The Slovak Carpathians Loess Sediments, Their Fabric and Properties

Abstract

Based on investigation of the Slovak Carpathian loess soils it appears that the loess mass is composed of various primary rock fragments and minerals, products of their secondary changes and different organic substances. These components were incorporated in loess soils under various conditions. They are diversely distributed both horizontally and vertically depending on the terrain relief, the climate, the degree of dissection, the water table level and other factors. The fabric of loess not only reflects the sediment’s genesis, but also affects its engineering geological properties. Four basic groups of loess sediments have been characterized. These are: typical loess, sandy loess, clayey loess and loess-like sediments. They differ from each other by their fabric, microstructure, genesis, physical and mechanical properties, tendency to collapse etc. Collapse tendency is one of the most significant properties of loess deposits. It is caused by a sudden volume change under the influence of humidity, stress or loading. To explain the mechanism of loess collapse, laboratory modelling of the process has been carried out in a triaxial cell, monitoring the microstructural changes. The results of the laboratory investigations of stress strain behaviour of collapsible loess under two types of triaxial tests are presented and analysed. The effect of stress level and stress path on the strength parameters has been investigated in a series of drained triaxial tests carried out on undisturbed samples of Mnesice loess.