Transport Phenomena in Frozen Porous Media: Fid-Bau Portal

Transport Phenomena in Frozen Porous Media

Perfect, E. / Groenevelt, P. H. / Kay, B. D.

Abstract Processes associated with heat and mass transport in porous media at sub-zero temperatures are reviewed within the framework of non-equilibrium thermodynamics. Frozen porous media are considered to be made up of heat, water (in the liquid and solid states), solutes, charge and the soil matrix. Relations between these components are considered under static conditions. It is assumed that the principal of microscopic reversibility can be applied. This provides a basis for the subsequent description of the dynamics of heat and mass transfer in a frozen, non-heaving soil. A general expression is given for the energy dissipation in this system. Flux equations are then derived for each component in terms of direct and coupled driving forces. Direct transport of a component arises from a gradient in some property of that component Coupled transport occurs when flow of one component arises from a gradient in some property of another component. The theoretical relations are compared with published examples of direct and coupled transport in frozen porous media. Transport of the soil matrix caused by the accumulation of water as ice (i.e. frost heave) is discussed. Several recent frost heave models are examined. A non-equilibrium thermodynamic treatment of this phenomenon is not attempted. However, the methodology is in place and deserves further investigation. Additional recommendations for future research include: testing the assumption of microscopic reversibility, development of methods to measure liquid and ice pressures in pores, determination of the transport coefficients associated with electro-kinetic phenomena, adaption of existing theories to structured and colloidal soils, and clarification of the mechanism of ice segregation behind the warmest zone of lensing.