Monitoring the Deformation of Pipelines During Soil Freeze-Thaw Cycle Using Distributed Fiber Sensor

The soil freeze-thaw process can lead buckling or even leakage of the buried pipeline. This paper presents experimental methods and results to describe the deformation of oil and natural gas pipeline during the soil freeze-thaw process using distributed fiber sensor. The test box for simulating soil freeze-thaw cycle and test pipeline were produced. Two distributed fiber sensors were attached to the test pipeline. A FBG temperature sensor was fixed inside the test pipeline. The test pipeline was first placed in the box and then covered by saturated soil. A LUNA-A distributed fiber sensing system and a FBG demodulator were monitored deformation and temperature change of the pipeline during the soil freeze-thaw transition, respectively. The strain data collected at the LUNA-A are utilized to quantitatively describe the deformation of the pipeline. The alteration of the deformation of the pipeline during the soil freeze-thaw process has an important effect on the strain data. Potentially, distributed fiber sensor solves the problem that the quasi-distributed FBG sensor cannot monitor the whole deformation of the pipeline, which is a promising sensor in pipeline safety monitoring.