Particle size analysis by an automated dynamometer method integrated with an x-y sample changer

Abstract

Methods for determining the particle size distribution (PSD) of soils have been developed for many years and we now have a wide range at our disposal. Despite this, the question of their usefulness and the quality of the results obtained by using particular methods is still open. Among them, historically, the oldest sedimentation methods are still very much employed. The paper presents, developed and consistently modernized by the authors, a method of determining the PSD based on changes in the apparent weight of the float submerged in sedimenting suspension. The apparent weight measurement is performed using a sensitive dynamometer with the piezoelectric effect. Then, it is recalculated into cumulative PSD (CPSD) on the basis of Stoke’s law. The method allows the measurement of PSD in a range of grain diameters from 2 µm to 120–130 µm. The integration of the vertically displacing dynamometer and float with the mixer made it possible to automate. Moving the measuring head in the horizontal plane permitted automatic examination of several samples in one measuring cycle. The device works independently after starting. Of note, the method allows for the determination of many different fractions selected by the user. The results of the tests are saved in the form of a report in pdf or xls format. Verification of the method was carried out by comparing the measured and calculated CPSD values of soils, created by mixing in specified proportions of two components with known particle size distribution. The results obtained by this method show a high repeatability and accuracy. Good agreement with the reference method (pipette) is expressed by the RMSE value of 3.36%.