Mechanical behaviour of segmental lining of a sub-rectangular shield tunnel under self-weight

In this paper, a novel loading setup was developed for performing full-scale loading tests on 'standing' segmental lining of a sub-rectangular shield tunnel, which for the first time allows the mechanical behaviour of segmental lining subject to self-weight to be assessed in a full-scale loading test. Granular rubber bearings with an equivalent coefficient of subgrade reaction close to hard plastic clay were used to simulate subgrade soils. The experimental results showed that the internal force distribution and deformation pattern of lining ring subject to self-weight loading differed significantly from that observed in a 'lying' loading test considering soil-and-water pressures due to the absence of lateral confinement and different boundary conditions. Specifically, maximum positive bending moments were observed at the crown and invert regions, and the largest negative bending moments occurred at the two waists. Stress concentration was not observed at the corners. The axial force was not universally compressive with tensile axial forces present at the crown region. Furthermore, the convergence deformation under self-weight loading was non-negligible. The overall lateral expansion deformation was close to the vertical convergence deformation, but the deformation was smaller at the invert than that at the crown. It is suggested that the influence of self-weight be considered in future full-scale loading tests, especially for shallowly-buried tunnels.