Shield method is widely used in tunnel construction due to its high construction speed, high economic efficiency and good safety characteristics, and the application of communication channels will also become increasingly widespread. However, the research for small-diameter shield tunnel stiffness efficiency is relatively limited. Based on a shield method contact channel project in Tianjin, with ABAQUS to establish a variety of tunnel and segment numerical calculation model, study the size of small diameter tunnel stiffness efficiency and influencing factors. The study found that: (1) The stiffness efficiency of the contact channel is not different from that of ordinary tunnel, the longitudinal stiffness efficiency is around 0.07, the transverse stiffness efficiency is between 0.5 and 0.6, the transverse stiffness improvement has a positive relationship on the longitudinal stiffness; (2) The segment assembly method has little influence on the efficiency of longitudinal stiffness, and extremely asymmetric deformation under the joint assembly; (3) The tension of the bolt, which has some influence on the efficiency of the longitudinal stiffness, but has little influence on the efficiency of transverse stiffness.

In order to overcome the long distance difficulties of construction in the construction of the traditional freezing method and the influence of freezing, swelling and subsidence, based on the shield method contact channel of Tianjin Metro Line 10, the technical points and control methods of shield method construction of long-distance contact channel in Tianjin, as well as the influence on the surrounding environment, are analyzed and studied. The results show that: In the soft soil area of Tianjin, using measures such as the closed sleeve, micro-freezing reinforcement, steel plate ring beam, grouting plugging and reinforcement measures at the starting and receiving ends of the contact channel can strictly control and timely adjust the shield tunneling parameters, which can effectively prevent the risk of water leakage and sand leakage and reduce the impact on the main tunnel and the surrounding environment. The shield construction of the contact channel will lead to U-shaped settlement deformation of the upper soil along the tunnel axis direction. The settlement of the starting end is generally greater than the settlement of the receiving end, and the maximum settlement is about 10mm, which has little overall impact on the construction (structure). As the carrier of construction force in the main tunnel, the horizontal displacement of the main tunnel at the starting end is greater than that of the receiving end. The initial tunnel will present the convergent deformation of the horizontal ellipse and then the vertical ellipse, so the main tunnel at the initial section should be focused on.

The hexagonal tunnel has the advantages of better deformation and mechanical performance, and the space utilization ratio is better than that of the circular tunnel. But it’s still a lack of research on the performance comparison and corresponding design parameters under different types of assembly forms. In order to explorer the performances of the transverse effective rigidity ratio of the hexagonal tunnel, stagger-jointed, straight-jointed and uniform models are investigated based on model tests and similarity theories. The experiment results are verified by numerical simulation. On this basis, numerical models are used to further study the bending moment distribution of the three models, and the bending moment transferring coefficient of stagger-jointed structure is calculated. The results show that: The transverse effective rigidity ratio is between 0.85 and 0.89 under stagger-jointed condition, and significantly better than that between 0.62 and 0.68 under straight-jointed condition. The bending moment distribution and bending moment transferring coefficient of staggered joint structure change periodically. The bending moment transferring coefficient is between 0.18 and 0.36. The results can be used as a reference for the design of hexagonal tunnel.