Numerical Analysis of Pipeline Uplift Resistance in Frozen Clay Soil Considering Hybrid Tensile-Shear Yield Behaviors

Abstract

Pipeline uplift resistance plays an essential role in the design of buried pipelines in permafrost regions or artificially frozen ground. The uplift resistance of a frozen soil is dependent on the soil’s mechanical properties, which are needed to characterize plastic zones in the frozen soil that surrounds pipes. Owing to the presence of unfrozen water, frozen soils (especially frozen clay) display complex mechanical properties that vary with temperature. There are limited amount of research studies with a focus on frozen soil–pipe interactions that consider temperature change within the literature. In this study, numerical modeling is conducted to investigate frozen soil–pipe interactions at different temperatures. A pipe is simulated with vertical displacement-controlled or vertical load-controlled conditions. The temperature-dependent mechanical parameters of frozen clay soil are examined in the simulation. Both tensile yield and shear yield behaviors are included in the modeling with the consideration of temperature-dependent failure criterions. Simulated stress paths in monitoring points are collected and displayed. The results from the Mohr–Coulomb model with the Rankine tensile cut off, and the hyperbolic Drucker–Prager model are compared and analyzed. The results indicate that hyperbolic Drucker–Prager model is effective for analyzing soil plastic zones surrounding a pipe. The applied hyperbolic Drucker–Prager model with reduced strength parameters can produce a more conservative uplift resistance–displacement relation when compared with that from the Mohr–Coulomb model. Thermally induced plastic strain may have a significant impact on the uplift resistance analysis, since a significant thermally induced uplift displacement is expected if there is a heat transfer process from a buried pipe to the surrounding frozen soil.