Strain monitoring of crossing-fault pipelines with coaxial cable FabryPerot interferometer sensors

Affected by the extreme geological hazards such as the fault and uneven ground settlement, pipelines are prone to produce large deformations. However, the large strain monitoring cannot be achieved with the existing strain sensing technology due to its insufficient measuring range. Thus, the method of monitoring the large strain of crossing-fault pipelines with Coaxial Cable Fabry-Perot Interferometer (CCFPI) sensors was proposed herein. Definitely, the sensing principle and manufacturing method of CCFPI sensors were briefly introduced, and with the help of a self-made buried crossing-fault pipeline test device, the packaging and deployment methods of CCFPI sensors to match the buried pipelines were studied.Additionally, the rationality and effectiveness of applying CCFPI sensors to the large strain monitoring of buried crossingfault pipelines was verified through the simulation test. The research results show that the measured strain value of the CCFPI sensor and the optical fiber sensor agrees well when the fault displacement is less than 165 mm. However, when the fault displacement is greater than 165 mm, the fiber breaks due to out-of-range, but the CCFPI sensor can monitor the strain of the pipeline continuously, and a strain of 0.081 36 is measured by the CCFPI sensor at a fault displacement of 300 mm, which verifies the rationality and reliability of applying the CCFPI sensors to large strain monitoring of buried crossing-fault pipelines.