Study of the Effect of Cross-sectional Geometry of Single and Twin Tunnels on the Ground Surface Settlement (Case study: Isfahan’s Metro Tunnel)

Worldwide, rapid population growth in major cities has resulted in increased pressure on existing transportation systems. With underground transportation systems already in place, newly constructed tunnels might be needed to construct in close proximity to each other to make efficient use of the underground space (Baziar et al., 2016; Maleki, 2001). With population growth and urbanization, opening metro tunnels is an effective method for reducing traffic congestion in urban areas. Metro tunnels tend to be in the form of twin tunnels and close to each other or urban infrastructures. In these conditions, the interaction between tunnels and consequently their effects on subsurface movements, ground surface settlement, distribution of induced stresses and properties of tunnel lining are the most important factors that must be considered in tunnel design. Consequently, the above listed parameters have been studied by using a variety of approaches, including in situ observation, physical model testing and numerical modeling (Peck 1969; and Ranken, 1977; Karakus et al. 2007, Talebinejad et al. 2014; Yasitli, 2014).