Magnetic–Mechanical Response Mechanism and Quantitative Stress Characterization Method for Pipelines Under Lateral Landslide Loads
Mountainous landslides have become a major cause of failures and leaks in natural gas pipelines. However, effective monitoring technologies for determining the actual stress state and assessing the risk of cross-slope laying pipelines are still lacking. Therefore, this study establishes a fluid–structure interaction model for pipelines subjected to lateral landslide action, quantitatively investigating the characteristics of pipeline stress during landslide movement. Based on noncontact magnetic detection technology and integrated with a stress and magnetization relationship model of pipelines under complex loads established by experiments, a forward model for the magnetic–mechanical behavior of pipelines under lateral landslide action is established, quantitatively investigating the response mechanism between pipeline stress and magnetic gradient signals ( $G$ ) for cross-slope laying pipeline. Finally, the quantitative stress characterization model of pipelines based on the magnetic gradient signal is established. Results indicate that the maximum Mises stress reaches 70.92 % of the yield strength at the end of the landslide creep. The average growth rates of the maximum Mises stress with respect to the internal pressure, burial depth, and wall thickness of the pipeline are 5.11 %/MPa, 12.67 %/m, and −9.08 %/mm. The magnetic gradient signal exhibits a peak at the landslide centerline and demonstrates a positive exponential relationship with the maximum Mises stress, while three influencing factors solely affect the magnitude of $G$ . The quantitative stress characterization model of pipelines, calibrated using the signal conversion factor, exhibits a maximum error of 3.34 %. The self-developed noncontact magnetic monitoring device has been successfully applied in the field.