In this paper, we introduce a distributed fiber optic sensing approach for crack monitoring along concrete tunnel linings. The designed setup allows strain measurements with a very high precision of about 1µm/m every 10 millimeters or even better. Structural cracks may develop in the secondary lining due to this stress redistribution and bias pressure, consequently affecting the overall construction safety of the tunnel. This paper aims to achieve real-time monitoring of the excavation stability of the lining structure by integrating two. How HBK's advanced fibre optic sensing technology enabled real-time strain and temperature insights at the Kühtai 2 hydropower station. Fiber Bragg sensors measure physical quantities, such as strain, with light. The earth pressures involved in tunnel lining structural design has been determined based on experience.
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