Several key problems in tunnel construction monitoring with FBG

Fiber Bragg grating (FBG) sensor has a number of advantages such as high sensitivity, multiplexing capabilities, fast response, resistance to corrosion, and immunity to electromagnetic noise and radio frequency interference, and has been widely applied in engineering monitoring. The environment of tunnel construction site is usually very severe and harsh, whereas the unprotected FBG sensor is very vulnerable and sensitive to its surroundings. Therefore there are still some key problems to be solved when the FBG sensor is used in tunnel construction monitoring. Some key problems such as the protection of FBG sensor, temperature compensation and monitoring system integration for tunnel construction are discussed and analyzed through a practical engineering case. It is indicate that the survival rate of FBG sensor can be greatly raised via proper sealing and protection, and the real-time monitoring for the strain and stress of the arch and supporting bar and temperature of tunnel structure during the blasting excavating and concrete spraying of tunnel is feasible.