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Evaluation of a slate extraction bank

Abstract To mechanize extraction from a slate quarry it is important, first, to assess the quality of both the slate bed and the slate and to estimate the potential economic yield, so as to optimize the outcome of cuts made in the extraction bank. A methodology is described that can be used as a support by those in charge of slate extraction. The first phase consists in definition of the geotechnical parameters that affect the extraction bank and the aesthetic parameters that affect the slate quality. The second phase involves the application of multivariate techniques with a view to establishing a recovery factor for the slate resource and a quality index for the block of slate, with variation intervals established for the rock faces and samples analysed. The third phase consists in the use of geostatistical techniques to extrapolate the values obtained to the interior of the extraction bank. This enables the quality of the entire deposit to be assessed and permits mechanized cutting tasks to be planned in such a way as to optimize the results. The fourth phase is an a priori financial evaluation of each part of the bank so as to optimize exploitation, the final task being to validate the results in several instances of exploitation.