Research On The Key Teclmiques Of Mining Method Changed From Caving Method To Filling Method In Ying-fang Silver-lead-zinc Mine

The ore bodies at Yin Fang silver-lead-zinc mine are located in the fractured zone, F1. So, the engineering geological conditions characterized by fractured ore bodies and surrounding rocks and the poor stability are complex. At present, the sublevel caving method which is featured by high loss and dilution rates is applied. Furthermore, the technical and safety problems, such as the ground subsidence, in the mining process will restrain the development and affect the economic benefits of the mine. Based on preliminary analysis, filling method rather than caving method will be applied in further mining activities. While in the transition process of mining methods, the isolation layer between caving and filling mining areas should be preserved. Therefore, to improve the economic benefits and ensure the safe transition of mining methods, investigations on the selection of mining methods and the stability of isolation layer should be conducted. The main works conducted in present thesis are listed as follows:(1) First, mining technical conditions include the engineering geology, hydrology and characteristics of ore bodies were investigated. Based on present mining conditions, the complex technical problems were analyzed systematically.(2) Four kinds of mining methods were preliminarily proposed based on the technical mining conditions featured by fractured and instable ore bodies and surrounding rocks. The comprehensive evaluation method, AHP-Fuzzy, was applied in the analysis on technical economy, advantages and shortcomings of these mining methods. And the upward stoping drift and cemented filling mining was determined as the suitable one.(3) The widths and the heights of the drifts were optimized by numerical simulations which were divided into 16 groups with varying structural parameters. According to stresses, displacements and plastic zones distributions of ore bodies and the surrounding rocks, the optimized drift height and width were 5 m and 4 m respectively.(4) According to present mining conditions, the location of the isolation layer was determined. 6 theories were applied in the calculation of the isolation layer thickness, and the safety factors of the isolation layers with varying thickness were obtained by applying the limit equilibrium method. The relationship between the safety factor and the isolation layer thickness was also proposed. When the safety factor equals to 1.5, the thickness is 10 m.(5) To analyze the stability of the isolation layer in the transition period, the 3D numerical model was established using the software, Midas/GTS. Based on the simulation software, Flac3 D, the corresponding mining activities were simulated. Results indicated that great subsidence was caused by the great disturbances of stress when caving mining method was used at early mining stages. As the mining activities proceeded, the deformation and the tensile stress in the isolation layer would increase, and tensile failures and the connection of plastic zones were observed in the isolation layer. After the transition mining period, a new stress equilibrium state was achieved, and the final deformation of the stable isolation layer was limited. To prevent isolation layer from local fallings, corresponding supporting measures should be conducted.