Analysis of support requirements for a shallow diversion tunnel at Guledar dam site, Turkey H. Basarir a, * , A. Ozsan b , M. Karakus a a Department of Mining Engineering, Inonu University, 44280 Malatya, Turkey b Department of Geological Engineering, Ankara University, 06100 Ankara, Turkey Received 25 March 2005; received in revised form 21 July 2005; accepted 22 July 2005 Available online 16 September 2005 Abstract Engineering geological properties and support design of a planned diversion tunnel at Guledar dam site, which was located at the North of Ankara, Turkey were studied in this article. The main purpose of the construction of the planned tunnel is to regulate, drainage and to provide water for irrigation purposes. The diversion tunnel runs mainly through formations of limestone, sandstone and diabase. Rock masses at the site were characterized using Rock Mass Rating (RMR), Rock Mass Quality ( Q), Rock Mass Index (RMi) and Geological Strength Index (GSI). RMR, Q, RMi and GSI were determined by using field data and mechanical properties of intact rock samples, measured in the laboratory. Support requirements for the planned diversion tunnel were determined accordingly in terms of the rock mass classification systems. Recommended support systems by empirical methods were also analyzed using 2D Finite Element method. Calculated parameters based on empirical methods were used as input parameters in the finite element models. The results from both methods were compared with each other. This comparison suggests that more reliable support design could be achieved by using the finite element method together with the empirical methods. D 2005 Elsevier B.V. All rights reserved. Keywords: Rock mass classification; RMR; Q; RMi; GSI; Convergence–confinement method; Hoek–Brown failure criterion; Finite element method; Tunnel support design 1. Introduction Empirical and numerical methods are commonly used methods when underground engineering struc- tures are designed. Empirical methods are generally preferred by rock engineers and engineering geolo- gists due to their practicality. In designing tunnel supports, rock mass classification systems, RMR, Q and RMi have been used by many researchers and gained a universal acceptance. These classification systems have been originally obtained from many tunneling case studies and they have been applied to many construction designs. However, these empirical 0013-7952/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.enggeo.2005.07.010 * Corresponding author. Tel.: +90 422 3410030; fax: +90 422 3410046. E-mail address: hbasarir@inonu.edu.tr (H. Basarir). Engineering Geology 81 (2005) 131 – 145 www.elsevier.com/locate/enggeo