ABSTRACT
After decades of operating, the function of waterproof of sealing rod has already reduced to a low grade for the non-uniform settlement of tunnel caused by adjacent construction, pumping of ground-water, etc. For the special stress state, most segment rings exhibit an ellipse shape with horizontal radius enlarged and vertical radius reduced. Correspondingly, the compressive stress at the hance of tunnel segment ring decrease near outer surface and increase near interior surface. Gaps at the joint of segment rings maybe formed. Since the sealing rod was set at the outer side of segment ring, so the capability of water-proof was reduced at the hance of the tunnel, and this lead to that most leakage take place at the side of tunnel. In addition, for the great difference of structural style among the shield tunnel, the station and the by-pass, differential settlement occurs at these positions and this also leads to serious seepage.
