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3D numerical investigation of the effects of driving of the new mechanized tunnel on existing segmental linings and ground surface settlements - a case study: Shiraz metro line 2

ABSTRACT Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors (centre-to-centre distance between twin tunnels and soil types in which tunnels are excavated) on the twin-tunnel interaction have been investigated. It is concluded that with pillar widths almost three times greater than the tunnel diameter, the twin-tunnel interaction effects seem negligible.