3D Numerical Investigation of Ground Settlements Induced by Construction of Istanbul Twin Metro Tunnels with Special Focus on Tunnel Spacing

  • Behnaz Hallaji Dibavar Department of Mining Engineering, Hacettepe University, 06800 Beytepe, Ankara, Turkey
  • Mohammad Hossein Ahmadi Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, 424 Hafez Ave, Tehran, Iran
  • Seyed Morteza Davarpanah Department of Engineering Geology and Geotechnics, Faculty of Civil Engineering, Budapest University of Technology and Economics, H-1521 Budapest, P.O.B. 91, Hungary

Abstract

One of the most important considerations of tunneling in urban areas is controlling the amount of surface settlement that occurs during construction stages. The goal of this paper is to investigate the effect of spacing of Istanbul Twin Metro Tunnels on the surface settlement excavated by NATM method in YENIKAPI-UNKAPANI metro line. For this purpose, the focus has been placed on the effect of longitudinal and transversal spacing between tunnels supported by an umbrella arch protecting method. (FLAC3D) was implemented to simulate the excavation sequence. According to the analysis, the amount of settlement by numerical approach was about 23.5 mm which was in good agreement with the field monitoring results that was 26.5 mm. Moreover, the interaction between twin tunnels by the increase in spacing between twin tunnels in the direction perpendicular to tunnel axis decreases and becomes less effective at the location about 3 times of the tunnel diameter. Similarly, the interaction between twin tunnels in the direction parallel to tunnel axis decreases as the spacing increases. In other words, by increasing the distance between tunnel faces in longitudinal direction at a distance about 3 times of the tunnel diameter, there is still interaction between tunnels and it doesn’t disappear completely. Therefore, it is recommended to keep this distance at about more than 2.5 times of tunnel diameter so that settlement can stay within acceptable range.

Keywords: surface settlement, NATM method, umbrella arch protecting method, FLAC 3D
Published online
2019-12-10
How to Cite
Hallaji Dibavar, B., Ahmadi, M., & Davarpanah, S. (2019). 3D Numerical Investigation of Ground Settlements Induced by Construction of Istanbul Twin Metro Tunnels with Special Focus on Tunnel Spacing. Periodica Polytechnica Civil Engineering, 63(4), 1225-1234. https://doi.org/10.3311/PPci.14591
Section
Research Article