Factors Affecting Frost Heave of Chilled Gas Pipelines

Chilled gas pipelines generally traverse a long distance through various soils and may operate for decades with varying temperatures of gas, surrounding soil, and ground surface. The present study investigates the effects of key factors on frost heave using two-dimensional finite-element modeling of the coupled thermomechanical process by implementing the Konrad-Morgenstern segregation potential model. A simplified approach is proposed to estimate the thaw-back effects on long-term frost heave. The seasonal variation of ground surface temperature significantly affects the heave, especially for pipelines at shallow burial depths and for long-term heaving. An increase in cohesion of the frozen soil and a reduction in the initial ground temperature reduce the heave. Modeling of frozen fringe and stress effects on segregation potential are discussed. Subzero gas temperature has a smaller effect on heave for lower initial ground temperatures; however, it significantly affects long-term heave for higher ground temperatures.