Research of the isolated extraction zone form and determination of optimal independent advance under different end wall angles

In order to analyze the form of the isolated extraction zone (IEZ) in side drawing and get optimal independent advance with large structural parameters, drawing models with the mesomechanical properties of ore granular media were constructed based on the particle flow theory and PFC3D code. The reliability of the drawing models was validated by comparative analysis between existing research conclusions and simulated results. On this basis, a study on independent advance of side drawing at different end wall angles in the structural parameters of 18 m×20 m was performed. The results show that the IEZ form is incomplete and is not a regular ellipsoid at different end wall angles. When the drawn mass is equal, the IEZ height increases with decreasing end wall angle and the IEZ form becomes more and more slender. The trend of the IEZ height at both the infinite boundary condition and the boundary condition of different end wall angles can be divided into two stages:in the first stage, the IEZ height rapidly increases in the exponential form at the initiation of side drawing and its growth rate decreases with the increasing of drawn mass, while in the second stage the IEZ height linearly increases with the increasing of drawn mass. It is suggested that the end wall angle of 85°-90° and the independent advance of 4. 8 m should be used in the structural parameters of 18 m×20 m.