Abstract:

A 3D numerical model is established by FLAC3D based on fluidsolid coupling effect, so as to simulate and verify the process of instability of tunneling face; moreover, the influences of water level and seepage time on tunneling face deformation, ground settlement and pore pressure are discussed. The study results show that: 1) The developing process of tunneling face deformation can be divided into 3 stages relating with expansion of soil plastic zone. 2) Compared to the case without hydraulic pressure, the stability of tunneling face accounting for fluidsolid coupling effect is significantly reduced; with the increase of water level and seepage time, the limiting supporting pressure to maintain stability increases gradually. 3) The support pressure is characterized by support pressure ratio; the reduction of the supporting pressure would induce the decrease of pore pressure at the front of tunneling face; the pore pressure near tunneling face is affected much more, which features funnelshaped influence zone. 4) When collapse occurs to tunneling face, the significant settlements and soil displacement field of the ground would extend to ground level; and the horizontal displacement at the center of tunneling face correlates with the maximum ground settlement, showing parabolic correlation and linear correlation at different stages.

Key words: shield tunnel, stability of tunneling face, fluidsolid coupling, supporting pressure, ground deformation, pore pressure