Інженерно-геологічна характеристика порід лесово-ґрунтової серії опорного розрізу Лисогора (Подільська височина)

Abstract

The Lysohora key section is one of the most complete and interesting sections of the loess-palaeosol sequence of the eastern part of Podolian Upland. This is the area where the Pleistocene loess-palaeosol sequence was deposited directly on the rocks of Precambrian crystalline shield, its weathered part (eluvium). The value of engineering-geological research of the section is increasing due to the fact that it is located near the city of Vinnytsia, which has been intensively built up in recent years. We emphasize that in this section Upper Pleistocene loesses play a minor role. The value of the Middle Pleistocene loesses, which are generally poorly studied, is abruptly growing. The Lysohora section was sampled. Above 30 monoliths were taken with the purpose of studying the engineering-geological characteristics of the sediments. Among them are grain size distribution, natural moisture content, plasticity index, soil density, porosity coefficient, subsidence, angle of internal friction, specific cohesion, deformation modulus, chemical composition of aqueous extract, humus content, CaCO3 content, etc. The results of the exploration of the loess-palaeosol sequence properties are correlated with the corresponding stratigraphic horizons of the other sections of Podolian Upland. Besides the main section, which was described in a pit, two additional cuts were studied: one on the Korshiv palaeosol complex, another one on the ice wedge pseudomorphosis of Yarmolyntsi palaeocryogenic stage. It is revealed that loess and palaeosol horizons are very different in their engineering-geological properties. In particular, insignificant subsidence is a characteristic of only individual samples from the upper horizon of the Middle Pleistocene loesses. Palaeosol horizons usually have higher values of density and natural humidity. They have a heavier particle size distribution. According to the analysis of the water extract, the highly soluble salts are practically washed away from the loess-palaeosol series. The significant influence of palaeocryogenesis processes on the formation of engineering-geological properties of rocks is also described. Key words: loess-palaeosol sequence, Pleistocene, engineering-geological characteristic of sediments, palaeocryogenesis.