Study On The Structural Model With Characteristics Of Large Shield Tunnel

As an effective measure to mitigate the dilemma between the limitation of overground spaces and the heavy load of transportation, large shield tunnels become important underground structures in urban area owing to the breakthroughs in construction technology. Compared with the quick development in practical engineering, the theoretical research in structural model for large shield tunnels is relative delayed. Currently, those designing methods for small shield tunnels are simply applied when designing large tunnels. Considering the structural specialties in large shield tunnels, a detail study on the designing method for large shield tunnels is presented in this thesis.A summary about current designing methods for shield tunnel is present at first, then a comparison between the uniform rigidity ring model, the elastic multi-hinge model and the two-ring of beam-spring model is conducted via calculations, which take into account the influence of the stiffness of joints.With the construction of large shield tunnels, some trends and characteristics, i.e. more segments in a ring, the diversity of stagger angle and the increasing numbers of longitudinal joints, are shown in design. The thesis has explored the impact of above factors on the internal forces in tunnel lining.Usually, tunnels are easy to bury shallowly for the reason of the large section, thus an analytical solution based on Force Method is presented in this paper, taking account of the change in the distribution of soil resistant pressure, and then an analysis of parameters are made, considering influencing factors for the distribution of soil resistant pressure, i.e. horizontal soil pressure coefficient, soil resistant coefficient, and buried depth. The analysis verifies that these factors indeed have some effect on either the location or the range of the distribution of the soil resistant pressure. And the impact for large shield tunnels is more obvious then that in smaller shield tunnels.In terms of the influence of self-weight of tunnel lining on the calculation of soil...