Numerical modeling of the draw behavior of large-scale physical models of the block-cave mining method

Barker, K. A. ; McNearny, R. L.
Organization: Society for Mining, Metallurgy & Exploration
Pages: 7
Publication Date: Jan 1, 2000
Four numerical models written with the "PFC2D " program were compared against four similar physical models. The numerical models were constrained numerically to closely follow the caving behavior of the physical models. Results from the numerical analyses closely simulated both the granular and blocky behaviors of the physical models, including bridging and interlocking of the simulated orebody during draw. The drawdown patterns and the rate of draw developed during numerical modeling also closely simulated the physical models. The same assumptions and governing parameters used in analyzing the first four models were applied to an additional model. The fifth model employed a completely different, uneven, draw sequence than the other four models, allowing the material to flow in a more granular manner with a demonstrated instability of the undercut sections between each drawpoint opening. Drawdown patterns and behavior of the numerical material of the first four models progressed at uneven and inconsistent rates, similar to those seen in the physical models. By inspection, the overall shape and flow lines of both the numerical and physical models were close in the area removed and in the flow characteristics. The fifth model proved to be the most unstable of all the models tested, with poor correlation to the physical models. The uneven draw sequence, coupled with an additional frictionless wall condition and an added drawpoint, caused the material to flow in a very granular manner. Information generated by this study can be used as a first approach in determining the proper draw rate, drawpoint spacing and undercut thickness for a block-caving operation. Numerical models are often difficult to predict and interpret. However, this study should increase the confidence level for use of the PFC2D program in the future.
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