Engineered Water Repellency for Frost Mitigation: Practical Modeling Considerations

Engineered water repellency has the potential to mitigate frost heave in geotechnical systems such as roads and foundations. Models can be used to inform design approaches and predict performance; the literature is replete with general models of frost action. There are comparatively fewer reports on how to practically incorporate the effect of mineral surfaces, pore fluid composition, and engineered water repellency into thermo-hydro-mechanical-chemical (THMC) models. An aspect of such models involves describing the state of pore fluid in the frozen fringe and unfrozen soil beneath an impinging freezing front and growing ice lens. Capillary and osmotic gradients are created as ice formation reduces moisture content while increasing the concentration of ions in the remaining unfrozen pore fluid. The work reported here is part of a larger effort to quantify the relative role of osmotic and matric potential on frost heaving, while exploring the use of organosilanes to mitigate ice lens formation and growth. As a precursor to incorporating the broader array of physicochemical processes in frost action, this paper reviews the sensitivity of unsaturated flow to changes in contact angle. Unsaturated flow gradients are created in response to simulated matric, osmotic, and cryogenic suction within a two-dimensional model. Results indicate that an increased contact angle results in a reduction in unsaturated flow, regardless of induced gradient.