Study On Reasonable Cut-off Grade For Ore Drawing In Sublevel Caving Method

Firstly, the technology status quo on cut-off grade for ore drawing before the paper, especially, extreme cut-off grade of ore drawing, combination cut-off grade of ore drawing, and undilution cut-off grade of ore drawing, are analyzed and commented; the related theories on cut-off grade for ore drawing including relax medium, continuous medium theory of ore drawing, and so on; are analyzed; and, fallen ore and rock's movement law under the covering of fallen wall rock when different cut-off grades of ore drawing are adopted is discussed.Later on, through combining theory with experiment, essential internal relation and mutual transform among different cut-off grades of ore drawing are discussed and expounded for the first time, and some new viewpoints are put forward as follows:(1) Although different cut-off grades of ore drawing and corresponding ore drawing are based on different theoretical basis, but all radically rely on ellipsoid theory of ore drawing and are affected by the theory with its advantage and localization, and there are still internal essential relations among them, that is, extreme cut-off grade ore drawing and undilution cut-off grade ore drawing are one special kind of combination cut-off grade ore drawing, but have respective characteristics, applying conditions and will lead to different economic effect, and so on.(2) Combination cut-off grade ore drawing is the most complicated, it includes all cut-off grades ore drawing, but not each is the best, undilution cut-off grade ore drawing is the most perfect ore drawing but is very difficult to carry out large-scale industry produce because of the limitations such as mine body obliquity and thickness, strict ore drawing management, and so on, so, It is better,, to adopt suitable combination cut-off grade ore drawing, for example, reduce dilution rate step by step.(3) Different cut-off grades ore drawing are put forward according to different maximal total profit, different using degree of flow space continuity of fallen ore and rock, different relation between loss and dilution, different using degree of ore remained mass, and so on, so, them seems to be different professedly.And the factors need to be considered, possible problems need to be faced, necessary suggestions and measurements, and so on, are put forward from more extensive meaning.At last, the problem on the occurrence of the random number in computer random simulation is analyzed, language VB 6.0 is selected as programming language, on the basis of nine-block random simulation model for ore drawing, computer flow chart of ore drawing in sublevel caving method is designed and the program on random simulation is programmed and empoldered, and the problem on the production of random number and how to distinguish down-floating module are better solved. The feasibility of nine-block random simulation ore drawing is validated primarily. At the same time, both the expansion and visualization of the program are improved.