Abstract
The paper reports an assessment of the engineering geological characteristics of the rock mass to be encountered between Mecidiye and Gazino stations on the new extension of the Ankara metro and the determination of appropriate support and excavation methods. The rock mass quality was estimated using the rock mass rating (RMR), geological strength index (GSI) and rock mass quality (Q) systems and the tunnel divided into sections. The RMR, Q and NATM systems were used to determine the support and excavation methods in these areas. The deformations and stress concentrations around each tunnel section were investigated and the interaction of the support systems with the rock mass was analyzed using finite element software. It is concluded that rock mass classification systems should be used in tandem with numerical tools, although it is emphasized that the estimation of rock mass properties is not an exact science and both rock properties and numerical models should be refined based on observations and the results of instrumentation installed during the construction of a tunnel.
Résumé
L’article présente une évaluation des caractéristiques géotechniques des massifs rocheux devant être rencontrés entre les stations de Mecidiye et Gazino pour la nouvelle extension du métro d’Ankara, ainsi que la définition des soutènements appropriés et des méthodes d’excavation. La qualité des massifs rocheux a été estimée à partir de la méthode rock mass rating (RMR), la méthode geological strength index (GSI) et l’indice qualité Q (Q system), le tunnel étant divisé en plusieurs sections. Les méthodes RMR, Q système et NATM ont été utilisées pour définir les soutènements et méthodes d’excavation adaptées aux différentes sections. Les déformations et concentrations de contraintes relatives à chaque section de tunnel ont été étudiées et les interactions entre les dispositifs de soutènement et les massifs rocheux ont été analysées avec un logiciel aux éléments finis. L’article conclut que les méthodes de classification des massifs rocheux devraient être utilisées conjointement avec les outils numériques, bien que qu’il soit souligné que l’estimation des propriétés des massifs rocheux n’est pas une science exacte. A la fois la détermination des propriétés des massifs rocheux et les modèles numériques devraient être affinés sur la base d’observations et des mesures issues des dispositifs de surveillance installés pendant la construction d’un tunnel.
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Acknowledgments
The authors would like to express their gratitude to the Greater Municipality of Ankara, General Directorate of EGO managers for their kind assistance throughout the project.
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Özsan, A., Başarır, H., Yüceel, S. et al. Engineering geological evaluation and preliminary support design for the metro extension tunnel, Ankara, Turkey. Bull Eng Geol Environ 68, 397–408 (2009). https://doi.org/10.1007/s10064-009-0192-3
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DOI: https://doi.org/10.1007/s10064-009-0192-3