Investigation of the structural effect induced by stagger joints in segmental tunnel linings: First results from full-scale ring tests

摘要

It has been found that in the operation of shield tunnels in urban rail traffic system, different assembling segmental tunnel structures demonstrate distinct service qualities. There is still controversy among engineers and scientists regarding the influence of circumferential joints on the overall structural mechanical behavior. This study designed and performed full-scale experiments relating to the structural bearing capacity of stagger joint assembled shield tunnels based on an unloading situation, which combines engineering practices relevant to the current urban metro with circumferential disturbances. The design of tested linings and loading schemes are described. The most important results include the evolution of deformations, structural internal force, and behavior of both the longitudinal and circumferential joints. The failure mechanism of the tested linings is analyzed. The performance of different jointed segmental tunnel linings is further compared. Via the experimental investigation, the structural effect induced by stagger joints in segmental tunnel linings is quantitatively highlighted. And the progressive failure and ultimate capacity of staggered segmental linings are captured under the designed loading situation. It is concluded that circumferential joints of segmental tunnel linings should be designed in order to obtain the deemed structural-unity. What's more, the difference in mechanical behavior is clarified through the performance comparison of different jointed segmental tunnel linings, which offers direct evidences for the serviceability assessment of operated metro tunnels.