Bending strain and displacement monitoring method for pipelines in permafrost zones

The pipelines in permafrost zones are prone to displacement and deformation due to the effect of geologic disasters (e.g. thaw settlement and frozen swelling). In order to deal with this problem, a high-precision inertial navigation system was developed to perform internal inspection on pipelines, so as to acquire the position and attitude information of detectors. And based on this, the pipeline bending strain and displacement calculation methods were developed. When the pipeline displacement is calculated, a method to correct errors by using external characteristic points is proposed to deal with the divergence of pipeline calculation trajectory. When the variation of pipeline displacement or bending strain is calculated, it is proposed to do the comparison after the data of pipelines with fixed length is aligned, so that the mileage difference of repeated testing can be eliminated. The feasibility and inspection precision of this system and method are verified through the field application. It provides the scientific basis for pipeline accident prevention and reasonable maintenance. And it is of actual significance to the safe operation of long-distance oil and gas pipelines in permafrost zones.