فرزاد کامکار

Due to the population growth and the increasing demand for the construction of the infrastructure necessary for comfortable and fast transportation, tunneling has become especially important. Tunneling in urban areas by passing underneath several buildings causes subsidence due to stress relief and development of elastic and plastic deformations. If these subsidences are not controlled, the structures on the ground will be seriously damaged. Thus, proper estimation of subsidence is an important task when doing tunneling feasibility in urban areas. Nowadays, several methods are used for tunnel analysis and design and for urban tunnels, which excavated in shallow and soft grounds, the best way is using numerical methods. The study of excavation impact on stress distribution around tunnels as well as the study of ground surface subsidence in soft grounds are extremely important and should be deeply taken into account. This research addressed the 2D modeling of Modarres Tunnel of Arash-Esfandiyar-Niyayesh Tunnel Project by PLAXIS software. This tunnel is located in The Third Region of Tehran Municipality. The subsidences were determined through numerical modeling by hardening soil behavioral model, and, then, were compared to the results of the modeling by Mohr-Coulomb behavioral model. it was concluded that the excavation of Modarres tunnel, considering the modeling results and comparing them to the monitoring data, could be done in a controlled and safe manner by using NATM sequential excavation method and by utilizing the soil reinforcement elements such as fore-poling, nailing and micro-piles, and this experience should be used in similar tunneling sections. Furthermore, the use of hardening soil model was more appropriated for modeling the tunnel in the coarse-grained soil in Tehran which had the same conditions as this tunnel, than the Mohr-Coulomb model. The maximum subsidence in the modeling with the hardening soils model and the Mohr Coulomb model was 23.37 mm and 27.04 mm, respectively.