Numerical modeling of ground settlement control of large span underground metro station in Tehran Metro using Central Beam Column (CBC) structure

The ground surface settlement caused by underground excavation is an important matter in urban development. The settlement control of large span underground station in Tehran Metro is investigated using a full three-dimensional (3-D) finite element analysis. A method of underground construction by increasing the rigidity of the supporting system using Central Beam Column (CBC) structure is introduced. In construction of large underground space, effect of presence of CBC structure is compared to a case without CBC structure. The CBC structure increases the rigidity of supports and decrease the stress concentration and displacement in supporting system. It generally decreases the soil deformation above the underground space resulting in smaller ground surface settlement.Influence of spacing of central columns and their dimensions on the magnitude of settlement are also investigated in this study. Effect of ground improvement of Tehran soil by consolidation grouting on ground surface settlement and stress distribution in supporting system is modeled and analyzed. It can be concluded that in an urban area over a large underground spaces (e.g., underground metro stations) with relatively low overburden similar to northern Tehran, CBC structure can be very effective and reliable measure in controlling and reducing the surface settlement and the stress concentration on initial supporting system.

► Central Beam Column (CBC) structure is introduced in a staged construction of a large underground.
► Settlement control over an underground Metro station in Tehran is investigated using 3D FE analysis.
► Cases of system with, without CBC and of an improved ground by consolidation grouting are compared.
► CBC is a reliable and effective way in controlling settlement and stress concentration in supports.
► CBC as a controlled and permanent structure, is more reliable and durable support in its life time.