Liquidity index of the Lublin loess as a function of cone resistance qc from CPTU test

Abstract

The paper presents the results of the calibration of an interpretive formula for the determination of IL based on cone resistance qc for loess soils of eolian facies. The studies were carried out on characteristic soils that occur in the Lublin region. For this purpose, three CPTU static soundings were selected in which a representative soil profile with a total length of 21 m was extracted. Boreholes were then drilled in close vicinity, at distances ranging within 1.0 m, and samples for laboratory testing were collected at intervals of 0.25 m. A total of 86 samples were tested and the liquidity index of each was determined. The IL values specified in the laboratory examinations were paired with the cone resistances qc averaged over the depth range corresponding to the sampling. The qc- IL distribution was then analysed and a formula correlating both parameters was derived. The cone resistance depends not only on water content but also on a number of other factors, including porosity, overconsolidation ratio, cementation, fraction distribution, degree of saturation, grain shape and alignment. Therefore, the estimation of IL from CPTU tests should be regarded as an approximation, while an accurate identification of the subsoil requires further investigations. Nevertheless, such information provides valuable knowledge in the initial stages of subsoil recognition, e.g. during design work.