Tunneling in fault zones, Tuzla tunnel, Turkey

The Tuzla tunnel was excavated mainly in fault zones, shale and limestones using the conventional and shielded tunnel boring machine (TBM) methods. Fault zones in shales are brecciated and clayey, while those in limestones are of blocky structure. The rock mass rating, rock mass classification and support systems proposed for fault zones in Tuzla tunnel are insufficient for explaining the deformation and failure mechanisms encountered in the tunnel. In addition, dyke exposures, the fault-collapsed karstic system and groundwater also caused some problems during the excavation of the tunnel. The most important event relevant to fault zones in the Tuzla tunnel was the selection of a TBM. Before the excavation of the tunnel, the rock was determined to be of poor to fair quality. Therefore, tunneling with a TBM in rock of poor to fair quality was thought to be economic. However, during the excavation, fault zones with poor to very poor rock characteristics were encountered along an area comprising 70% of the tunnel length. The fault zones caused jamming of the TBM cutter and deviation from the tunnel alignment. In this respect, tunneling with the TBM method was quite problematic. Geotechnical problems encountered in the fault zones required special measures to be taken in the tunnel. With these measures, excavation and supporting of the tunnel were completed successfully by transforming heterogeneous conditions in the fault zones to homogeneous conditions in the tunnel impact area.

[1]  E. Hoek,et al.  Estimating the geotechnical properties of heterogeneous rock masses such as flysch , 2001 .

[2]  William A. Wallace,et al.  Large diameter tunneling in a soft clay shale - A case history of the San Antonio flood control tunnels , 1993 .

[3]  George H. Davis,et al.  Structural geology of rocks and regions , 1984 .

[4]  Nick Barton,et al.  A SYSTEM FOR PRESENTATION OF ENGINEERING GEOLOGICAL DATA FOR TUNNEL DESIGN , 1994 .

[5]  H. H. Einstein.  Tunnels in Opalinus Clayshale — A review of case histories and new developments , 2000 .

[6]  Abdel Salam.  Tunnelling and ground conditions , 1994 .

[7]  E. T. Brown.  Rock characterization, testing & monitoring: ISRM suggested methods , 1981 .

[8]  I. S. Cameron-Clarke,et al.  Correlation of rock mass classification parameters obtained from borecore and In-situ observations , 1981 .

[9]  Nuh Bilgin,et al.  The performance prediction of a TBM in difficult ground condition , 1999 .

[10]  S. Dalgıç.  Tunneling in squeezing rock, the Bolu tunnel, Anatolian Motorway, Turkey , 2002 .

[11]  Charles H. Dowding,et al.  Damage to Rock Tunnels from Earthquake Shaking , 1978 .

[12]  Z. Bieniawski.  Engineering rock mass classifications , 1989 .

[13]  E. Broch,et al.  Stability problems in water tunnels caused by expandable minerals. Swelling pressure measurements and mineralogical analysis , 1995 .

[14]  A. Şengör,et al.  The North Anatolian transform fault: its age, offset and tectonic significance , 1979, Journal of the Geological Society.

[15]  Wulf Schubert,et al.  Critical comments on quantitative rock mass classifications , 1999 .

[16]  K. Kovari,et al.  Experience with large diameter tunnel boring machines in Switzerland , 1993 .

[17]  C. Scholz.  The Mechanics of Earthquakes and Faulting , 1990 .

[18]  W. Schubert,et al.  Controllable ductile support system for tunnels in squeezing rock , 1998 .

[19]  E. Hoek,et al.  Applicability of the geological strength index (GSI) classification for very weak and sheared rock masses. The case of the Athens Schist Formation , 1998 .