Vertical upheaval buckling is a critical instability mode in buried pipelines and poses substantial risks to pipeline safety. Most prior studies have focused on upheaval behavior under flat terrain

with limited attention to failure mechanisms on slopes. In this study

model tests of buried-pipeline upheaval on slopes were conducted using distributed fiber-optic sensing and particle image velocimetry (PIV). We systematically analyzed soil deformation and failure mechanisms

and the mobilization of uplift resistance

under varying slope angles and burial-depth ratios. The results show that

1) Increasing slope angle gradually reduces the soil’s peak uplift resistance

while higher burial-depth ratios significantly enhance both peak and residual uplift resistances. 2) Regardless of slope angle or burial depth

the pipeline displacement at the onset of residual resistance is approximately 0.2

where is the pipe outer diameter. 3) During the uplift process

the pipe cross-section undergoes ovalization

and a wedge-shaped failure zone forms in the overlying soil. Based on these findings and Mohr’s circle theory

we propose a method to calculate the peak soil resistance of pipelines under slope conditions. These findings advance understanding of soil–pipeline interaction on sloped terrain and provide theoretical and practical guidance for the design and safety assessment of buried pipelines in complex geological settings.