Method for detection of deformation stress of large-diameter and high-pressure pipeline under complex terrain

China-Russia Eastern Gas Pipeline is characterized by ultra-large diameter, high grade steel (X80) and high pressure rating. It is located in the area with geologically active permafrost and semi-permafrost zones in the north, where is prone to geological disasters. Hence, the non-design load may bring about the overall stress level of the pipeline exceeding the strain capacity of the pipeline, which poses great challenges to the structural integrity and long-term safe operation of the pipeline. Therefore, high-precision measurement of stress value during pipeline operation will be crucial to its safety assessment. According to the actual service conditions of China-Russia Eastern Gas Pipeline, the propagation time of ultrasonic LCR wave in the elastic-plastic deformation of X80 steel was measured, and the propagation rule of ultrasonic LCR wave in the elastic deformation and plastic deformation of X80 steel was explored on the basis of studying the theory and method of detecting pipeline stress by ultrasonic LCR wave. At the initial operation stage of China-Russia Eastern Gas Pipeline, the reliable and applicable pipeline stress measurement technology was formed, serving as a technical reserve for the future safety assessment of the pipeline in its operation and maintenance.