Deformation mechanism and mechanical behavior of tunnel within contact zone: a case study

During the construction of a tunnel passing through a contact zone stratum, the supporting structure is at risk of large deformation, cracking, and collapse, which affects the safety of tunnel construction. Based on the Jiayuan Tunnel project, this study used field monitoring data and numerical simulation to conduct a case study on the support mechanism and deformation of the supporting structure of a tunnel passing through the contact zone stratum. The results obtained for four monitoring sections reveal that the supporting structure under the contact zone stratum receives more surrounding rock pressure compared with the general stratum. In this case, the stress and deformation of the supporting structure are larger. Moreover, the deformation and mechanical behavior were uneven at different parts of the supporting structure. Using the numerical software FLAC3D, the deformation mechanism and mechanical behavior of the supporting structure were analyzed and are related to the surrounding rock parameters and interface location. Combined with the feature of the supporting structure in the contact zone stratum, the supporting structure should be strengthened to avoid stress concentration, while the steel arch foot should receive more attention when the interface coincides with the step surface.