Abstract: Based on the geological conditions and ore-rock physical properties of a gold mine in Inner Mongolia, the numerical simulation research of granule flowing laws of the steeply inclined and narrow veins is analyzed by using discrete element method of the particle flow. The results of the analysis show that the flow patterns of particle can be divided into side wall control zone, transition zone and free fall zone. The patterns of stress transmission can be divided into homogeneous stress zone, decompression and unstable arches. Based on what is mentioned above, the author analyzes the effect of the changes of ore friction angle on ore drawing process, especially the effect on the size of dilution triangle ore body and contact force between particles in ore drawing process. The results of the analysis are as follows: 1) The greater the ratio of the friction angle δ and the friction angle φ of ore is, the bigger the dilution triangle ore body will be; 2) The greater the friction angle of particles is, the more frequent the production and collapse of the unstable arches will be and the easier to produce stable arch. Based on the research results, a method of optimizing the mining structural parameters and reducing the ore loss and dilution is put forward.

Key words: sublevel caving method, particle flow method(PFM), friction coefficient, steeply dipping thin orebody