ABSTRACT
The current study addresses the various types of challenges and geological hazards during tunnel excavation by mechanized tunneling method (TBM) in Tehran Alluvium conditions. In addition to introduction of tunnel construction projects in the city of Tehran, challenges existing in their implementation along with strategy and solutions to deal with them, which are considered as valuable experiences of the projects, are described in this study. The results of this study showed that among the various hazards that occur during the excavation of a tunnel, eleven hazards are more important than other hazards, such as abrasion of the machine cutting tools, clogging around the machine cutting tools, soil mass displacement in the tunnel face, liquefaction, sand lenses, soil-sand tunnel face, severe water column fluctuations, collapse of the tunnel ceiling and instability in its walls, high soil penetrability, lack of fine-grained materials, and presence of boulders and cobbles. Also, in this study, Tehran’s zoning maps for two standard parameters, standard penetration test (SPT) N-value and percentage of fine-grained particles are provided. Some of the most important features of the sediments in Tehran which can be problematic for tunnel excavation are presented by the help of these maps.
