Engineering-geological characteristic of the sediments of the loess-soil series of the key sections Ternopil and Malyi Khodachkiv (Podolian Upland)

Abstract

Pleistocene periglacial loess-soil series covers the watersheds, watershed slopes and high river terraces of the Volyn-Podolian Upland by the almost continuous mantle of different thickness. A detailed description of two key sections of the loess-soil series of Podillia – Ternopil and Malyi Khodachkiv is given. Both sections are located on the territory of the Ternopil Plateau. The monoliths were taken with the purpose of studying the engineering-geological characteristics of the sediments only from the Upper Pleistocene part of the sections of about 5 m thickness. The following engineering-geological characteristics are defined for the sediments of the described sections: grain size distribution, natural moisture content, plasticity index, soil density, porosity coefficient, subsidence, angle of internal friction, specific cohesion, deformation modulus, the chemical composition of aqueous extract, humus content, CaCO3 content, etc. Integrated analysis of the distribution of parameters of composition and properties of sediments of loess and palaeosol horizons is carried out. It demonstrates their significant difference between certain horizons caused by peculiarities of palaeogeographical conditions of their formation and diagenetic transformation. It is also revealed that the degree of contrast of parameters of composition and properties of loess and palaeosol horizons in Ternopil and Malyi Khodachkiv sections in comparison with key loess-soil sections of Volhynian Upland is much lower. Evidently, it may be due to the small thickness of stratigraphic horizons. It should be noted that palaeocryogenic processes, in particular, diluvial-solifluction deformations and frost wedging, had a significant influence on the formation of engineering-geological properties of the sediments of these key sections. It is important that the engineering-geological properties of the loess-soil series were studied according to the same method in licensed engineering-geological laboratories. This gave us the possibility of correlating the properties of sediments not only in particular sections but also on the regional scale. The conducted research has not only scientific but also important practical value as the loess-soil stratum everywhere is the object of human economic activity and the parent rock of modern soil, etc. Key words: loess-soil series, loess, palaeosol, engineering-geological characteristic of sediments, key section, Podolian Upland.