Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Gy. Czinkota x
  • Refine by Access: All Content x
Clear All Modify Search

Particle size distribution (PSD) is one of the most important fundamental physical properties of soils, as it determines their physical, chemical, mechanical, geotechnical, moreover environmental behaviour. Although the measurement of PSD with different techniques is commonly performed in soil laboratories, their automation and continuous PSD curve generation have not been solved yet.  However, there are some physical principles, various sensors and different data storing methods for measuring the density-time function. In the present paper a possible solution is introduced for the measurement of the soil particle density database as a function of settling time. The equipment used for this purpose is an areometer that is widely used e.g. for determining the sugar content of must, or the alcohol content of distilled spirits, etc. The device is equipped with patent pending capacitive sensors on the neck of the areometer. It measures the changes in the water levels nearby the neck of the areometer in 1 μm units with <10 μm accuracy. The typical water level changes are 3-5 cm, which makes possible a very accurate determination of particle density changes due to settling in particle size analysis. The measured signals are stored in the equipment's memory and can be downloaded to the controller computer via a modified USB port. Data evaluation can be carried out online or later. The large number of measured data points led to the introduction of a new evaluation method, the Method of FInite Tangents or shortly the “FIT Method”. The dispersed soil particle system is considered as the aggregation of many mono-disperse systems. From this it follows that the measured density-time function can be divided into grain size fractions with tangent lines drawn to finite, but optional points. These tangent lines are suitable for calculating the settling speed of a given fraction, as the changing speed of density is equal to the multiplication of settling speed and mass of the given grain size fraction. The settling speed of all fractions is calculable by using the Stokes law, so the mass of all of the floating fraction can be calculated. Because the soil suspension is a poly-disperse system, the measured density decrease can be considered as an integration of finite mono-disperse systems. From this, it follows that it can be interpreted as the sum of linear density vs. time functions. If the mass of each grain size fraction is known, the particle size distribution is calculable. The method is relatively easily programmed and the intervals of grain size fractions are freely adjustable, so with this program almost all types of particle size distribution are calculable, not only those being uniform. Using the appropriate controller and evaluation program, soil particle size distribution can be calculated immediately after downloading the measured data. This technique does not need more sample preparation than past methods. The automated reading lessens the manpower required for performing the measurement - which also reduces human error sources - and provides very detailed PSD data that has advantages, among others, like revealing multi-modality in the particle-size distribution.

Restricted access

Soil texture is an important input parameter for many soil hydraulic pedotransfer functions (PTFs) of the day. Common soil particle-size classes are required to be able to uniformly determine the texture of soils. However, it is not always possible - due to different national classification systems - and much valuable information is disregarded while either deriving or applying PTFs. One way to get common particle-size class information is to interpolate the particle-size distribution (PSD) curve. Advanced interpolation solutions are becoming available, but there is always uncertainty associated with these techniques. Another possibility is to measure all PSD curves in such a way that it is compatible to the commonly used classification systems. A new automated measurement technique is introduced that can easily provide PSD data compatible to any (and all) of the existing national and international classification systems at the same time, without the burden of extra labour. A computerized measurement system has been developed to record density changes in a settling-tube system in any discretional (small) time steps, which in turn allows the derivation of a quasi-continuous PSD curve. The measurement is based on areometry (Stokes-law), thus the system is compatible to the most commonly applied settling-tube measurements. The new evaluation method of measured values takes into consideration the density changes along the areometer-body so it avoids the problem of reference point determination. The theory and setup of the system are explained and measurement examples are given. The presented comparative measurements show good correspondence with conventional settling-tube results, and the reproducibility of the measurement shows to be very high. This technique does not require more sample preparation than past methods. The automated reading requires less manpower to perform the measurement - which also reduces human error sources. However, it provides very detailed PSD data that has advantages, like revealing multi-modality in the particle-size distribution or providing data that complies with any of the classification systems.

Restricted access

For estimating the lime requirement (LR) in some countries it is accepted to use hydrolytic acidity suggested by Kappen, which is based on a single time extraction of hydrogen- and aluminum ion with calcium acetate. More accurate results could be achieved if we measured the total surface acidity (TSA) of soils. For this reason it is an improvement to use a direct measurement method and equipment, which is suitable to estimate the results of long-term processes and TSA, via investigating the kinetic properties of desorption. The method of measurement: A pH electrode is dipped into continuously stirred soil suspension containing background salt (e.g. KCl), and it isconnected to a computer using an amplifier and A/D converter. A computer program has been developed that controls an automatic burette, which adds the base solution into the system if pH is less than the pre-adjusted value (e.g. pH 6.5 or pH 6.8) and stops adding when pH reaches this value. For evaluation, the amount of added base vs. time data series can be used. With increasing time the amount of added base keeps to a constant (asymptotic) value. The program fits an exponential associate function on measured data, and outputs the asymptotic value connected to infinite time, which can be used to calculate LR.  Supposing that there are two processes with different rates, in this case the function can be created as the addition of two first order kinetic sub-processes:  The faster process that takes place on the outer surfaces features easily removable acidity, and the slower process probably describes processes within the deeper pores. The fitting error of parameters is about 0.3-1%, which means that the TSA value, based on these measured data and method can be estimated with high accuracy.  The measurement is fully automated. The evaluation is based on extrapolation, so the precision of results increases with the number of measurement points and the length of measurement time. Depending on the application, a quick measurement with approximate results or a longer measurement with more precise results can be chosen.

Restricted access