Failure mechanism of the full-ring for segmented tunnel lining

To study the failure mechanism of segmented tunnel lining in the ultimate limit state, 3-rings full-scale tests on a segmented tunnel are performed by applying ovalisation load, and the failure history is analyzed by means of the parameters of failure index of segments and segment joints. The results show that the load bearing state and failure possibility of the component of the tunnel can be traced effectively, and the failure history can be described and explained according to the two parameters. The prediction of the crack and crush of the test tunnel rings can be verified by the observed and measured data obtained from the prototype tests. The failure history of the segment tunnel lining is composed of the crack initiation of segment joints, crack initiation of segments, formation of plastic hinge in segments, yielding of segment joints, development of multiple plastic hinges in segments and loss of the load bearing capacity of the whole rings. The initiation location and development sequence of plastic hinge in segments are influenced and controlled by the critical cross-sections in rings of the segmented tunnel lining.