Investigating the Effect of Fault on Displacement, Subsidence and Tunnel Safety Factor (Case Study: Noghre Kamar Tunnel)

Tunnel design and construction in developed and developing countries have been widely considered by government officials to maximize the use of underground space. Meanwhile, the presence of groundwater, crushed rock masses and faults are among the problems of the tunnel passage that seriously affect the underground space. If for any reason the tunnel route cannot be changed, the tunnel can be designed and implemented in the vicinity of the fault with safety solutions. The accuracy of the correct design of these tunnels is due to the passage of the fault through or near the tunnel, which are of special economic and safety importance. Therefore, in this article, the effect of the fault around the Noghre Kamar tunnel located in Markazi province with different directions and different distances on a tunnel was investigated, and these results and suggestions can have significant recommendations for designers. This analysis has been investigated using finite element numerical modeling (Plaxis) and finite difference (FLAC).The results show that with increasing the distance of the fault from the tunnel axis, the amount of displacement and damages are significantly reduced and with increasing the thickness of the fault, the opposite is true. The average maximum displacement obtained from Plexis and Falak software is 17 and 17.5 cm, respectively, in the case of a 90-degree fault with a width of 3 meters, and in the case where the fault intersects the tunnel at a 45-degree angle, it is 13 and 13.5 cm, respectively. Also, the total stress changes in the position where the fault intersects the tunnel at an angle of 45 degrees is the minimum and in this position the maximum value of the safety factor is obtained.