Determination of soil grain size composition by measuring apparent weight of float submerged in suspension

Abstract

A b s t r a c t. Texture is one of the most significant physical properties of soils. Over the years, several methods of its measuring were developed. The paper presents a method for determining the particle size composition of soils, based on the separation of particles in the sedimentation process. Density of suspension is determined on the basis of apparent weight changes of a float submerged in it. The weight of the float suspended on a thin line, at a given depth in the suspension, is measured with a sensitive piezoelectric dynamometer. The Stokes equation is used to calculate the content of soil fractions with equivalent diameters in the range of 0.001 to 0.1 mm. Digital transmission of results from the dynamometer, the temperature sensor and measurements of the distance defining the depth of immersion of the float to the computer enable calculations of particle size composition to be performed automatically. This paper presents the results of measurements of the particle size composition of artificially generated mixtures of 'silt' and 'clay'. The results are compared with results obtained with other methods (including the laser method). A high level of repeatability of the results and satisfactory compatibility in relation to the reference pipette method are noted.

Soil grain size analysis by the dynamometer method – a comparison to the pipette and hydrometer method

“…As can be seen in Figure 4 and as shown in the paper of Kaszubkiewicz et al (2017), results of measurements of the same fraction in the dynamometer method may vary by 2-4% depending on the measurement depth, and depending on the sample weight varies by 1 to 6%. Larger differences could be observed for larger depths of measurements.…”

“…The use of new measurement method obviously raises the problem of comparability of results with that obtained so far, the quantity of accidental and systematic errors and test result repeatability. The first tests of the method showed its satisfactory compliance with the results obtained in the pipette method and correctness of results for artificially prepared soil mixtures (Kaszubkiewicz et al 2017).…”

“…The method for determination of grain size distribution in the range of 0.002-0.1 mm diameters proposed by Kaszubkiewicz et al (2017) gives a satisfactory compatibility of results with the results of the pipette method considered as a reference as well as the hydrometer method. There is no need to enter the calibration of dynamometer method to achieve the convergence of results with the pipette method.…”

“…In the case of pipette and hydrometer method, the methodology described in the work of Ry¿ak et al (2009) has been applied. The dynamometer method is described in Kaszubkiewicz et al (2017). It consists in determining the density changes of the suspension at a depth z in time t by measuring the apparent weight of the float immersed in it.…”