Abstract
Clay content is the main characterizing parameter when classifying fine-grained soils. Hydrometer method (HD) is commonly used in geotechnics to obtain the grain size distribution properties of fine-grained soils. However, this test is laborious and time consuming as compared to alternative methods such as laser diffraction (LD). In this study, a comparison between the results for clay content of 19 samples from different locations in Finland using HD and LD methods was carried out aiming at obtaining a mathematical expression that allows to transform LD measurements into HD results. The results were statistically compared showing significant differences between the results of these two techniques and underestimation of the clay content by the LD method was observed. Based on the results, the reliability of the laser method in the determination of clay content is discussed.
Highlights
Particle size distribution of soils is an important characteristic affecting soil properties such as compressibility, frost susceptibility and water transport and retention
In agreement with the results obtained by various previous studies comparing the hydrometer and laser method, our results show a consistent underestimation in the clay content percentage by the laser diffraction method
No reliable regression model was obtained for laser diffraction and hydrometer results due to the poor correlation between the investigated methods
Summary
Particle size distribution of soils is an important characteristic affecting soil properties such as compressibility, frost susceptibility and water transport and retention. Particle size distribution of finegrained materials in geotechnical engineering has been traditionally determined by hydrometer method (HM) or pipetting. The main objective of the hydrometer analysis is to obtain the clay content (percentage finer than 0.002 mm), which controls the classification of fine-grained materials (soil name). As an alternative to the methods previously mentioned, laser diffraction method (LDM) might be used for particle size analysis of fine-grained soil samples. The results are obtained significantly faster, in a wider range of size and with less human intervention. If the result are to be used for geotechnical design, its calibration against hydrometer method is required, according to standard EN 1997-2:2007 [1]
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