Tunnel Rehabilitation in Fault Zone Using Sequential Joints Method- Case Study: Karaj Water Conveyance Tunnel

The lining structure of Tunnel Boring Machine (TBM) excavated tunnels is composed of series of precast Reinforced Concrete (RC) pieces which are called segment. At the present paper, a novel method is introduced for seismic retrofitting of segmental tunnels located at active fault zones in rock environment with case study of Amirkabir dam to Tehran water transfer tunnel (Karadj tunnel). The main design concept in this method is based on stiffness degradation of the tunnel structure intersecting tunnel with fault central zone. Even the strongest structures are not capable to undergo displacement of faults and will fail; so, the stiffness degradation and providing life safety operational limit is the logical solution. This phenomenon is developed due to creation of sequential joints‌ in segments intersecting tunnel with fault central zone; so, it is called sequential joints method. At this method, a joint is considered between each or multiple rings and using this method, the tunnel structure is synchronized with tunnel displacements during fault displacement process and the global failure of the tunnel structure is avoided. This method is currently applied in second part of Karadj water transfer tunnel (Part K”-BR).