Understanding the longitudinal performance of shield tunnel from settlement to joint behavior by a novel physical modeling system

Apart from the settlement trough, the joint behavior in terms of dislocation and opening plays a pivotal role in determining the longitudinal performance of shield tunnel, while they have been less tackled neither on the site nor in the scaled test system. This paper proposes a novel physical modeling system with the emphasis on capturing both the longitudinal settlement trough and circumferential joint behavior of shield tunnel in one test. The test results have been compared with field data, exhibiting similar trends and magnitudes of change. Utilizing this newly proposed test system, relationship between joint dislocation and opening under differential settlement trough is closely revisited and the proportion of these two joint behaviors could be revealed as the responses to the maximum settlement of the troughs. Results show that the development of dislocation between rings is more prominent than joint opening at a small level of settlement and a higher proportion of joint opening would occur as the settlement increases. Besides, a modest linear correlation between the differential settlement and joint dislocation is observed, whereas no clear correlation is evident between the differential settlement and joint opening. Additionally, the paper discusses the adjustments for sensor position when utilizing this system to measure the tunnel heave or radial joint deformation. Overall, the good working performance and high measuring accuracy of the physical modeling system can enable more precise evaluations of tunnel deformation and refined structural behavior under various conditions.