Analysis of longitudinal profile of the tunnels in the active faulted zone and designing the flexible lining (for Koohrang-III tunnel)

This paper presents a method of designing flexible lining for tunnels within the regions of active faults. The design criterion is based on the allowable longitudinal deflection and/or angular distortion. Besides the design of flexible joints, the longitudinal deformation profile is also determined within the active faults region. This analysis indicates that if the lining is designed to tolerate an angular distortion about 1-2° along its length, a circular tunnel of 4 m diameter can stand safe and without any damages for the assumed life time. This requirement can be satisfied by introducing some flexible joints between two consequent rigid parts of lining to make it flexible enough to be able to tolerate the moment and shear which may happen in it. It is worth mentioning that the present approach is basically for a particular case in Iran that should be considered as a very risky and critical position.