| The different geological setting and construction conditions will lead to the uneven longitudinal settlement of tunnel embedded in poor silty clay. And uneven longitudinal settlements will lead to over-stress the tunnel concrete segmental lining. The stress concentration will induce lining segment cracking, joint bolts yielding, joint dislocation and joint tenon crushing, which all will result in serious slurry and water leakage problems. These issues may bring great risk to metro operations and cause serious risks to the people travelling by subway. Therefore, the causes of the uneven settlement of tunnel and the failure mechanism of the tunnel lining and joints should be determined, insuring normal operations of metro, especially in deep soft soils.In recent years, the research of tunnel longitudinal settlement increases gradually. However, most of the studies focused on the tunnel settlement during construction stage, the influence on the surrounding environment, the long-term regularity of settlement and the tunnel lining design. The study of the causes of tunnel longitudinal settlement and the failure mechanisms of the tunnel is not enough.In general, some developments for tunnel longitudinal settlement are involved in this dissertation as follows:(1) The various causes of tunnel settlement and induced tunnel longitudinal deformation are summarized. On basis of these studies, the tunnel deformation and settlement during global leakage and local leakage were analyzed(2) The undrained deformation and the settlement induced by residue pore pressure dissipation under vibration load during the operation period were analyzed. Three main factors of tunnel settlement were compared and the ratios of the working factors were analyzed in different leakage conditions and geological settings.(3) To simulate the failure mechanism of tunnel segmental lining joints and longitudinal bolts under uneven longitudinal ground settlement, a numerical model with3D lining rings and bolts was established. The interactions between the lining tenons, bolts and their holes were determined. The results indicated that the deformation of the circumferential joints consisted of opening and dislocation, but the dislocation was dominant. The progressive failure of bolts and waterproofing measures were also revealed. The evaluation of structural integrity of circumferential joint and the mitigate measures were proposed in order to ensure the operational safety of a metro tunnel.(4) The deformation characteristics of tunnel lining and joints under the concentrated load were analyzed. Protection measures such as reinforced frames aroundceiling segments and a change in the location of the bolts at the crown were suggested to reduce dislocations of joints and force of bolts. |
