Thermally induced heave beneath chilled pipelines in frozen ground

Abstract

Thermally induced water migration beneath chilled structures in frozen ground near its melting point has been considered by some as a possible source of heave and structural distress. This paper analyses the two-dimensional problem of thermally induced water flow in frozen soils beneath a chilled buried pipe, both for steady state and early transient conditions. The analysis has identified the primary variables of interest in the problem of thermally induced heave in frozen ground, and by omitting some second-order effects has obtained a relatively straightforward relationship for the steady state heave rate due to this process. Using published relationships for hydraulic conductivity of frozen soils, it is concluded that heave induced by this mechanism will be relatively minor, and should not result in significant pipe bending or structural distress in the long term. Initial transient and seasonal effects were studied using the same govering equation for fluid flow, coupled with the author's two-dimensional thermal simulator. Additional heave due to these effects does not appear to increase the overall predicted heave greatly. Key words: heave, water flow in frozen soil, pipeline, frozen soil, permeability.