Engineering geological and geotechnical properties of till soil of the Middle Pleistocene glacial period

摘要

Glacial deposits make up the biggest volume of deposits of the Quaternary system in Lithuania. The deposits of the Medininkai glacial period are spread across the entire territory of Lithuania, but occur on the surface only in the southeastern area. The main purpose of this study is to explore the stiffness and deformation of till soils of the Medininkai glacial period and compare the obtained values with the glacial till soil properties presented in the literature. The triaxial cell apparatus, direct shear apparatus and oedometer test apparatus were used for soil investigation in order to achieve the aim of the study. During the in-situ tests the cone penetration test was performed and the borehole was described. Such physical properties of soil as bulk density and moisture content were evaluated, the plastic and liquid limits were established and the grain size distribution of soil was analysed. The mechanical properties of soil were investigated with several different devices; one-dimensional compression, direct shear and triaxial cell tests were performed. The results showed no significant difference between the data obtained during the triaxial cell test and the data obtained from the direct shear test. A significant difference was noticed between the values of the secant modulus E50 calculated during the triaxial cell test and the values of the oedometer modulus Eoed obtained during the oedometer test and those presented in the literature; therefore these values should be considered very carefully. No significant difference was observed between the values of E50 and Eoed obtained during the oedometer test by applying the similar loading intervals. The comparison of Eoed values calculated during the cone resistance test with the results obtained during the E50 and Eoed oedometer test led to similar results. A summary of the results regarding the mechanical properties of till soils of the Medininkai glacial period shows that values obtained by different laboratory methods may be correlated, but may be rarely compared with values presented in the literature.