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Assessment of Dewatering Requirements and Dewatering Well Design for an Open Pit Coal Mine in Central Anatolia

Abstract

The Çeltikçi Coal Basin is a newly discovered coal basin in Central Anatolia where 11 years of open-cut mining has been planned. The bulk of the mining will be conducted below the regional water table; hence, determination of the dewatering requirements and proper design of the dewatering wells plays a critical role. This study (i) defined the dewatering requirements of the open-pit mine, (ii) established a dewatering well design for the area, and (iii) assessed the anticipated impacts of the dewatering activities. For this purpose, a 3-D numerical groundwater flow model was developed using the FEFLOW software. Yearly dewatering requirements were determined under transient conditions. For the dewatering well simulations, two types of dewatering wells were considered: permanent wells located at the open pit boundary that would increase in number as the excavation proceeds and wells located at the periphery of the yearly excavated area that would be operational for about two years. The simulation results indicated that 894 wells were required to satisfy dry working conditions; the average pumping rate throughout the mine life was calculated as 322 L/s. The impacts of open-pit dewatering on groundwater resources were assessed in terms of spring discharge and base flow rates in the nearby Kirmir stream. As a result of dewatering, most of the village water supply springs and fountains will dry up in the area. In addition, the base flow rates to the Kirmir stream will be decreased by 15%.

Resumen

La cuenca carbonífera de Çeltikçi es una cuenca de carbón recién descubierta en Anatolia Central en la que se han previsto 11 años de explotación a cielo abierto. La mayor parte de la explotación se llevará a cabo por debajo del nivel freático de la región, por lo que la determinación de los requisitos de desagüe y el diseño adecuado de los pozos de desagote desempeñan un papel fundamental. Este estudio (i) definió los requisitos de desagote de la mina a cielo abierto, (ii) estableció un diseño de pozos de desagote para la zona y (iii) evaluó los impactos previstos de las actividades de desagote. Para ello, se elaboró un modelo numérico tridimensional de flujo de aguas subterráneas utilizando el software FEFLOW. Se determinaron las necesidades anuales de desagote en condiciones transitorias. Para las simulaciones de pozos de desagote, se consideraron dos tipos de pozos de desagote: pozos permanentes situados en el límite del tajo abierto que aumentarían en número a medida que la excavación avanzara y pozos situados en la periferia de la zona excavada anualmente que estarían operativos durante unos dos años. Los resultados de la simulación indicaron que se necesitaban 894 pozos para satisfacer las condiciones de trabajo en seco; la tasa media de bombeo a lo largo de la vida de la mina se calculó en 322 L/s. Se evaluaron los impactos del desagote del tajo abierto en los recursos de agua subterránea en términos de descarga de manantiales y caudales base en el cercano arroyo Kirmir. Como consecuencia del desagote, la mayoría de los manantiales y fuentes de suministro de agua del pueblo se secarán en la zona. Además, los caudales de base del arroyo Kirmir disminuirán en un 15%.

Zusammenfassung

Das Çeltikçi-Kohlerevier ist ein neu entdecktes Kohlebecken in Zentralanatolien, in dem für 11 Jahre tagebaumäßige Gewinnung geplant wird. Der größte Teil des Abbaus wird unterhalb des regionalen Grundwasserspiegels erfolgen. Daher spielen die Festlegung der Entwässerungsanforderungen und die richtige Auslegung der Entwässerungsbrunnen eine entscheidende Rolle. Im Rahmen dieser Studie wurden (i) die Entwässerungsanforderungen für den Tagebau definiert, (ii) ein Entwässerungsbrunnenkonzept für das Gebiet erstellt und (iii) die zu erwartenden Auswirkungen der Entwässerungsaktivitäten bewertet. Zu diesem Zweck wurde ein numerisches 3-D-Grundwasserströmungsmodell mit der Software FEFLOW entwickelt. Die jährlichen Entwässerungsanforderungen wurden unter instationären Bedingungen festgelegt. Für die Entwässerungsbrunnensimulation wurden zwei Arten von Entwässerungsbrunnen berücksichtigt: permanente Brunnen an der Tagebaugrenze, deren Anzahl mit dem Abbaufortschritt zunehmen würde und Brunnen am Rande der jährlichen Abbauflächen, die etwa zwei Jahre lang in Betrieb sein würden. Aus den Simulationsergebnissen geht hervor, dass 894 Brunnen erforderlich sind, um trockene Arbeitsbedingungen zu gewährleisten. Die durchschnittliche Pumprate über die gesamte Tagebaudauer wurde mit 322 l/s berechnet. Die Auswirkungen der Tagebauentwässerung auf die Grundwasserressourcen wurden im Hinblick auf die Quellschüttung und die Grundwassermenge des nahe gelegenen Kirmirbachs bewertet. Infolge der Entwässerung werden die meisten Quellen und Brunnen zur Wasserversorgung der Dörfer in diesem Gebiet versiegen. Außerdem wird der Niedrigwasserabfluss des Kirmirbachs um 15% sinken.

评价安纳托利亚 (Anatolia) 中部露天煤矿疏干目标需求与疏水井设计

Çeltikçi煤炭盆地是在安纳托利亚 (Anatolia) 中部新发现的一个含煤盆地, 已经规划了11年露天开采。大部分煤炭开采将位于区域地下水位以下。因此, 确定地下水疏干目标要求和合理疏水井设计至关重要。研究: (i) 确定了露天矿的地下水疏干目标要求; (ii) 给出了研究区疏水井设计; (iii) 评价了疏水活动的预期影响。为此, 用FEFLOW建立了三维地下水流数值模型。确定了瞬态 (非稳定) 的年疏干水量目标要求。在疏干井模拟时, 考虑了两类疏水井: 位于露天矿边界的数量随采掘推进而增加的长期疏水井和位于年采掘区外缘的运行期约两年的疏水井。模拟结果表明, 满足疏干工作条件需要894口井, 矿井整个服役生命期的平均抽水量为322升/秒。依据泉水流量和附近Kirmir河的基流量评价了露天矿疏干工程对地下水资源的影响。由于疏水, 区内大部分村庄的供饮泉水和喷泉将干涸。同时, Kirmir河的基流量将减少15%。

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Acknowledgements

This project was funded by IKA Mining Inc. through projects No. 11-03-09-02-00-36, No. 14-03-09-02-00-03, and No. 14-03-09-02-00-21 given to Middle East Technical University. The opinions, findings, conclusions, and recommendations expressed are those of the authors and do not necessarily reflect the views of IKA Mining Inc. The positive and constructive comments provided by the reviewers are greatly appreciated.

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Correspondence to Ayse Peksezer-Sayit.

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Peksezer-Sayit, A., Yazicigil, H. Assessment of Dewatering Requirements and Dewatering Well Design for an Open Pit Coal Mine in Central Anatolia. Mine Water Environ (2022). https://doi.org/10.1007/s10230-022-00877-4

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Keywords

  • FEFLOW
  • Numerical modeling
  • Çeltikçi coal basin
  • Groundwater inflow