Optimized reinforcement in longitudinal joints of segmental tunnel linings

Abstract

AbstractWhen building tunnels using segmental lining, the segmental lining takes over the supporting role of the excavated soil. With the workspace in tunnel construction being very constricted the circular, segmental linings are divided into small segments called tubbings which are assembled by a tunnel boring machine. This kind of construction results in numerous longitudinal and circumferential joints. The loading situation for the longitudinal joints is typically dominated by the compressive normal forces combined with relatively small bending moments. The thickness of the tubbings usually depends on the longitudinal joints of the individual segments. The cross‐sectional area of the tubbings has to be reduced at the joints in order to avoid spalling of the concrete leading to higher compression in the joints themselves. The Institute of Structural Engineering of TU Wien developed a new reinforcement design for tubbings with strengthened longitudinal joints. With a patent application pending, the newly designed joints were manufactured and tested demonstrating that the TU Wien proposal significantly increases the load‐bearing capacity of the tubbings in comparison to conventional tubbing solutions. The very satisfying results, obtained from the large‐scale tests of the newly developed joint design, show great potential for the construction of tunnels with thinner tubbings in the near future.