The aim of this work is to present the methodology and the results on lowering the water table of the Butia Coal Mine in the state of Rio Grande do Sul, Brazil. The purpose of the study was the creation of safe, stable and economic conditions for mining operations. For the water table modelling, it was employed a software for grid generation and isocontour maps creation. This procedure helps the interpretation and the analyses to establish the aquifer behaviour.
Es wird eine Methode zur Erniedrigung des wasserspiegels vom Butia-Leste Tagebau, Bundesland Rio Grande do Sul, Brasilien, presentiert. Ein mathematisches Modell des Wasserspiegels wird mit Hilfe eines Computer studiert. Die Ergebnisse beweisen die Möglichkeiten sichere, stabile und preiswuerdige Bedingungen von Bergarbeiten zu erreichen und den Wasserspiegel zu bewerten.
Ce travail a par but de presenter la methodologie et les resultats obtenus concernant l'abaissement des couches freatiques de la Mine de charbon de Butia, à l'etat du Rio Grande do Sul, Bresil. II est propose l'etude de la creation des conditions sûres, stables et economiques pour les operations de mineration. Pour la modelisation des couches freatiques, il a ete employe un logiciel pour la creation de grilles et obtention de mapes d'isocontour. Cette procedure a le merite d'aider l'interpretation et l'analyse pour la determination du comportement de l'aquifer.
This paper analyze the behaviour of water table lowering using wells located along the stripping cuts in the Butia-Leste coal mine. A group of piezometers where located for water table level measurements and monitoring. Geological mapping was also performed to add information in the results interpretation. The use of contouring softwares improve the data display and results interpretation.
Coal basins in Rio Grande do Sul are inserted in a great syneclese, with elliptical shape sited on South American Platform (Almeida 1976), named Parana Basin. presented in figure 1. This basin is formed mainly by paleozoic sedimentation with more recent sedimentary covers and mesozoic volcanism associated. Coal bearing strata occur in the Rio Bonito Formation, Guata Group, Tubarao Super Group (Schneider 1974). Such formation presents average thickness, for all the basin of about 150 meters, and its litologies are conditioned by sedimentary facies in which coal seams are inserted. Thus, in the pelitic facies, predominant litologies are siltstones, shales, mudstones and sandstones at the top (characteristic of wash over of shore back barrier). Usually there are conglomerates, mudstones and immature sandstones at the base of the formation. In the sandy facies (fluvio-lacustrine) predominate immature litologies resultant of the higher gradient in the beginning of the deposition. Coal deposits in Rio Grande do Sul, presented in figure 2, generally appear as structural basins controlled by paleorises of tectonic origin or not, tilted to the North of Parana Basin. Normal faults are common in these deposits.
The Butia-Leste coal deposit is inserted in a grabben system filled by conglomerated sedimentation in the bottom, pelites and two coal seams at the top. The coal seams depths varies from 3,00 m to 75,00 m, and its thickness from 2,00 m to 5,30 m. In the west extreme of the south block, the coal deposit is covered by recent fluvial sedimentation, constituted basically by clays, sandy-clays, fine sands and coarse sands in the base with an average thickness of 6,00 m. The minimum and maximum values ranges from 3,50 to 7,50 m.
