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Hydrological modeling of open pit mining


This Project develops the numerical modeling of the groundwater flow in a carbonate formation where an open pit mine exists. The formation is called Montaña’s Limestone (mountain’s limestone).

As the mine deepens and extends laterally along the years, the water volume to be extracted with an adequate pumping system increases. The water comes partly from the runoff –especially when rain’s intensity is very high- and, above all, from the interior of the limestone formation itself. The flow path is not uniformly distributed. There are preferential flow paths and heterogeneity has to be taken into account.

In collaboration with specialized staff from the company, we have obtained an updated detailed geological map of the watershed, including lithology and fracture networks. A complete inventory, as well, of groundwater points has been described. With this information, various conceptual models have been proposed on which the numerical models have been built, both in steady state and a preliminary transient one.

The numerical models themselves have been simultaneously performed using two broadly known codes: MODFLOW –based on the finite difference method- and FEFLOW –a finite element solver-. Consistency has been checked along the sequential modeling procedure.

Measures of flow and piezometric heads have been employed as observed data to calibrate the numerical models. Useful applications of the definite model are:

  • The model integrates in a coherent way the previous existing information related to the water in that quarry. This allowed proposing a set of optimized tests.
  • An estimate of the outflows expected for the future, at greater mine depths has been obtained. Of course, when dealing with predictions we have to be prudent.
  • Exploitation parameters have been calibrated using the model. In particular, some estimates of maximum formation thickness have been obtained.

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