# Safety Analysis and Condition Assessment of Corroded Energy Pipelines under Landslide Disasters
## 4 Results and Discussion
### Effect of Corrosion Location
As this distance increases, the impact of corrosion on pipeline safety gradually diminishes. As shown in Figure 16, under a displacement ranging from 0 to 1 m, the equivalent stress is the largest and the fastest growing when the corrosion defect is at the center of the landslide. Upon reaching the yield state, the stress stabilizes. For defects between 0 and 5.5 m, the growth rate consistently decreases, indicating that the weakening effect at the defect site surpasses the landslide impact at the center. However, when the pipeline defect lies between 6.5 and 12.5 m, there is a distinct segmented effect in the stress curve. That is, once the displacement reaches a specific value, the stress escalates at a faster rate until it hits the yield strength. Because with low landslide load, the maximum stress is at the corrosion defect away from the landslide center. As the load increases, stress at the landslide center sharply rises. After a certain point, stress growth aligns closely until yielding. Thus, for a corrosion distance of 5.5 m from the landslide center, the focus is on the safety impact of corrosion. Beyond 6.5 m, we prioritize the effect of landslide displacement on central pipeline safety. Figure 14: Stress distribution and limit displacement: (**a**) circumferential stress distribution at 0.8 m displacement across different corrosion positions; and (**b**) limit displacement for various corrosion locations. Figure 15: Stress distribution cloud diagrams at different axial positions: (**a**) 0.5 m from pipeline center with corrosion; (**b**) 6 m from pipeline center with corrosion; (**c**) 6.5 m from pipeline center with corrosion; and (**d**) 12.5 m from pipeline center with corrosion. To further validate the conclusions, an analysis was conducted for corrosion distances of 0 m, 3.5 m, 7.5 m, and 10.5 m from the pipeline center, as shown in Figure 17. With increasing landslide loads for distances of 0.5 m and 3.5 m, the stress in the landslide and adjacent areas rises, concentrating at the corrosion site, resulting in pipe failure and reaching its yield strength, and the most critical point remains at the corrosion location. For distances of 7.5 m, the maximum stress shifts from the corrosion site to the center of the landslide, and the disparity between them widens with increasing displacement. Figure 16: Stress variation for different axial corrosion positions in the pipeline. Figure 10:0 Axial stress distribution in the pipeline with displacement at typical corrosion locations: (**a**) corrosion at the pipeline center; (**b**) corrosion 3.5 m from the center; (**c**) corrosion 7.5 m from the center; and (**d**) corrosion 10.5 m from the center. For a displacement of 0.8 m, the axial stress distribution of pipelines both without corrosion and with corrosion ranging from 0 to 12.5 m is extracted. As shown in Figure 18, aside from the abrupt change in the corrosion defect, the axial stress distributions across all scenarios are largely consistent, displaying a tri-peak profile. When the corrosion is within 3.5 m from the center, the stress at the corroded spot exceeds the minimum yield stress with minor abrupt changes. Beyond 3.5 m, the pipeline has not yielded, but defects within 5.5 m exceed the allowable stress, failing with a relatively significant stress change at the corrosion site. The stress at the corrosion defect decreases axially but shows a slight increase between 10.5 m and 12.5 m. This is due to the decreasing distance to the landslide edge, where the edge shear combined with the corrosion defect intensify the stress on the pipeline at this location. Under the landslide influence, the most hazardous point on the pipeline is not necessarily the corrosion defect. In real-world conditions, evaluations should consider the landslide direction, displacement, and the axial and circumferential position of the corrosion. It is crucial to understand the relationship between corrosion sites and landslide-affected pipelines, pinpoint potential danger zones, and avoid over-protection.