0 Preface With increasing depth of mining life and mining, domestic and foreign press metal mine problem is getting worse, the filling process is mined-out area, one of the most effective means to control the pressure, in which the whole tailings backfill is currently at home and abroad The mine has been widely used, which can effectively control the ground pressure and reduce the environmental pollution caused by tailings discharge [1-3]. However, in practical applications, there is still a certain problem in the filling of the full tailings cement. Especially for the filling mining method, the strength of the filling body is high, and the content of some chemical components in the tailings is too high to cement the filling body. It has an important influence, which has certain constraints on the filling of many mines. In 2014, a sulfur-iron mine in Anhui Province newly established a complete tailings cement filling system. After a certain period of filling, it was found that the quality of the filling body could not meet the design requirements. For this reason, this paper studies the problems in the filling of this mine. Firstly, the chemical composition in the tailings is analyzed, followed by the filling strength test under different lime-sand ratio conditions. Finally, the influence of the chemical composition in the tailings on the strength of the filling body is discussed, so that a reasonable filling material is selected for the mine. The ratio provides technical guidance. 1 basic overview Sulfur iron mine in Anhui province is a pyrite, symbiotic iron ore deposits. The mine is currently mined by a segmented empty field and then cemented filling method. The filling process uses a full tailings cement filling process. Since the completion of the filling system in January 2014, a filling test of nearly three months has been carried out. At the initial stage of the test, the mortar concentration fluctuated greatly. It was mainly affected by the sedimentation time and the number of sand in the vertical silo. With the increase of the number of filling trials, the fluctuation of mortar concentration is getting smaller and smaller, which can be better controlled. The design requires concentration, which is gradually stable at around 62%, as shown in Figure 1. However, in the actual filling process, although the mortar concentration can meet the design requirements, the sample taken after each filling is performed on the premise that the lime sand is operated at 1:4, 1:6 and 1:8 according to the design requirements. After curing for a while in the air, most of the samples showed self-disintegration. From the filling effect of the on-site stope, after the filling of the stope for one month, there is more cracking on the surface of the filling body, and most of the cracks exceed 20mm. With the increase of time, the number of cracks is still increasing. . The quality of the filling body does not meet the design requirements. It is bound to have an impact on the two-step mining of the ore body, affecting the safety of the mine, production and recovery of mineral resources. 2 tail sand chemical content test Because the cementitious material is P. O42.5 cement has no deterioration or hardening. In order to understand the cause of the deterioration of the filling quality, the chemical composition of the whole tailings needs to be measured to understand whether it contains chemical components that affect the filling effect. . The chemical composition test results of tailings are shown in Table 1. From the results of the measurement in Table 1, it can be seen that the content of S in the tailings is as high as 8.82%, which is far more than 1% to 3%, and the content of CaSO4 is also 4.07%. According to the experience of mines using cementation filling method at home and abroad and the research results of research institutes, it is known that some chemical components in the filling materials and their contents are too high, which will have certain influence on the physical properties of the filling body [ 4-5]. The main chemical components in the tailings that have a great influence on the strength of the filling body are Fe, FeS2, MgO, S, SiO2, Al2O3, CaO and CaSO4. In comparison, the S content has a significant effect on the late strength of the backfill, mainly because the S-containing minerals (mainly pyrite-based sulfide minerals) act in the air and water, and the sulfide minerals are oxidized and formed. SO42-, when the concentration reaches 1500 ~ 10000g / L, the gypsum can form insoluble aluminum salts and sulfur crystals have a damaging effect on cement or other cementitious material. The failure mechanism is mainly due to the formation of sulphoaluminate crystals and dihydrate gypsum, the volume expansion of which is more than twice the internal stress generated in the filling body, thereby destroying the filling body. Domestic tests and production practices have proven that most of the oxidized high-S-tail sand test blocks disintegrate on their own, whether in air curing or water conservation. It is generally believed that the tailings contain S in excess of 1% to 3%, which may have a detrimental effect on the late strength. When the tailings contain oxidized S compounds, the harmful effects are more pronounced [6-7]. Therefore, the presence of S and its oxides in the tailings of this mine has an important influence on the gelation effect of the cemented backfill, thus affecting the quality of the backfill. 