Influence of the geometric characteristics of wedges on the safety of Vrasna tunnel in Egnatia highway, N. Greece


Published: Jan 1, 2007
Keywords:
Shotcrete rock bolts rock mass quality
M. Chatziangelou
B. Christaras
Abstract

The present paper concerns the influence of the geometric characteristics of the potential wedges on tunnels safety, which are supported by shotcrete and rock bolts, during the excavation of poor and medium quality rock mass, in accordance to RMR classification system. The geological and tectonic data which were used in our estimations were collected in situ during the excavation of Vrasna's tunnel. According to shear test along discontinuities planes, friction angle was considered 21° on schistosity planes and 35° on joint planes. Furthermore, no cohesion was taken into account, as the fractures were, more or less, opened. The orientation and spacing of discontinuities were taken into account for estimating tunnel stability, given that they affect the strength and the quality of the rock mass during the construction. The collected data and the obtained, after elaboration, results were correlated statistically and power regressions were determined

Article Details
  • Section
  • Engineering Works and Geological Applications
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References
Bieniawski, Z.T., 1989. Engineering rock mass classifications, New York: Wiley.
Chatziangelou, M, and Christaras, Β., 2003. Shotcrete application effectiveness as support measure at poor quality rock masses, Proc. International Symposium of Industrial Minerals and Building Stones, Konstantinoupolis, Turkey, 745-749pp.
Christaras, Β., Chatziangelou, M., Malliaroudakis, Em., and Merkos, S., 2002. Support Capacity of wedges and RMR classification along the Asprovalta tunnel of Egnatia Highway, in n. Greece, 9th Congress of the International Association for Engineering Geology and the Environment, J.L, van Rooy and CA. Jermy, ISBN No.0-620-28559-1.
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Hoek, E., Kaiser, P.K., and Bawden, W.E., 1995. Support of underground excavations in hard rocks, Balkema Pbl, Roterdam, 215p.
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