The importance of the geological origin of cohesive deposits in determining their basic geotechnical parameters – liquid limit and liquidity index

Abstract

The liquidity index (IL), as the leading parameter for cohesive deposits, determines the physical condition of the soil and shows clear and important correlations with the mechanical and hydraulic parameters of the subsoil, such as compressibility, shear strength and permeability. In the traditional approach, to calculate the IL value, it is necessary to know the values of three parameters determined in the laboratory: natural moisture content (wn) and the consistency limits: plastic limit (wP) and liquid limit (wL). Various methods of determining these parameters have developed over time. This diversity applies in particular to methods of determining the liquid limit, and to a lesser extent the plastic limit. IL values may vary depending on the methodology used to determine its components, and making comparisons between them is an important issue in engineering geology. The literature on the subject offers proposals for universal correlation relationships between IL or wL values determined on the basis of various research methods. However, a question arises whether such correlations can be created as generalized for all cohesive deposits, or should they have local features and be created for individual genetic groups. As part of this article, laboratory tests were carried out on glacigenic clays of different ages, developed in different facies. Their results show that correlations between the values of the liquidity index vary depending on various laboratory methods used to calculate this parameter.