Pore water pressure evolution below a freezing front under saturated conditions: Large-scale laboratory experiment and numerical investigation

• Published in: Cold regions science and technology 2019-02, Vol.158, p.76-94
• Main Authors: Rivière, Agnès, Jost, Anne, Gonçalvès, Julio, Font, Marianne
• Format: Article
• Language: English
• Subjects: Bioclimatology; Biodiversity and Ecology; Business administration; Climatology; Continental interfaces, environment; Earth Sciences; Ecology, environment; Ecosystems; Engineering Sciences; Environment and Society; Environmental Engineering; Environmental Sciences; Environmental studies; Excess pore-water pressure; Fluid Dynamics; Freeze-thaw cycle; Frost heave; Geochemistry; Global Changes; Humanities and Social Sciences; Hydrology; Ice expansion; Large-scale laboratory experiment; Life Sciences; Mechanics; Numerical simulations; Physics; Reactive fluid environment; Sciences of the Universe; Subpermafrost aquifer; Thermics
• ISSN: 0165-232X; 1872-7441
• DOI: 10.1016/j.coldregions.2018.11.005

Subpermafrost aquifer hydrodynamics is generally poorly known due to monitoring technology issues. The few available data show that this aquifer is confined below continuous permafrost due to ice expansion. We conducted a 2 m × 1 m × 1 m sand box experiment under controlled conditions in a cold room to (1) evaluate the confinement of the unfrozen part of a saturated porous medium below a propagating freezing/thawing front, (2) assess the associated uplift of the soil surface, and therefore (3) quantify how the ice expansion translates into frost heave and excess pore-water pressure in the unfrozen part below the freezing soil. Pore water pressure, soil temperature and soil heave were monitored inside the sand box during a 70-day freeze-thaw cycle. A transient fully coupled heat transport and water flow model (called Ginette) was developed to reproduce the freeze-thaw experiment numerically. It takes into account excess pore-water pressure related to pore water phase changes and uses a simple hydro-mechanical term based on the storage coefficient to estimate soil heave. Fairly good agreement was obtained between measured and simulated pressure heads in the unfrozen part below the freezing front over time. Both experimental and numerical approaches show that the ice expansion is translated into excess pore-water pressure (maximum pore water pressure: 5.5 m) and frost heave (2.2 cm). [Display omitted] •Quantifying the impact of the ice expansion during a freezing/thawing cycle•Experimental data set for the development and validation of numerical codes•Hydrologeological conceptualisation of the pore water pressure evolution•Confirmation of the confinement of subpermafrost aquifer•Crucial role of the porosity and the storage coefficient