The influence of interfacial joints on the structural behavior of segmental tunnel rings subjected to ground pressure

Abstract

The local behavior of segment-to-segment interfaces has a significant influence on the overall structural behavior of segmental tunnel rings subjected to ground pressure. This is quantified by means of structural simulations, combining analytical solutions of the linear theory of slender circular arches with time-dependent and nonlinear interface models for unreinforced and bolted interfaces. The time-dependent behavior results from creep of concrete and the nonlinear behavior from interfacial separation, crushing of concrete, and yielding of steel. Structural sensitivity analyses are performed with respect to the coefficient of lateral ground pressure. The influence of creep of concrete at unreinforced interfaces on the overall structural behavior is demonstrated, based on the interface models by Gladwell and Janßen. Furthermore, the elastic limits and the bearing capacities of segmental tunnel rings are quantified both for unreinforced and bolted interfaces. The corresponding interface law is based on the Bernoulli-Euler hypothesis and on linear-elastic and ideal-plastic behavior of both concrete and steel. In order to underline the reliability of the computed bearing capacities, a bearing-capacity test on a real-scale segmental tunnel ring is re-analyzed. It is concluded that (i) creep of concrete at the interfaces results in an increase of the structural displacements, while the distributions of the inner forces remain practically the same, (ii) interfacial bolts improve the serviceability of segmental tunnel rings, because they ensure the position stability of the lining, and (iii) the bearing capacity of segmental tunnel rings subjected to ground pressure can be estimated reliably, based on the combination of realistic interface models and analytical solutions of the linear theory of slender circular arches.