Osiadanie zapadowe lessów w świetle badań mikrostrukturalnych

Abstract

COLLAPSE IN LOESSES IN THE LIGHT OF MICROSTRUCTURAL STUDIES Summary The paper presents the results of studies on factors determining collapse in loesses, conducted for many years by the present author. Late Pleistocene subaerial loesses and some older ones, occurring within the extent of seasonal frost, were found to be most susceptible for development of this phenomenon. The collapse takes place due to rupture of weak bonds supporting clay bridges between loess aggregates, resulting from the influence of water. This is accompanied by a change in distribution of size of pores. The collapse appears connected with reduction of micro- and mesopores of 1-1000 μm (1 mm) in size and also a part of macropores. The total percentage of these pores is estimated at about a dozen % of the total porosity. Micropores below 1 μm in size do not take part of this process despite of their marked share in the total porosity.