| Jinchuan nickel mine is one of three resources comprehensive utilization bases in China; it is also the largest nickel, cobalt and other non-ferrous metals production base in China. At present, 85% of nickel and 50% of cobalt are produced by Jinchuan nickel mine. Because the mining conditions of Jinchuan ore body are very bad due to the high-stress area, very deep-lying and poor rock mass, the stability of backfill of underhand cut-and-fill drift stoping and the ground control of whole mining area are always the difficult problems faced by Jinchuan nickel mine.Based on the reliability theory and No.2 mine area of Jinchuan nickel mine, in combination with in-situ monitoring, engineering geological investigation, theory analysis, numerical simulations and similar materials simulating tests, the author systemically study the stability of backfill in a single drift mined by underhand cut-and-filling drift stoping, then he firstly studies the mining sequence of a single panel, the drift-layout method between upper slice and lower slice in a panel, and the mining sequence of whole No.1 ore body. Two important problems, i.e. the mining stability of horizontal pillar and the effect of the 16th-line vertical pillar on the ground control of whole mining area in No.2 mine area, are systematically studied.In this paper, the reliability theory is applied for the first time to study the stability of loaded layer of drift, the mechanical model of loaded layer is established, the stress distribution law of loaded layer is analyzed, a new conception is put forward to evaluate the backfill stability by use of the reliability index of stability of loaded layer based on the deep study on the failure mechanism of loaded layer. Based on the reliability theory, an evaluation method of the stability of backfill of underhand drift is established. The intrinsic relation among the thickness and strength of loaded layer, the applied load on loaded layer and the width of drift is revealed. The specific engineering measures are presented to improve the stability of backfill.The mutual relation among the thickness and strength of loaded layer, the width of drift, the stability of loaded layer and the cost of backfill is researched. Based on the reliability theory, the backfill techno-economic analysis method is provided. Based on the reliability index at 90% of the loaded layer stability, the relation formula among the backfill cost and the width of the drift, the thickness and strength of loaded layer is established.The traditional method for determining the strength of the backfill in underhand drift cut-and-fill stoping is broken through, and a new method of determining the strength of backfill, based on the reliability theory, is put forward. The backfill strength determining method is perfected. The method is used for the rock-cemented fill mining technology in Jinchuan No.2 mine area.According to the results from analyzing the main control factors of loaded layer unstability of underhand drifts, in combination with the in-situ situation of mechanized mining panel at Jinchuan No.2 mine area, an optimal mining sequence of a panel is put forward. The FLAC3D numerical simulation analysis is used to study the layout pattern between the upper andlower drifts. It is concluded that intersecting the drifts between the upper slice and the lower slice is more beneficial to stress distribution in the backfill, and controlling the movement of backfill and the surrounding rock.The FLAC2D numerical simulation analysis and the large-scale similar material simulating test are used to research the six kinds of feasible mining sequence of 1# ore body in No.2 mine area. The results shown that the optimal mining sequence of l# ore body in No.2 mine area is from its one end gradually to the other. Based on the conclusions drawn from the numerical simulation analysis and the similar material simulating test, some specific recommendations on adjusting 10th and 11th five-year production scheduling plan, and the mining sequence of Level 850m ore body in the future are made.Combined with the numerical simulation and the large-scale similar material simulating test as well as the in-situ geological engineering survey, the stability of horizontal pillar in the thick ore body mined by multiple levels in Jinchuan No.2 mine area is researched. The dynamic ground stress distribution law of the horizontal pillar, the backfill and the surrounding rock during the whole mining process is discovered. The conclusions show that the horizontal pillar will not instabilize suddenly during the mining process. According to the ground stress characteristics of the horizontal pillar, the specific engineering measures are provided for mining the horizontal pillar in the future.Combined with the analyses method of catastrophe theory and the mechanics model of the horizontal pillar, a CUSP catastrophe model of horizontal pillar is established, the instabilizing criteria of sufficient and necessary mechanical condition of horizontal pillar are derived, and the balance state of pillar is discussed. The research method of the CUSP catastrophe model of horizontal pillar instability based on reliability theory is put forward, and a new idea on the application research of the catastrophe theory is presented.The FLAC2D numerical simulation, the in-situ monitoring and the mechanics analyses are used to evaluate the ground stress control effect of vertical pillar at the 16th line. It is concluded that retaining the vertical pillar at the 16th line plays a important role in the stability of backfill in whole mining area. Also, it is beneficial to the protection of main underground constructions, especially to the west main shaft.Through the study of this paper, backfill mechanics theory is enhanced, and the theory related to underhand cut-and-fill drift stoping method is enriched. The results of this paper provide scientific direction for the dynamic ground stress control of Jinchuan No.2 mine area and similar mines, it is of theoretical significance and engineering application values to the safe, economical, and reasonable mining of the underground mineral resources.
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