Developing and Utilizing a Universal Model for the Study of Slope Stability under Freeze–Thaw Action in the Presence of an Oil Pipeline Crossing

Pipeline crossings influence the soil water and heat distribution and then affect soil shear strength parameters, including internal friction angle and cohesion. Soil melting reduces the shear strength. Slope instability, which could lead to pipeline exposure, deformation, and so on, may occur under rainfall and soil gravity. Thus the stability of permafrost slopes with a pipeline crossing was studied. The safe slope angle that the pipeline could cross without protective measures was determined. Based on the strength reduction method and Drucker-Prager elastoplastic model, a universal finite-element model of slope and pipeline was established. The effects of water content and slope angle on the stability of permafrost slope were studied. The results show that March and April are the most stable months of the year, whereas September and October are the most dangerous months. The slope angle significantly influences the permafrost slope stability; the slope angle must be lower than 30°, and protective measures are necessary when the slope is greater than 30°. The increase of water content decreases the slope stability.