Damage assessment of a RC tunnel structure showing delaminations

In a long railway tunnel delaminations had been detected just after construction located near the inner reinforcement and aligning parallel to the surface. This paper presents the strategy to assess the damage in three steps: First the site documents were analysed to determine the cause of these delaminations, secondly a working hypothesis was formulated, what kind of deterioration mechanism may caused the delaminations, finally an investigation strategy was developed to verify/confirm the working hypothesis, petrographic analysis, impact-echo method. As mentioned, one integral part of the investigation was the employment of the non-destructive method impact-echo. The understanding of the impact-echo method and beforehand collected knowledge about the structure being tested (petrographic analysis) were both essential for successful field work. Finally, taking all beforehand collected information into account, an appropriate repair method was identified.