Exploring the three-dimensional response of a water storage and sewage tunnel based on full-scale loading tests

Abstract This paper investigated the three-dimensional effect through full-scale loading tests on both a single (isolated) full-ring structure and a staggered-fabricated three-ring structure for a water storage and sewage tunnel. Some observations common for both the single-ring and three-ring tests were identified: both the internal forces and deformation of the testing specimen increase as the burial depth increases; whereas, the axial force decreases but the deformation of the testing specimen increases with increasing inner water head. Comparing with the single-ring tests, the deformation of longitudinal joints and the convergence deformation of the testing specimen are significantly reduced in the three-ring tests. The reasons may be two-fold: firstly, the staggered fabrication causes the redistribution of bending moment in the longitudinal direction, which transfers a certain amount of bending moment from the longitudinal joints to the segment body of adjacent rings; secondly, the presence of thrust force leads to the closure of circumferential joints, which co-acting with the longitudinal bolts, enforces the joints to deform together with the segment body of adjacent rings and thus restricts the deformation of the longitudinal joints. It is also shown that the mechanism of bending moment transmission is not unique but depends on the loading conditions and joint locations.