Experimental and numerical investigation on the cross-sectional mechanical behavior of prefabricated multi-cabin RC utility tunnels

Abstract

Prefabricated multi-cabin utility tunnels have been increasingly adopted in modern city underground lifeline structures to accommodate the soaring demands for a variety of lifeline pipelines and to avoid congestion. According to the reconnaissance reports of past major earthquakes, these tunnels are vulnerable to three different types of deformations during earthquake action: axial compression and tension, longitudinal bending, and racking/ovaling. Compared with first two types of deformations, the cross-sectional mechanical performance of multi-cabin utility tunnels under the racking deformation has rarely been studied. To bridge this knowledge gap, quasi-static experimental and numerical studies were conducted in this paper to investigate the cross-sectional mechanical behavior of prefabricated multi-cabin utility tunnels for lifeline pipelines under the free-field racking deformation. The experiment was conducted at both the component joint and global levels. To be specific, a ½-scale L-joint and T-joint specimen, and a ¼-scale global specimen of a prefabricated multi-cabin utility tunnel section were designed. All specimens were tested under a combination of a constant axial load and cyclic lateral loads to impose the racking deformation to the cross-section of tunnel. The test results indicated that under the racking deformation, the L-joint was more vulnerable than the T-joint and the cross-sectional performance of the prefabricated multi-cabin utility tunnels would be dominated by the exterior walls. It is likely that the prefabricated multi-cabin utility tunnels will retain integrity under the free-field racking deformation of ground while suffer local failure to the exterior walls under the free-racking deformation. The test results were then employed to validate the numerical models. Moreover, good agreement was obtained between the numerical and experimental results, giving confidence in current numerical modeling techniques for prefabricated multi-cabin utility tunnels.