Abstract: Landslide is the main geological disaster that threatens the safe operation of natural gas pipelines. It is of great significance to investigate the analysis method that is suitable for the evolution law of landslide and the mechanical response of overburden pipes in engineering. Therefore, based on the principle of the minimum potential energy, the total potential energy balance equation of slope system (from anti-sliding section to sliding section), i.e., the Lagrange variational equation, was firstly adopted to obtain the critical conditions for the instability and slip of the slope. When the strain energy of the sliding section is equal to the strain energy for the crack and penetration of the anti-sliding section, the slope will slip. Meanwhile, the strain energy stored in the slope will be transformed into kinetic energy. On one hand, according to the contact relationship between the rock mass and the pipeline during the sliding process, the mechanical response model of the pipeline in two landslide stages is proposed. On the other hand, considering the fragmentation of the rock and soil mass, the uniform stress model of pipeline under the action of rock landslide and the non-uniform stress model of soil slope pipeline are proposed respectively. In view of this, based on the mechanical response for the small-scale interaction of the pipeline and soil, the stress expression of the pipeline in the pre- and post-sliding stages of rock and soil slopes, which is suitable in the elastic part, is derived. Finally, taking the EES244 section of natural gas pipeline from Sichuan to East as the research target, the total potential energy equation of the slope system is established, the situations for deformation, instability and slip of the slope are analyzed, the stress values of the pipeline in different sliding stages are calculated, and the safety of the pipeline is evaluated. Meanwhile, the stress analysis and the safety verification of the pipeline are carried out from a large-scale perspective by means of the numerical method. The results show that a sudden change of stress in the pipeline will be occurred near the interface between the sliding zone and the non-sliding zone, and the internal stress in the sliding zone increases slightly, while the whole pipeline is in a safe and stable state. Therefore, combining the small-scale theoretical calculation and the large-scale numerical method is of great significance and practical value, especially for the preliminary designing of the proposed pipeline, the safety evaluation of the existing pipeline and the later maintenance of the pipeline.

Key words: time-spatial revolution, anti-sliding section, overburden pipeline, total potential energy balance equation, scale