Vertical Displacement Monitoring and Safety Evaluation of Oil Pipelines in Permafrost Region

This paper presents the development of a liquid pressure based automatic monitoring device of the vertical displacement of oil pipeline that has good applicability to the extreme cold conditions of the permafrost region and is capable of automatic collection and transmission of monitoring data. The effectiveness of the device has been verified using total station measurement method and the results show that the device can intuitively indicate the vertical displacement of the pipe under the harmful influence of frost heaving and thaw settlement. According to the monitoring data, safety evaluation of the pipe during the monitoring period is carried out using stress-based design criteria and strain-based design criteria respectively. The analytic results with stress-based design criteria show that the pipe may be in a dangerous state while the results with strain-based design criteria show that the pipe is in a safe state. The design method with strain-based criteria is complementary to the design method with stress-based criteria. Separate use of either method is not recommended.