Abstract: To explore the difference between the excavation of curved and straight tunnels on the surrounding soil and tunnel structure, 3D numerical models for straight and curved tunnels′ excavation are established respectively to analyze the physicomechanical parameters of the strata and shield structure and the construction load parameters such as shield jacking force are examined. Then, the numerical simulation results are compared with the monitored data of the project to validate the feasibility of the models and analyze the difference of strata displacement and segment strain between the two models. Finally, the influence of unbalanced jacking force on soil displacement and segment strain during curved tunnel excavation is analyzed under conditions with various jacking force ratios and deflection angles. The results show the following: (1) Compared with the straight tunnel, the excavation of the curved tunnel results in an increase in soil settlement above the crown, range of settlement, and segment strain. (2) With the increasing jacking force difference and deflection angle of shield, the uneven surface settlement increases, the asymmetry of horizontal displacement of inner and outer soil increases, and the increment of radial and axial strain of segment increases. (3) The distribution of radial strain of segment varies due to different jacking force directions (inner side and outer side), and when the jacking force direction is outer side, the segment is prone to crack in the range of 75°~135° and 180°~285°. (4) When the unbalance degree of jacking force is over large, the radial strain of the entire segment varies sharply, bringing adverse affect to the structure.

Key words:

curved shield tunnel, soil displacement, segment strain, unbalanced jacking force, numerical simulation