numerical simulation
2.1 Rock mechanics parameters
The main body forming paste magnetite present limestone and alkali feldspar rock. Mine development rock mainly tuffaceous siltstone, trachyandesite, tuff, secondary quartz rock, hard gypsum ore, limestone paste, alkaline lithofeldspathic, altered trachyandesite and fine cuttings re breccia Wait. The rock mass in the upper part of the ore body changes greatly, the rock block strength is high, the crack develops, and the local is affected by kaolin and chlorite, which makes the rock structure soft and the strength is reduced. The bottom of the ore body is generally dense and hard alkaline feldspar rock, plaster limestone, the crack is not developed, and the core is intact. Through the engineering geological survey of the rock mass in the mining area, the sampling test of the upper and lower rocks and the strength test of the filling body, the mechanical parameters of the rock mass and the filling body in the mining area are obtained (Table 1).
2.2 Stope structure parameter simulation scheme
By analyzing and comparing the relevant mine experience of using the upward approach filling mining method in China and referring to the current actual situation of Luohe iron ore mining, the stope field selection is 20m wide and the stope height is 15m.
In order to determine the reasonable structural parameters of the two-step mining site, according to the mining characteristics of the Luohe Iron Mine sub-fill mining method and the stability of the one-step mining, the two-step mining yard is 16, 18, 20 m wide. The specific simulation scheme is shown in Table 2.
2.3 Calculation model establishment
Referring to the structural parameters of the existing stope, consider 4 to 5 times the diameter of the excavation as its affected area, that is, the surrounding rock range of the stope. Therefore, the model is divided into four parts, namely the overlying load on the stope, the one-step stope body, the stope body and the stope floor. The calculation model is shown in Fig. 1.
2.4 Analysis of numerical calculation results
The research shows that there are two kinds of failure modes in the top of the two-step mining site [4]: ​​one is that the upper load is large and the large deformation and damage occur; the other is that the tensile stress of the roof exceeds its own ultimate tensile strength after mining. Stretched and destroyed. This paper mainly analyzes the displacement and stress changes of the roof in the two-step mining process with different spans, so as to optimize the parameters of the stope.
2.4.1 Stress Analysis
The stress cloud diagram of the two-step stope roof with different spans is shown in Fig. 2. It can be seen that when the span of the stope is 16m, the maximum tensile stress appears in the middle part of the roof of the stope, and its distribution area is less. When the span of the stope is 18m, the maximum tensile stress zone appears in the roof of the stope, and its distribution area It accounts for 30% of the roof of the stope. When the span of the stope is 20m, the maximum tensile stress area of ​​the roof of the stope is very obvious, and its distribution area accounts for 90% of the roof of the stope. The rock of the roof of the stope will be tensileally damaged. The roof collapses or falls, posing a serious threat to the safety of the site.
The change of roof stress during the excavation of two-step stope with different spans is shown in Fig. 3. It can be seen that with the gradual increase of the span of the two-step stope, the maximum tensile stress of the roof increases gradually, and the rate of change of the maximum tensile stress of the roof gradually increases. When the width of the stope changes from 16m to 18m, the increase is 0. .11MPa/m; when the width of the stope is changed from 18m to 20m, the increase is 0.23MPa/m; when the span of the stope is 20m, the maximum tensile stress of the roof of the stope is 2.61MPa, which exceeds the limit of the roof. Strength, the roof is prone to tensile damage and threatens the safety of the stope.
2.4.2 Displacement analysis
The displacement map of the top plate of the two-step stope with different spans is shown in Fig. 4. It can be seen that when the span of the stope is 16m, the maximum displacement in the middle of the roof is 20mm, and the distribution area is less in the roof of the stope. When the span of the stope is 18m, the maximum displacement of the roof is 28mm, and the distribution area covers the roof of the stope. When the span of the stope is 20m, the maximum displacement of the roof is 40mm, and the distribution area accounts for 1.8 times of the width of the stope. The roof and surrounding rock of the stope are deformed, and the rock is easy to detach and the roof collapses. Falling tops pose a threat to the safe production of the stope. At the same time, there is a relatively obvious bottom drum at the bottom of the stope, but the displacement of the bottom drum is small, which has little impact on production safety.
The variation of the displacement of the roof during the excavation of the two-step stope with different spans is shown in Fig. 5. It can be seen that with the gradual increase of the span of the two-step stope, the maximum displacement of the top plate is gradually increased, and the rate of change of the displacement of the roof is gradually increased. When the width of the stope is changed from 16m to 18m, the displacement of the roof is increased by 4mm. /m; When the width of the stope is changed from 18m to 20m, the displacement of the roof is increased by 6mm/m; when the span of the stop is 20m, the maximum displacement of the roof of the stop is 40mm. According to the actual experience of mining at home and abroad [5], when the width of the stope is large, the displacement of the roof of the stope is close to or exceeds 50mm, and its own stability is poor.
3 conclusions
(1) According to the results of stress analysis, the tensile stress and its change rate of the top plate of the two-step stop are gradually increasing, and when the span of the two-step stop is 20m, the maximum tensile stress of the roof is 2.61 MPa, which is beyond its own. The ultimate tensile strength, and its distribution area accounts for 90% of the roof of the stope. The roof is prone to tensile failure and the safety of the stope is poor.
(2) From the results of displacement analysis, it can be seen that the displacement and the rate of change of the top plate of the two-step stop are gradually increasing. When the span of the two-step stop is 20m, the maximum displacement of the roof is 40mm. According to the actual experience of the project, The roof of the stope is prone to local upswing and poor self-stability.
(3) Considering the mining production capacity and safety requirements of the mine, it is recommended that the two-step stop has a span of 18m and a height of 15m.
references
[1] Goodman, Li Xibing. Modern metal deposit mining science and technology [M]. Beijing: Metallurgical Industry Press, 2006.
[2] Liu Zhiyi, Hou Jinliang, Zhao Guoyan, et al. Stability analysis and engineering application of surrounding rock on the second step stop[J]. Metal Mine, 2015 (11): 143-148.
[3] Wang Lingsong. Study on optimization method of mining method for rich water and thick ore body in Luohe Iron Mine [D]. Changsha: Central South University, 2014.
[4] Liu Zhiyi, Zhang Lichun, Zhao Guoyan, et al. Structural parameter optimization and engineering application of two-step stope based on FLAC3D [J]. Metal Mine, 2015(10): 6-10.
[5] Zhou Bihui. Research on low-depletion underground mining of high quality gypsum mine in Hanyuan, Sichuan [D]. Changsha: Central South University, 2014.
Author: Jia Wei, Xiaowen; Anhui Masteel Luo River Mining Limited Liability Company;
Article source: "Modern Mines"; 2016.4;
Copyright:
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