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Mine Water and the Environment

, Volume 36, Issue 2, pp 310–322 | Cite as

Water-Isolating Capacity of an Inclined Coal Seam Floor Based on the Theory of Water-Resistant Key Strata

  • Jian Sun
  • Xiexing Miao
Technical Article

Abstract

A model of an inclined coal seam floor with linearly increasing water pressure was developed based on theories of ground pressure and key strata. The stability metrics of the water-resistant key strata in the inclined coal seam was deduced using Mohr–Coulomb yield criterion. Five principle factors were selected: the distance that the workface had advanced, the tilted length of workface, the thickness and pitch of the water- resistant key strata, and the elasticity modulus. A sensitivity analysis was then conducted using an orthogonal design. The thickness of the water-resistant key strata was the most important factor, with a 44.8% ranking, followed by the distance that the workface had advanced at 34.4%. The influence of the elasticity modulus, pitch, and tilted length of the workface, were 9.3, 5.8, and 5.7%, respectively. The maximum water pressure possibly tolerated by the inclined aquiclude were found to rise with the increasing load of the caved overburden, and decrease with the increasing workface initial or periodic weighting distance, workface length, and pitch of the water-resistant key strata. A parabolic relationship exists between the maximum allowable water pressure and thickness of the key aquiclude. Water-resistant key strata located in the lower part of the confining layer offers better protection from floor water inrush. These findings provide an important theoretical basis to determine the potential of water inrush from an inclined coal seam when mining above confined aquifers.

Keywords

Water inrush Prediction model Orthogonal design Sensitivity analysis Geologic setting Mining operation 

Zusammenfassung

Für den Fall einfallender Kohleflöze und unter der Annahme linear ansteigender Wasserdrücke wird ein theoretisches Model auf Basis von Grunddrücken und stratigraphischer Schlüsseleinheiten entwickelt. Die Stabilitätseigenschaft einer wasserundurchlässigen Schlüsseleinheit innerhalb eines einfallen Kohleflözes wird durch das Mohr-Coulomb-Feld-Kriterium bestimmt. Fünf prinzipielle Faktoren wurden in dieser Studie unter der Annahme eines Orthogonalfeldes in einer Sensitivitätsanalyse untersucht: eine zunehmende Entfernung des Abbaustoßes, die geneigte Länge des Abbaustoßes, die Mächtigkeit und das Einfallens der wasserundurchlässigen Schlüsseleinheit und das Elastizitätsmodul. Die Mächtigkeit der wasserundurchlässigen Schlüsseleinheit war der sensitivste Faktor (44.8%), gefolgt von der zunehmenden Entfernung des Abbaustoßes (34.4%). Der Einfluss des Elastizitätsmoduls (9.3%), des Einfallens (5.8%) und der geneigten Länge des Abbaustoßes (5.7%) war weniger sensitiv. Der maximale Wasserdruck, welcher durch den einfallenden Wassernichtleiter potenziell tolerierbar ist, steigt grundsätzlich mit dem statischen Überlagerungsdruck an, fällt jedoch mit steigenden (gewichteten) Abbaufortschritten, der Länge des Abbaustoßes und dem Einfallen der Aquiclude. Zwischen dem maximal zulässigen Wasserdruck und der Mächtigkeit der Schlüssel-Aquiclude besteht eine parabolische Beziehung. Wasserundurchlässige Partien, welche sich im unteren Teil eines Geringleiters befinden, bieten einen größeren Schutz gegenüber Liegendwasser-Einbrüchen. Die hier erzielten theoretischen Studienergebnisse tragen dazu bei, das Potenzial von Wassereinbrüchen über einfallenden Kohleflözen bei Bergbautätigkeiten im Hangenden gespannter Grundwasserleiter besser zu bestimmen.

Resumen

Basado en las teorías de presión sobre el suelo y estratos clave, se desarrolló un modelo que relaciona el piso inclinado de una veta de carbón en forma lineal con el incremento de la presión del agua. Las medidas de estabilidad del estrato resistente al agua en la veta inclinada de carbón se dedujeron utilizando el criterio de Mohr-Coulomb. Cinco factores fueron seleccionados: la distancia de avance de la cara de trabajo, la longitud de inclinación de la cara de trabajo, el espesor y el paso del estrato resistente al agua y el módulo de elasticidad. El análisis se realizó utilizando un diseño ortogonal. El factor más importante fue el espesor del estrato resistente al agua, con 44.8%, seguido por la distancia que había avanzado la cara de trabajo con 34.4%. Las influencias del módulo de elasticidad, paso y longitud de la inclinación de la cara de trabajo, fueron 9,3, 5,8 y 5,7%, respectivamente. La máxima presión de agua posible tolerada por el acuífugo inclinada aumenta con la carga excavada y decrece con el avance de la cara de trabajo o con la distancia ponderada por el peso, la longitud de la cara de trabajo y el paso de los estratos resistentes al agua. Existe una relación parabólica entre la máxima presión de agua admisible y el espesor del acuífugo clave. Un estrato clave resistente al agua y localizado en la parte baja de la capa confinada ofrece mejor protección a la irrupción de agua desde el piso. Estos resultados proveen una importante base teórica para determinar el potencial de irrupción de agua desde una veta inclinada de carbón cuando la minería alcance la zona superior a los acuíferos confinados

Notes

Acknowledgements

This study was supported by the National Natural Science Foundation of China (No. 51404013), the Open Projects of State Key Laboratory of Coal Resources and Safe Mining at the China University of Mining and Technology (No. 13KF01), the China Postdoctoral Science Foundation-funded Projects (No. 2013M540478), and the Natural Science Foundation of Anhui Province (Nos. 1508085ME77 and 1508085QE89).

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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.School of Energy and SafetyAnhui University of Science and TechnologyHuainanChina
  2. 2.State Key Laboratory of Coal Resources and Safe MiningChina University of Mining and TechnologyXuzhouChina

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