Abstract:A 3D finite element model has been established to investigate the influences of various factors on the longitudinal mechanical behavior of special-shaped shield tunnel structure comprehensively. The results show that: the overall displacement along the longitudinal direction of special-shaped shield tunnel is downward, and the displacement curve can be represented by a cubic polynomial; the longitudinal effective rigidity ratio initially decreases and then increases with the magnitude of the transverse effective rigidity ratio; the effect of transverse effective rigidity ratio on the longitudinal stiffness is minor, and the recommended design value is 0.65; the longitudinal effective rigidity ratio decreases with the increasing depth under both staggered joint assembling and straight joint assembling conditions; the longitudinal reinforcing effect leads to a larger longitudinal stiffness for staggered-jointed structure than that for straight-jointed structure in soft ground; the coefficient of subgrade reaction has the most evident impact on the longitudinal effective rigidity ratio, which increases linearly with the growth of the coefficient of subgrade reaction; the amount of the longitudinal pre-tightening stress of bolts also leads to a linear increasing trend of the longitudinal effective rigidity ratio, but the impact is not obvious. Finally, a simplified analytical model based on the measured value of the opening amount of the ring seam has been proposed to determine the longitudinal equivalent rigidity and the longitudinal effective rigidity ratios. The effectiveness of the model has been verified by comparing the predicted values with results of the numerical calculations.
