Effect of freeze-thaw cycles on hydraulic properties of (Boom) clay

Cold climatic conditions as we have experienced in north-western Europe about 20.000 years ago are likely to return during the next 1 Ma. Permafrost (perennially frozen ground) might develop and although it is not very likely, the freezing front might reach the Boom Clay. In this report, a short overview is given on the possible consequences of freeze-thaw cycles on the hydraulic conductivity of clay sediments in general. In-situ and laboratory freeze-thaw tests indicate that after a few cycles, the hydraulic conductivity of the investigated clay samples (without overburden pressure) had increased by 2-3 orders of magnitude. Experiments with overburden pressure strongly suggest that the effect of freezing and thawing on the hydraulic conductivity of clay specimens is negligible as long as the burial depth is sufficient, i.e., at least several meters. Observations of hydraulic conductivity in a Boom Clay quarry are in line with the literature data, but freeze-thaw experiments on Boom Clay samples seem desirable in order to proof the transferability of the literature data to Boom Clay.