3 filling body strength test In order to further determine the effect of chemical composition such as S on the quality of the filling body, the uniaxial compressive strength test was carried out on the filling block under different lime sand ratio conditions. The actual filling of the mine is based on the ratio of 1:4, 1:6 and 1:8. The bottom layer is filled with 1:4 lime sand ratio, and the ratio is 1:6 and 1 in order. : 8 gray sand ratio. In order to simulate the on-site filling situation, the sand-sand ratio used in this test pack is consistent with the actual lime-sand ratio. According to the actual filling slurry concentration and design requirements at the site, the test pieces with a ratio of 1:4, 1:6 and 1:8 were prepared with slurry concentrations of 64% and 66%, respectively, and 6 test blocks were produced for each group. The uniaxial compressive strength test was carried out after 3, 7, 28, and 60 days of curing. The filling body strength tester adopts WYA-2000 electro-hydraulic pressure testing machine. The test block size is 70.7mm×70.7mm×70.7mm. The pressure of the test block is shown in Figure 2. 4 test results analysis The average uniaxial compressive strength of the test blocks at different ages is shown in Table 2. The uniaxial compressive strength variation curve of the packed body test block is shown in Figures 3 and 4. It can be seen from Fig. 3 and Fig. 4 that the test piece with a slurry concentration of 64%, a lime-sand ratio of 1:4, and a slurry concentration of 66% and a lime-sand ratio of 1:6 reach the highest strength at 28d, and the rest is 7d. Achieve the highest intensity. Among the test pieces with a concentration of 66%, the 60d strength ratio of the sand-cement ratio of 1:4 is 0.785MPa lower than the highest strength, which is 49% lower; the 60d intensity of 1:6 is 0.592MPa lower than the highest strength, which is 39.3%. The 1:10 60d intensity is 0.514 MPa lower than the highest strength, a 52% decrease. For the test piece with a concentration of 64%, the 60d strength ratio of the 1:34 is lower than the highest strength of 0.583MPa, which is decreased by 37%; the 60d intensity of 1:6 is 0.383MPa lower than the highest strength, which is decreased by 43.4%; The 60d intensity of 1:8 is 0.326 MPa lower than the highest strength, which is a decrease of 41.6%. It can be seen that the same slurry concentration, different lime-sand ratio, the strength of the filling block after the highest value in the 28d curing age, a significant drop, the strength of the 60d curing age is about 50%. From the plot of the test block strength variation curve, the higher the slurry concentration, the greater the strength of the filling body, the larger the sand-sand ratio, the greater the strength of the filling body, and the 60d strength of the filling body is higher than 0.45 MPa. The strength of most of the filling blocks has been greatly reduced after 28 days of curing. However, when the strength drops to about 0.45 MPa, the tendency to decrease becomes extremely slow and tends to be stable. It indicates that the influence of S and its oxides in the tailings on the strength of the filling body is limited. As long as the content is reduced, the strength of the filling body can be effectively improved. 5 Conclusion Through the test of the chemical composition in the tailings and the uniaxial compressive strength test of the filling body, it is found that the S content in the tailings is as high as 8.82% and contains 4.07% of CaSO4, which seriously affects the gelation effect of the filling body. As a result, the filling body has a sharp drop after reaching the highest strength, and the 60d strength is reduced by about 50% compared with the highest strength. It can be seen that the quality of the full tailings cemented backfill in Anwei's pyrite mine is greatly affected by the S and its oxides in the tailings. It is necessary to extract the S and its oxides from the tailings to reduce its content. In order to ensure that the late strength of the filling body meets the production requirements. references: [1] Song Weidong, Li Haofeng, Lei Yuankun, et al. Experimental study on the cementation performance of the full tailings of Chengchao Iron Mine [J]. Mining Research and Development, 2012, 32(1): 8-11. [2] Yilmaz E, Belem T, Bussière B, et al. Curing time effect on co nsolidation behaviour of cemented paste backfill co ntaining different cement types and contents [J]. Co nstruction and Building Materials, 2015, 75: 99 - 111. [3] Chen Du, Qiao Dengpan, Zhang Guolong, et al. Analysis of modern mine filling and mining method [J]. Mining and Metallurgy, 2013, 22 (3): 30-35. [4] Wang Bao, Zhang Huyuan, Dong Xingling, et al. The effect of sulfide oxidation on the long-term strength of the filling [J]. Chemical Minerals and Processing, 2007 (10): 29-31. [5] Xu Weihai. Study on the influence of sulfide on the quality of backfill in tailings [J]. Mining Research and Development, 2009, 29(5): 4-6. [6] Sun Henghu, topaz Cheng, Yang Baogui. Contemporary cement filling technology [M]. Beijing: Metallurgical Industry Press, 2002. [7] Liu Tongyou. Filling mining technology and application [M]. Beijing: Metallurgical Industry Press, 2001. Huang Mingqing; Beijing Jinchengg Mining Technology Research Institute Co., Ltd., Beijing 101500, China; School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China; Wu Aixiang;School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China; Guillotine Machine,Automatic Guillotine Machine,Hydraulic Cnc Guillotine Shears,Hydraulic Cnc Press Brake WEISS MACHINERY CO., LTD. , https://www.weissmachinery.com
Author: Tan Wei; Beijing gold mine integrity Technology Research Institute Co., Ltd., Beijing 101500;
Source: Mining Technology 2015, 15(5);
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