Experimental study of freezing infiltration through a layered porous medium

Gravity-driven infiltration through porous media has been well studied in the context of soil hydrology. Recently, the problem has received renewed attention in cold-region hydrology, where the infiltration of water through snow, firn and permafrost are poorly understood but critical to understanding the response of these geosystems to climate change. Different from the isothermal scenario, infiltration through subfreezing porous media is complicated due to the additional heat transfer and freezing processes that locally modify permeability and deplete fluid saturation.

In this work, we experimentally investigate the infiltration of a single flow channel through a subfreezing, two-layered porous medium. The choice of a layered structure is to mimic that of natural snow or permafrost, which are often texturally stratified such that flow can be diverted horizontally from capillary barriers or by a sharp decline in permeability. A rectangular Hele-Shaw cell is packed with two horizontal layers of glass beads of different sizes and housed within a temperature-controlled chamber that maintains a subfreezing air temperature. We then inject 0 ºC water dyed with fluorescein salt which allows us to distinguish between the liquid and ice phase. By varying the injection flow rate, chamber temperature, and grain size, we present a phase diagram of freezing infiltration for a single channel and identify regions in the parameter space where freezing out competes flow to arrest infiltration completely.