| Jinchuan nickel mine is China’s largest, the world’s third largest copper sulfide nickel deposit. Its ore body rock is broken, with high crustal stress, buried deep and thick, so it is a large-scale deposit that has difficulty to be mined. In order to achieve ore body safety and efficient mining, downward tennel cemented filling method is adopted, rod-mill tailings are used as filling aggregate and cements are used as the binding material. Filling material costs as high as 147 Yuan/m3, which is quite rare in both domestic and abroad. Due to the fact that international nickel price has been slumping in recent years, so the economic benefits of Jinchuan mining was brought with great pressure. In this paper, it conducts research on mining technologies to reduce the cost of filling mining.Firstly, this paper carries out physicochemical properties analysis on available waste resources in Jinchuan Mine. On this basis, the exploratory experiment of phosphogypsum-based cementitious material based on high activity slag of Tangshan Iron and Steel is conducted. Then, according to the low activity slag of JiuSteel, the strength test of cements filling with different slurry concentration and different powder fineness is carried out. In this way, the early strength of cementitious filling material of phosphogypsum-based cementitious material can be improved through tests of different admixtures. In addition, in order to realize the utilization of solid wastes, particle size grading analysis and optimization of mixed aggregates are carried out on the basis of single grain size analysis. After testing the strength of mixed cementitious filling material and the rheological properties of the filling slurry,’it determines the ratio optimization of mixed filling aggregate to meet the filling mining of Jinchuan, the optimum design parameters of the filling slurry are also obtained. Finally, according to the optimized design of the filling slurry, and filling system of the Longshou mine in Jinchuan Mine, it conducts numerical simulation of self-flow transport characteristics of high concentration slurry, which can provide the theoretical basis for the application of the mixed coarse aggregate of phosphogypsum cementitious material in Jinchuan Mine Industrialization. Through the study, the main conclusions of this study are as follows:(1) Optimized formula of phosphogypsum-based cementitious materials with different compositions is obtained based on high activity slag of Tangshan Iron and Steel: ①The best formula of lime-mirabilite activators in two groups are as follows: lime:6%～7%, ardealite:30% and mirabilite:3%. ② formula of lime-NaOH in two groups are as follows:quicklime 4%-6%, gypsum:30% and NaOH:2%. ③The best formula of lime-NaOH- mirabilite activators in three groups are:lime 5%, phosphogypsum 30% and NaOH 3%, mirabilite 2%. The strength of mixed aggregate filling of activator phosphogypsum-based cementitious material at 3d,7d and 28d reached 1.91MPa,8.99MPa and 12.88MPa, respectively, which satisfied the requirements of cementing and filling mining in Jinchuan Mine.(2) The change law of optimum formula of the phosphogypsum-based gypsum-based agglomerates is revealed:the maximum dosage of phosphogypsum is 40%, and the minimum dosage of slag powder was 50%. With the increase of mirabilite’s dosage, the early strength of cementation filling body will be increased and the later strength will be decreased, and the dosage of mirabilite should be less than 2%. With the increase of lime dosage, the strength of cemented filling body at 3d and 28d decreases accordingly, and the decrease rate is closely related to the dosage of mirabilite. Decreased rate of strength at 3d decreases along with the increase of mirabilite’s dosage, at 28d, the strength is on the contrary. With the increase of lime dosage, the strength of cemented filling body also increases at 7d, and its increase rate decreases along with the increase of mirabilite’s dosage.(3) The optimal formulation of phosphogypsum-based cementitious material based on JiuSteel low-activity slag is:5.5%～6.0% of lime,30%～33% of phosphogypsum, 1.5%～2.0% of NaOH and 2.5%%～3% of mirabilite. The average particle size of cementitious material should be less than-16μm, early strength agent or synergist need to add to improve the early strength of cementitious materials. When the cement-sand ratio is 1:4 and the slurry concentration is 80%, the strength of the waste aggregate coarse cemented fillings meet the design strength of cemented filling body of Jinchuan mine.(4) The mechanics characteristics law of phosphogypsum-based cementitious material of JiuSteel slag is revealed. The hydration of phosphogypsum-based cementitious material is slow at 3d, and the strength increases rapidly at 7d, and the early strength increases with the increase of slurry concentration. When the concentration of filling slurry increased by 1%, the strength of phosphogypsum-based cementitious material filling body increased by 0.09MPa and the strength increased by 0.6MPa at 7d.(5) The early strength of phosphogypsum-based cementitious filling material increases along with the increase of fineness of cementitious material. Under the circumstance that the average particle size of cementitious material is greater than 16μm, the early strength of cementitious filling material increases linearly with the increase of fineness. But when the average particle size of powder is less than 16μm, the strength of cementitious filling body expands exponentially. Therefore, it can be confirmed that the average particle size of the phosphogypsum-based cementitious material should be-16um, and the content of +45μm particles should be less than 8%.(6) Under the circumstance that the mixing ratio of waste rock and rod is 3:7, the cement-sand ratio is 1:4 and the concentration of slurry is 80%, the rheological curve of the mixed filling slurry is a convex curve which does not pass the origin, showing a nonlinear crossover relationship. The rheological curve is convex to the shear stress axis and can be characterized by the H-B rheological model. Thus, the initial yield stress of the slurry is 51.66Pa, the viscosity coefficient is 4.53Pa · s, and the Reynolds number Re is in the range of 37.74～246.56. Moreover, as Re is far less than 2100, so all the filling slurry manifests the laminar flow state in the pipeline transport. |
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