Innovative methodology for advanced structural condition assessment of tunnels

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Parasyris, A. and Bairaktaris, D.; Anagnostou, Georgios and Benardos, Andreas and Marinos, Vassilis P., eds. (2023) Innovative methodology for advanced structural condition assessment of tunnels. In: Expanding Underground - Knowledge and Passion to Make a Positive Impact on the World. Expanding Underground - Knowledge and Passion to Make a Positive Impact on the World- Proceedings of the ITA-AITES World Tunnel Congress, WTC 2023 . CRC Press/Balkema, GRC, pp. 2493-2500. ISBN 9781003348030 (https://doi.org/10.1201/9781003348030-300)

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Abstract

A methodology for holistic structural condition assessment of tunnels through high technological monitoring tools is proposed in this article. The methodology is divided into structural evaluation in real time through pre-installed equipment at the construction phase, and to post event structural evaluation through robotic inspection. The first part focuses on the static evaluation of the permanent tunnel lining after a strong earthquake in real time through fiber optic measurements. For this purpose, an improved type of fiber optic sensors is used, installed on inner and outer transversal reinforcing bars at eight points along the perimeter, allowing the recording of the time history of the elongation developed during the seismic action. A reformulation of the Parc-Ang criterion has been developed, allowing accurate automatic estimation of the degree of damage in each critical section according to the Moment-curvature diagram and the overall degree of indeterminacy of the structure. In the second part, the innovative model for crack analysis is described extensively, through which it is possible to calculate internal forces at the position of the structure where the crack is occurred, but also to estimate the possible locations of invisible cracks in the back face, based on the measurement of cracks’ geometrical characteristics (widths, depths, angles and spacings) with sensors placed in robotic tools. Soil pressures and the internal forces N, V, M along the perimeter of the tunnel cross-section are calculated based on convergence measurements along 5 cords. The appropriateness of the methodology has been validated through the European Research Programs Tunneling, Monico, Robospect and Resist while the numerical results presented in this paper are obtained by application of robotic measurements in autonomous software packages implemented in JAVA programming language.

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