The main purpose of the paper is to present the usefulness of microwave ovens in the everyday work of geotechnical laboratories. Microwave ovens are commonly used to determine soil moisture and to dry soils that are too moist for other laboratory tests. The activities related to the above processes are not standarized in the majority of countries. The only available guidelines are based on the research projects. For the purpose of this particular research 345 tests have been conducted for moisture content determination for 3 soil types: fine sand (FSa; SP - poorly graded sand), sandy gravel (saGr; GW well graded gravel-sand mixtures) and silty clay (siCl; CH - inorganic clay of high plasticity), using both - standard and microwave methods. The research cycle consisted of 3 different variants which includes soil moisture content, specimen initial mass, number of specimens in microwave oven and their placing. It was established that different factors have impact on the length of the process and it lasted between 2 to 17 minutes. During the heating different undesirable phenomena were observed, e.g., soil explosions or melting and glowing of clay. Based on the above research results this paper introduces guidelines for the soil drying process in the microwave oven (the optimization of the procedure and handling of the dried samples).
Brak klarownych wytycznych suszenia mikrofalowego dla określenia wilgotności czy tylko „podsuszania” gruntów przed właściwymi badaniami cech mechanicznych może prowadzić do niekontrolowanych zmian właściwości fizyko-mechanicznych gruntów. W niektórych przypadkach może to grozić nawet „eksplozją” materiału badawczego. Na podstawie licznych i szczegółowych badań wilgotności sformułowano wskazówki na temat optymalizacji parametrów bezpiecznego wykorzystania mikrofalówek w laboratorium geotechnicznym.
EN
The use of microwave drying to determine the water content or only to “pre-drying” of the soils before the proper tests of their mechanical properties, need to be established in detailed way. Without knowledge of the basic criteria for such procedure, may lead to uncontrolled changes in the physical and mechanical properties of soils - even soil “explosion”. On the basis of detailed water content studies, the guidelines were formulated on optimizing the parameters for the safe use of a microwave oven in a geotechnical laboratory.
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