Two-dimensional numerical analysis of tunnel collapse driven in poor ground conditions

Türkoğlu, Melih
Insufficient information on the host medium can cause serious problems, even collapse, during construction in a tunnel. This study focuses on understanding the reasons behind the collapse of the Tunnel BT24 to be opened within the framework of Ankara-İstanbul High Speed Railway Project. The tunnel is located near Bozüyük in the Bilecik Province. The collapsed section of the tunnel was driven into a highly weathered, weak to medium rock mass. Unanticipated geological/geotechnical circumstances caused excessive deformations at the section on which the primary support system was applied, leading eventually to collapse. To understand the response of the tunnel and the collapse mechanism, the construction sequence is simulated using two-dimensional plane-strain and axisymmetric finite element models. The analyses were carried out for the section with and without invert closure of the shotcrete liner. To implement the effects of likely unfavorable ground conditions on the tunnel response, a number of fault scenarios and possible creep effects were also considered with those two alternatives. Displacements in the tunnel periphery, forces and moments in the primary liner as well as the plastic deformation zones in the surrounding ground were determined for each case and comprasions were made accordingly. İt is concluded that the unforseen ground circumstances might have substantially aggravated the deformations in the section and that the lack of ring closure of the primary liner at invert played the key role in the collapse.


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There are some difficulties in the construction of precast conventional reinforced concrete tunnel segments. Due to corrosion problem of ordinary reinforcement, the task becomes more complicated. Moreover, the workmanship for the construction of segments is also very time consuming. There are some research for the design of tunnel segments with fiber reinforced polymer (FRP) bars. Besides, guidelines for the design of fiber reinforced concrete (FRC) tunnel linings are also available. This thesis provides a ...
Citation Formats
M. Türkoğlu, “Two-dimensional numerical analysis of tunnel collapse driven in poor ground conditions,” M.S. - Master of Science, Middle East Technical University, 2013.