Heat and mass transfer in frozen porous media

In this thesis processes and parameters associated with heat and mass transfer in frozen porous media both on a theoretical and empirical basis are studied. To obtain the required measurements some existing measuring methods needed to be improved.

Firstly, an improved model has been developed for the measurement of thermal conductivity with use of the nonsteady-state probe method. The measurements of thermal conductivity indicate four separate effects caused by the freezing process.

The second improved measuring method is the measurement of bulk electrical conductivity with use of time-domain reflectometry.

And the third improvement is the use of the dispersion theory in the description of relations between water content and bulk electrical conductivity or dielectric constant.

This thesis shows that time-domain reflectometry can be used to measure the unfrozen water content and bulk electrical conductivity simultaneously under frozen conditions and that from the latter parameter solute redistribution can be monitored.

From the measured heat flows a time delay in the forming of pore ice can be concluded. From the measured moisture transport (resulting in frost heave) a relation with some soil properties could be established. For some of the materials studied a minimum temperature gradient has been observed atwhichheave starts. From this and other results an effort was made to come to a synthesis of the rigid ice concept and the segregation potential concept.

The thesis finishes with some recommandations in connection with the improvement of soil structure by freezing, frost heave and artificial ground freezing.