Abstract:

FLAC software is used to simulate the mechanisms of the ground deformations caused by tunnel excavation in silty sand layers where there exists hard shell on the ground surface. By means of analyzing on the characteristic curves of the spatial effects of the ground deformations caused by the tunnel excavation, the amplitude and scope of the ground deformations caused by the excavation and reinforcement of the tunnels are determined and the most adverse loading conditions of the tunnel excavation and the weak positions of the structures are obtained, which provides theoretical basis and decisionmaking support for the selection of the construction alternatives. The study indicates that different construction sequences lead to different construction mechanical states, which in turn lead to different construction mechanical effects. Furthermore, different construction sequences lead to different disturbance areas and different disturbance amplitudes. On basis of the measurement data of a station of Beijing Metro, the article analyses on the ground deformations caused by tunnel construction in silty sand layers and recommends some countermeasures for the ground deformations.

Key words:  , tunnel small spacing  , ground deformation countermeasure