Controlling Ground Settlement in Urban Mechanized Tunneling through Taking Effective Improvement Measures (Case study: Tehran Subway tunnel, line 7)

Constructing underground spaces causes chaos in the ground stress field and its deformation. Due to settlement، construction of such urban underground spaces as subway tunnels is of utmost importance. In this research، the boring process of Tehran subway tunnel، line 7، has been studied and ground settlements، under Greenfield conditions، have been estimated for 2 sections (km 5+100 and km 9+900). The numerical analyses of the settlements of these 2 sections have been done with the Plaxis 3D software and compared with those recorded on the tunnel axis. It has been shown، through measuring ground settlement of the tunnel nearby buildings، that a relatively symmetrical settlement has been occurred around the tunnel axis. Settlements in these 2 sections، estimated by analytical and numerical methods، were not found to be in the permissible range. Therefore، to control settlement، it is necessary that improving measures be taken; at km 5+100، a coefficient of 1. 6 for the chamber room pressure would suffice and at km 9+900، the tunnel route needs regional improvement to make the work face stable and cause settlements to occur in the permissible limits. The values found by infography confirm those found by this research