Ice lenses at the upper surface of permafrost are growing when seasonally thawing layers (STL) freeze from the bottom. This phenomena occurs in cryogenic geosystems and embank-ments within permafrost regions.

The one-dimensional mathematical model of lower part STL ice layers growth is developed on the base of physical-chemical fundamentals for water crystallization in dispersed soils. Evaluation of the process was done for the geotechniqal and climatic conditions of Yamal peninsula using the mathematical model.

The following detailes of ice lense formation at the seasonally freezing strata bottom are discussed:

• existence of lower and upper limits of heat flow from below, which are the restrictions for ice lense growing conditions;
• existance of lower limit of the water-saturated layer height at the STL bottom which is necessary for ice lense growth;
• greate increasing of the pore water pressure and ice lense growth rate after upper freezing touches the surface of the water-saturated layer at the STL bottom;
• greate increasing of the ice lense growth rate at the clay-sand contact when freezing.

Ice lense growth conditions inside and close to embankments are discussed. It is established that under some real conditions in the lower part of embankments and in the soil base the ice lenses would be growing and embankment stability aggravation could be possible.

S.E. Grechishchev and O.V. Grechishcheva
Earth Cryosphere Institute SB RAS
Russia
From: emelnikov@glas.apc.org (   )