Application of the laser diffraction method for classification of soils by particle size distribution

Goal. To study the possibility of using the laser diffraction method to classify soils by particle size distribution, and the transition from the two-part classification of soils used in Ukraine to the international three-part classification. Methods. Analytical methods were used (determination of soil particle size distribution according to SSU 4730:2007, SSU ISO 11277:2005, and by laser diffraction, analysis of the data obtained). As well as mathematical and statistical (comparison of particle size distribution data). The study was conducted on standard soil samples: SSSU 163.5-2015, ISSU 163.1-2015, ISSU 163.2-2015, ISSU 163.6-2019. Results. It was fixed that the values of the content of fractions of physical clay, determined under SSU 4730:2007 and by laser diffraction using reagents and sample preparation stages described in SSU 4730:2007, differed insignificantly and corresponded to one class of soil according to the modern Ukrainian classification. The difference in the content of fractions established by SSU ISO 11277:2005 and by laser diffraction using reagents and sample preparation stages described in SSU ISO 11277:2005 did not exceed 6%, and in this case, the soil class according to the three-part international classification was the same. Sample preparation in the process of determining the granulometric composition by laser diffraction did not significantly affect the determination of the soil class. Conclusions. The possibility of using data obtained by laser diffraction to determine the soil class using various classifications was proved. To establish the soil class according to the modern Ukrainian classification, it was proposed to use refraction indices for a certain type of soil, determined by approximation of data from the laser diffraction method through data according to SSU 4730:2007. And to establish the soil class according to the USDA/FAO classification, it was proposed to use refraction indices for a certain type of soil, determined as a result of the approximation of data from the laser diffraction method through data established according to SSU ISO 11277:2005.