Load Transfer in Tunnel Segments: A Contribution to Emphasize the Importance of the Load Introduction System in Experimental Testing

Abstract

In modern tunnel construction with continuous tunnel boring, the use of segmental lining is an important method of economically shaping the load-bearing tunnel lining. As the lining consists of numerous, separate tunnel segments, the design of the joints calls for special care in terms of the load transfer and load-bearing capacity of the whole tunnel segment, respectively. The longitudinal joint is characterized by a reduced cross section to ensure adequate installation and durability of the tunnel segments. Accordingly, the longitudinal joint is commonly decisive for the design of the tunnel segment and, therefore, subject of ongoing research. The Institute of Structural Engineering at TU Wien developed a novel reinforcement concept improving the load transfer in the longitudinal joint by using butt-jointed reinforcement. The application of the concept has been tested successfully in large-scale tests, where identical specimens were pressed against each other, as it is the case for real tunnel segments. However, as this constitutes an elaborate test setup, the evaluation of its necessity is of great interest for future experiments. Therefore, tests on cylindrical specimens have been conducted to quantify the influence of load introduction with steel plates compared to concrete-to-concrete interaction. This paper briefly summarizes the reinforcement concept of the TU Wien and presents the results of the experiments on the load introduction systems.