Study on the Interaction Mechanism of Segments in the Stratum of TBM Tunnels Undercrossing Existing Buildings

Surface settlement caused by tunnel excavation is an inevitable phenomenon in urban subway tunnel construction, which may cause irreversible damage to the ground roads, buildings, etc., if not controlled. Therefore, reasonable prediction and control of surface settlement are essential to ensure the safety and efficiency of tunnel construction.

Based on the numerical analysis method, this paper establishes a three-dimensional mechanical calculation model of a TBM tunnel (diameter 6 m) crossing existing buildings (4-story frame structure) and studies the influence law of tunnel excavation on stratum deformation and segment stress.

The results show that (1) the stress and displacement of the segments vary with the position, and the segments under the building are most affected by the building, whose vertical stress is much greater than the horizontal stress. (2) The vertical displacement of the segments is the largest at the vault and arch bottom and increases with the segments approaching the building, while the horizontal displacement is the largest at the arch waist and shows negative values along the tunnel axis. (3) When the tunnel is excavated to a distance of one tunnel diameter from the building, the building will be affected. If the stratum is unstable, it may cause the collapse of the excavation face or surface settlement, which may result in building inclination, cracking or uneven settlement.

The research results of this paper can provide a reference for the construction parameter optimization and risk control of TBM tunnel crossing existing buildings.