S.M ALAVI - Structure Expert, Department of Hydraulic Structures, Mahab Ghods consultant engineering Company, Tehran, Iran
H Farzanegan - Head of Structure Technical Deputy, Department of Hydraulic Structures, Mahab Ghods consultant engineering Company,Tehran, Iran

When a tunnel passes through an active fault, it will be subjected to extra stresses caused by fault displacements. However these stresses are reduced when the tunnel is constructed into several small segments near faulted zone, their magnitudes are still considerable and can damage the tunnel segments in long time. This research intends to investigate of influence of a viscoelastic material injection into fault surface on reduction of the stress magnitudes in tunnel segments, when the fault moves. The creep phenomenon in viscoelastic materials results in a softening trend in injected zone as time passes. The displacement of the softened soil around the tunnel segments induces smaller stresses in tunnel segments in comparison to the un-injected state considerably. So, it is concluded that this type of injection according to appropriate mechanical parameters of the injected material, makes the tunnel more flexible against fault displacements because of the composite performance.

tunnel segment, faulted zone, viscoelastic material, flexibility, composite performance